PGP Desktop TCP - Free Essay Example

Task-1:-PGPPage-5-To-14 Problem statement Download PGP Desktop software.. Experiment with new installation using the following features: 1.Key management .. 2.Securing E-mail Messages 3.Securing Instant Messaging . c) Experiment and report on the remaining option available under the licence.. Task-2:- TCP/IP SecurityPage-15-To-20 Problem statement Why TCP/IP Network are considered unsecured. Describe the following technologies: SSL (Secure Socket Layer).. IPSec (IP Security). Kerbaros.. Task-3:- Hardware and softwarePage-21-To-26 Problem statement Differences between Windows NT,Windows XP and UNIX Differences between HIDS and NIDS Task-4:- Buffer overrunsPage27-To-32 Problem statement How a variety of overruns and format string bugs can alter the program flow on program. Five methods of causing havoc by unauthorized altering of memory using a buffer overflow. THREE C++ functions ONE well-recognized method of preventing buffer overflow. Solution Task-1 Experiment with new installation using the following features: 1.Key management 2.Securing E-mail Messages 3.Securing Instant Messaging 1.Key management: Whenmanaged by a PGP Universal Server, PGP Desktop 9.x provides a secure recovery mechanism for private keys, called KeyReconstruction. As its name suggests, Key Reconstruction can be used to reconstruct (or restore) your private Key if you have forgotten its passphrase, or if you have deleted your private Key . To take advantage of Key Reconstruction, you send Key reconstruction data to a reconstruction server (a PGP Universal Server that is managing your PGP Desktop)while you stillhave your private Key and remember its passphrase. The reconstruction data for your private Key consists of five questions, that you may create, and five answers that only you know. After you have sent your reconstruction questions and answers to the server, you may reconstruct your private Key at any time by answering 3 of the 5questions correctly. If you have deleted your private Keyor forgottenits passphrase before sending reconstruction questions and answers to the server, you cannot regain your private Key using KeyReconstruction. If you need help understanding any of the concepts mentioned above, please read the following Crypto Concepts section. Otherwise, feel free to skip down and Reconstruct your private Key Crypto Concepts Private Key When you install PGP Desktop you are prompted to create a keypair, which is comprised of two related keys: a public Key and a private Key Your private Key is used for decrypting something that was encrypted using your related public Key, as well as generating digital signatures that can be verified using your public Key As its name suggests, your private Key. should be kept totally private, and should be protected by a strong passphrase. Key Reconstruction For detailed technical information about Key Reconstruction, please refer to the white paper Inside PGP Key Reconstruction (from the PGP Corporation White Papers). Reconstruct Your Private Key Click the PGP Tray lock icon in your system tray and then click Open PGP Desktop: Click the PGP Keys control box. Select the keyring that contains your Key Click the Key that you wish to reconstruct: To reconstruct a private Key, you must have its associated public Key on your keyring. If you dont have a copy of your public Key, you might try downloading it from a Keyserver, such as your PGP Universal Server or the PGP Global Directory. Otherwise, contact your administrator to obtain a copy of your public Key Now click the Keys menu andclick Reconstruct: Answer 3 of the 5 Key reconstruction questions correctly, then click OK: The answers are case sensitive, and must be entered precisely as they were when you first sent them to the server. If you are certain that nobody can see your screen, you might want to check the box labeled Show Keystrokes, so that you can verify your answers. After you have answered 3 of the 5 Key reconstruction questions correctly, you must enter and confirm a new passphrase for your private Key , then click OK: When you are notified that Key reconstruction was successful, click OK: 2.Securing Email Messages When PGP Messaging is enabled, you will find that PGP will begin encrypting your E-mail accounts by default. This will occur when you open your E-mail application for the first time after installing PGP Desktop 9.x, and you send/receive E-mail. If you are communicating with other PGP users through E-mail PGP Desktop can automatically encrypt and sign Messages to PGP users depending on the policies that have been set within PGP Desktop under the Messaging section. PGP Desktop does configure default policies if you do not wish to create your own. These default encryption policies will be reviewed in Section 3 of this document. New encryption policies will be described in Section 4 of this document. Enable PGP Messaging PGP Messaging is enabled by default during installation. However, if you disabled PGP Messaging during installation, there are two ways to enable this feature. They are as follows: Locate the PGP Desktop icon (padlock) in the system tray. Click the PGP Desktop padlock and click Use PGP E-mail Proxy. The option will have a black check mark next to it when it is enabled. Open PGP Desktop through the Programs/All Programs menu and select the Tools menu. Click Use PGP E-mail Proxy. The option will have a black check mark next to it when it is enabled. Assign a PGP Key to a PGP Messaging Service PGP Messaging requires a PGP Key to secure the E-mail account(s). To assign a key to a messaging service for the first time, do the following: When you open your E-mail application for the first time after installing PGP Desktop, PGP will display the E-mail Account Detected window after sending/receiving mail. Select Yes, secure this E-mail account, and then click Next. You may select one of many key sources. If you created a key pair during installation, then generally, the option you would select is PGP Desktop Key. You can also create a new key pair, or import a previously exported key pair. After choosing the source, click Next. Highlight the key to be used for this E-mail account and click Next. Click Finish. You are now ready to encrypt mail through this E-mail account and proceed with section 3. Review Default E-mail Encryption Policies Two encryption policies are set by default. These policies are: Require Encryption: [PGP] Confidential. This policy specifies that any message flagged as confidential in your E-mail client or containing the text [PGP] in the subject line must be encrypted to a valid recipient public key or it cannot be sent. Opportunistic Encryption. Specifies that any message for which a key to encrypt cannot be found should be sent without encryption (in the clear). Having this policy the last policy in the list ensures that your Message will always be sent, albeit in the clear, even if a key to encrypt it to the recipient cannot be found. Do not put Opportunistic Encryption first in the list of policies (or anywhere but last, for that matter) because when PGP Desktop finds a policy that matches, and Opportunistic Encryption matches everything, it stops searching and implements the matching policy. So if a policy is lower on the list than Opportunistic Encryption, it will never be implemented. The list of policies is read from the top down, so be sure to put Opportunistic Encryption last in the list. The default policies Require Encryption: [PGP] Confidential and Opportunistic Encryption cannot be modified or deleted, but they can be disabled. Create New E-mail Encryption Policies If you would like to create additional encryption policies, the steps to do so are described as follows: Open PGP Desktop. Locate the PGP Messaging control box on the left. This will display different configured services and the Messaging Log options. Within the PGP Messaging control box, select a configured service (e.g. [emailprotected]/* */). The settings for the service appear in the PGP Messaging work area, including the list of existing security policies. This is the right hand pane. Click New Policy in the PGP Messaging Control box OR pull down the Messaging menu and click New Messaging Policy. After the Message Policy dialog appears, enter a description of the policy in the top field offered. Specify the conditions to be met and the action to be performed. Specify a course of action to take if the recipient key is not found. For detailed descriptions of the available conditions and actions, please refer to your PGP Desktop Users Guide (.pdf). This is located in StartProgramsPGPDocumentation. Policies are applied in the order that they are listed. You can change the order by highlighting the policy you wish to move and clicking the up or down arrow at the bottom of the Security Policies window to move it. Understanding the PGP Messaging Log The PGP Messaging Log, located in the PGP Messaging control box, is instrumental in describing the actions taken by PGP Messaging in processing E-mail . View Log For: This item at the top left will allow you to view the logs of the current day or up to seven days past. Just select the day you wish to view. View Level: This option in the upper right will allow you to view logs related to general information, warnings, error Message , and may even be set to verbose for greater detail of each item previously mentioned. Saving Daily Log If you wish to save the log file for a specific day, display the correct day and click Save at the bottom of the Messaging Log work screen. Specify the location to save the file and click Save again. Shred Log Use the Shred Log option to clean the contents of the Messaging Log for the currently displayed day. 3.Securing Instant Messaging AIM sessions between two systems running PGP Desktop 9.x are protected automatically when PGP Desktop 9.x is installed and the PGP AIM Proxy is enabled. Both AIM users MUST have PGP Desktop 9.x installed for the session to be encrypted. It is not sufficient that one user have PGP Desktop installed. Both must have the AIM Proxy enabled. Both users also have to be added to the buddy list in the AIM settings. Enable PGP AIM Proxy The PGP AIM Proxy is enabled by default if the option was not unchecked during installation. If the proxy is disabled, there are two ways to enable it. These methods are as follows: Click on the PGP Desktop padlock in the system tray. Click Use PGP AIM Proxy. The option will have a check by it when enabled. Open PGP Desktop through StartProgramsPGP menu. Pull down the Tools menu, and click Use PGP AIM Proxy. How to Know the Session is Encrypted When the option is enabled you should see an alert in the system tray which states PGP Desktop Secured AOL Instant Messenger session for [screen name] has started. Additionally, other users will see a padlock next to your screen name. You. will see in the conversation a note that the conversation is being encrypted by PGP Desktop. Solution Task-2 a) Why TCP/IP Network are considered unsecured. W hen TCP/IP was designed in the early 1980s, security was not a primary concern. However, in the years since their inception, the lack of security in the TCP/IP protocols has become more of a problem. The widespread use and availability of the TCP/IP protocol suite has exposed its weaknesses. Presented here are a number of well-known vulnerabilities of both TCP/IP itself, and of some protocols commonly used along with TCP/IP (such as DNS). TCP SYN attacks IP Spoofing Sequence Guessing Source Routing Connecting Hijacking Source Routing Connecting Hijacking Desynchronization during connection establishment Desynchronization in the middle of a connection Routing (RIP) attacks ICMP attacks DNS attacks The lack of unique identifiers a) TCP SYN attacks In an Internet environment, high message latency and loss are not uncommon, resulting in messages that arrive late or in nonsequential order. The TCP half of TCP/IP uses sequence numbers so that it can ensure data is given to the user in the correct order, regardless of when the data is actually received. These sequence numbers are initially established during the opening phase of a TCP connection, in the three-way handshake. SYN attacks take advantage of a flaw in how most hosts implement this three-way handshake When Host B receives the SYN request from A, it must keep track of the partially opened connection in a listen queue for at least 75 seconds. This is to allow successful connections even with long network delays. Figure: SYN Flooding b) IP Spoofing IP Spoofing is an attack where an attacker pretends to be sending data from an IP address other than its own [Morris85, Bellovin89]. The IP layer assumes that the source address on any IP packet it receives is the same IP address as the system that actually sent the packet it does no authentication. c) Sequence Guessing The sequence number used in TCP connections is a 32 bit number, so it would seem that the odds of guessing the correct ISN are exceedingly low. However, if the ISN for a connection is assigned in a predictable way, it becomes relatively easy to guess. This flaw in TCP/IP implementations was recognized as far back as 1985, when Robert Morris described how to exploit predictable ISNs in BSD 4.2, a Unix derivative [Morris85]. Figure :IP Spoofing via Sequence Guessing d) Source Routing Another variant of IP spoofing makes use of a rarely used IP option, Source Routing. Source routing allows the originating host to specify the path (route) that the receiver should use to reply to it. An attacker may take advantage of this by specifying a route that by-passes the real host, and instead directs replies to a path it can monitor Although simple, this attack may not be as successful now, as routers are commonly configured to drop packets with source routing enabled. Figure : Source Routing Describe the following technologies: 1) SSL (Secure Socket Layer) 2) IPSec (IP Security) 3) Kerbaros Secure Sockets Layer (SSL) The Secure Sockets Layer (SSL) protocol was developed by Netscape Communications, and enables secure communication over the Internet. SSL works at the transport layer of Transmission Control Protocol/Internet Protocol (TCP/IP), which makes the protocol independent of the application layer protocol functioning on top of it. SSL is an open standard protocol and is supported by a range of both servers and clients. SSL can be utilized for the following: Encrypt Web traffic using Hypertext Transfer Protocol (HTTP). When HTTP is utilized together with SSL, it is known as HTTPS. SSL is generally utilized to authenticate Web servers, and to encrypt communications between Web browsers and Web servers. Encrypt mail and newsgroup traffic. SSL provides the following features for securing confidential data as it transverses over the Internet: Authentication Data integrity Data confidentiality through encryption The SSL handshake process is described below: The client initiates the SSL handshake process by sending a URL starting with the following: https:// to the server. The client initially sends the Web server a list of each encryption algorithm which it supports. Algorithms supported by SSL include RC4 and Data Encryption Standard (DES). The client also sends the server its random challenge string which will be utilized later in the process. The Web server next performs the following tasks: Selects an encryption algorithm from the list of encryption algorithms supported by, and received from the client. Sends the client a copy of its server certificate. Sends the client its random challenge string 2. IPSec (IP Security) IPsec (Internet Protocol Security) is a framework for a set of protocols for security at the network or Packet processing layer of network communication. Earlier security approaches have inserted security at the application layer of the communications model. IPsec is said to be especially useful for implementing virtual private networks and for remote user access through dial-up connection to private networks. A big advantage of IPsec is that security arrangements can be handled without requiring changes to individual user computers. IPsec provides two choices of security service: Authentication Header (AH), which essentially allows authentication of the sender of data, and Encapsulating Security Payload (ESP), which supports both authentication of the sender and encryption of data as well. The specific information associated with each of these services is inserted into the packet in a header that follows the IP packet header. Separate key protocols can be selected, such as the ISAKMP/Oakley protocol. Security architecture IPsec is implemented by a set of cryptographic protocols for (1) securing packet flows,mutual authentication and establishing cryptographic parameters. The IP security architecture uses the concept of a security association as the basis for building security functions into IP. A security association is simply the bundle of algorithms and parameters (such as keys) that is being used to encrypt and authenticate a particular flow in one direction. Therefore, in normal bi-directional traffic, the flows are secured by a pair of security associations. Kerberos : Kerberos is An Authentication Service for Computer Networks. When using authentication based on cryptography, an attacker listening to the network gains no information that would enable it to falsely claim anothers identity. Kerberos is the most commonly used example of this type of authentication technology. Modern computer systems provide service to multiple users and require the ability to accurately identify the user making a request. In traditional systems, the users identity is verified by checking a password typed during login; the system records the identity and uses it to determine what operations may be performed. The process of verifying the users identity is called authentication. Password based authentication is not suitable for use on computer networks. Passwords sent across the network can be intercepted and subsequently used by eavesdroppers to impersonate the user. While this vulnerability has been long known, it was recently demonstrated on a major scale with the discovery of planted password collecting programs at critical points on the Internet . Authentication, Integrity, Confidentiality, and Authorization Authentication is the verification of the identity of a party who generated some data, and of the integrity of the data. A principal is the party whose identity is verified. The verifier is the party who demands assurance of the principals identity. Data integrity is the assurance that the data received is the same as generated. Authentication mechanisms differ in the assurances they provide: some indicate that data was generated by the principal at some point in the past, a few indicate that the principal was present when the data was sent, and others indicate that the data received was freshly generated by the principal Solution Task-3 rock-solid for years. Differences between Windows NT,Windows XP and UNIX UNIX is an operating system which was developed by Bell Labs, which was a subsidiary of the American Telephone and Telegraph company. UNIX was written to run the computers which control telephone switches, and is designed to use the least amount of memory possible. As far as I know, there is no Graphical User Interface, or GUI, available for use with UNIX. Widows is an operating system designed by Microsoft, and is made to be used as a GUI. The early versions of Windows, up through Windows 2000, used Microsoft Disc Operating System, or MS-DOS, to carry out the commands initiated by pointing at an icon and clicking on it. Windows XP uses a new operating system, NT, which was also designed by Microsoft, to carry out those commands. A Windows user uses a mouse to point at icons, select them, and open them. These operations are performed without having to enter any code into the computer, because the program generates the code when the mouse is clicked on the icon. UNIX requires that the user input code to perform any operation, and this code usually includes address specifications, processing instructions, and and output address specifications. Difference between Windows and UNIX web hosting Windows and UNIX are in fact two different systems and of course we are But Windows servers have also its positive sides, they are compatible with Microsoft applications, and fully support Microsoft FrontPage, Microsoft Access and MS SQL, they also offer advance-programming environments and features such as Active Server Pages (ASP), the ASP.NET framework, Visual Basic Scripts, MS Index Server, Macromedias and Cold Fusion. Windows operating system require little or no experience in web development to get advanced features working very quickly because of better graphical user interface (GUI) Software such as Microsofts FrontPage is specially developed for the webmaster to decrease the website development time and efforts. Lets go back again to UNIX, they support FrontPage, Flash, Shockwave, Real Audio/Video, Cgi Scripts, Perl, PHP, SSH (Secure Telnet), MySQL, Web-Based Control System, Anonymous FTP, Web Site Graphical Statistics, Web-Based Email System, Miva/XML, Cold Fusion Perl, JAV A, PHP, C, C++, Miva, Shell Access and other wide verity of feature like Telnet and SSH that provides lots of flexibility and freedom in managing file and directories, but some of this require advance knowledge of Unix commands in order for you to customize the scripts to match your website needs. Because of the nature of UNIX, (open source) and the people who love it, there is on the WWW freely available software and scripts, again bringing the cost down. Concluding which one is the best, it really depends what you need, if you need high uptime, security and not so expensive then go with UNIX, if you need to run Windows applications like, MS Access or the MS SQL SERVER then Windows is your choice. Difference between Windows and UNIX programming cultures This post on Slashdot links to an article on comparison between UNIX and Windows programming cultures. However, it mostly talks of how the problem of usability is approached. Id like to take a different tack, in the difference between the API of the two systems. Windows APIs are huge. In the Microsoft world, everything seems to end up being part of the core OS services somehow. This has the advantage that you dont need to expect people to have such-and-such library. Or does it? Changes to what is the core between OS versions make compatibility somewhat nightmarish; youre never quite sure what libraries are there or not. Writing installers is a mess. MSI helps, but not if theres no MSI package for the libraries. Another side-effect of this is that Windows programmers are always learning a zillion new things. Win32 services. COM. COM+. .NET. DNA. TAPI. The list goes on and on. Many of those APIs do the exact same thing, so learning the new one is only needed because the old one becomes obsolete. Its hard to stabilize such a huge API. Core Win32 APIs have no consistent reporting. OK, this drove me up the wall when I was coding on that platform. Does the MoveWindow() return NULL or INVALID_HANDLE on error? How about CreateFile()? And whats up with the ridiculous conventions for WaitForMultipleObjects()? Sure, GetLastError() is there, but so many APIs set this (including, say, MessageBox()) that many programs end up reporting an error as The operation completed successfully. UNIX APIs tend to return ints, -1 on error with errno set, a positive integer otherwise. Period. Windows SendMessage is stupid. Granted, with MFC and such, you dont need to look at it as much. But whats the big idea of passing two parameters of a known bit-width for every message? Why not pass a void* pointing to a different struct for each message? The result: huge pain when porting from Win16 to Win32, and another huge pain that will occur when porting from Win32 to Win64. No wonder they want to move to .NET. Compare to X-Window, which uses the void* approach, and you have to admit that SendMessage() and the WindowProc() conventions are mis-designed. Some Windows services are strangely tied to physical windows. For instance, many COM calls dont work if theres no window and no message loop. This is documented, but its a pain in the ass for multithreaded programming. Ditto for timers; IIRC theres no way portable to Win98 that lets you have a timer callback without a message loop. Compare to UNIX setitimer. UNIX threading is a mess. This has improved somewhat in recent years, but I still run into problems. Linux and glibc are the big culprits there. They have changed their threading strategies several time, and each time a glitch appears, we get a finger-pointing match between the kernel and glibc team. This is annoying to say the least. At least one widely-distributed Linux distro (RedHat 9) exhibits severe problems under load, due to bugs in the glibc that are partly made worse by the JDK. In my view, threading should be a kernel service (and Im not completely alone in this viewit seems the Linux kernel is moving more and more towards that model) and it should remain stable, dammit. Sure, you could do similar things with fork(), but thats not a reasonable approach with a GC runtime. In contrast, Win32 threading has been Differences between HIDS and NIDS Host Intrusion Detection (HIDS) This real-time monitoring device alerts the administrator when a specific event has occurred such as a new user being added or any abnormal usage patterns. Host intrusion detection software detect threats aimed at your critical hosts or servers. Network Intrusion Detection(NIDS) NIDS primary responsibility is to monitor, detect and identify malicious activity on a network. Once suspicious activity is detected, an alert is generated for each activity. Comparative analysis of HIDS vs. NIDS Function HIDS NIDS Comments Protection on LAN **** **** Both systems protect you on your LAN Protection off LAN **** Only HIDS protects you when you are off the LAN Ease of Administration **** **** The admin of NIDS and HIDS is equal from a central admin perspective. Versatility **** ** HIDS are more versatile systems. Price *** * HIDS are more affordable systems if the right product is chosen. Ease of Implementation **** **** Both NIDS and HIDS are equal form a central control perspective Little Training required **** ** HIDS requires less training than NIDS Total cost of ownership *** ** HIDS cost you less to own in the long run Bandwidth requirements on (LAN) 0 2 NIDS uses up LAN bandwidth. HIDS does not. Network overhead 1 2 The NIDS has double the total network bandwidth requirements from any LAN Bandwidth requirements (internet) ** ** Both IDS need internet bandwidth to keep the pattern files current Spanning port switching requirements **** NIDS requires that port spanning be enabled to ensure that your LAN traffic is scanned. Update frequency to clients **** HIDS updates all of the clients with a central pattern file. Cross platform compatibility ** **** NIDS are more adaptable to cross platform environments. Local machine registry scans **** Only HIDS can do these types of scans. Logging *** *** Both systems have logging functionality Alarm functions *** *** Both systems alarm the individual and the administrator. PAN scan **** Only HIDS scan you personal area networks. (unless you have the $ to get a NIDS for your home) Packet rejection **** Only NIDS functions in this mode. Specialist knowledge *** **** More knowledge is required when installing and understanding how to use NIDS from a network security perspective. Central management ** *** NIDS are more centrally managed. Disable risk factor * **** NIDS failure rate is much higher than HIDS failure rate. NIDS has one point of failure. HIDS and NIDS Advantages: HIDS Advantages: The primary advantage of NIDS is that it can watch the whole network or any subsets of the network from one location. Therefore, NIDS can detect probes, scans, malicious and anomalous activity across the whole network. These systems can also serve to identify general traffic patterns for a network as well as aid in troubleshooting network problems. NIDS also is not able to understand host specific processes or protect from unauthorized physical access. NIDS Advantages: HIDS technology does not have the benefits of watching the whole network to identify patterns like NIDS does. A recommended combination of host and network intrusion detection systems, in which a NIDS is placed at the network border and an HIDS is deployed on critical servers such as databases, Web services and essential file servers, is the best way to significantly reduce risk. Solution Task-4 How a variety of overruns and format string bugs can alter the program flow on program. b. Five methods of causing havoc by unauthorized altering of memory using a buffer overflow. c. THREE C++ functions ONE well-recognized method of preventing buffer overflow. How a variety of overruns and format string bugs can alter the program flow on program. A buffer overflow occurs when a program or process tries to store more data in a buffer (temporary data storage area) than it was intended to hold. Since buffers are created to contain a finite amount of data, the extra information which has to go somewhere can overflow into adjacent buffers, corrupting or overwriting the valid data held in them. Although it may occur accidentally through programming error, buffer overflow is an increasingly common type of security attack on data integrity. In buffer overflow attacks, the extra data may contain codes designed to trigger specific actions, in effect sending new instructions to the attacked computer that could, for example, damage the users files, change data, or disclose confidential information. Buffer overflow attacks are said to have arisen because the C programming language supplied the framework, and poor programming practices supplied the vulnerability. In July 2000, a vulnerability to buffer overflow attack was discovered in Microsoft Outlook and Outlook Express. A programming flaw made it possible for an attacker to compromise the integrity of the target computer by simply it sending an e-mail message. Unlike the typical e-mail virus, users could not protect themselves by not opening attached files; in fact, the user did not even have to open the message to enable the attack. The programs message header mechanisms had a defect that made it possible for senders to overflow the area with extraneous data, which allowed them to execute whatever type of code they desired on the recipients computers. Because the process was activated as soon as the recipient downloaded the message from the server, this type of buffer overflow attack was very difficult to defend. Microsoft has since created a patch to eliminate the vulnerability. (b) Five methods of causing havoc by unauthorized altering of memory using a buffer overflow. A Hybrid Method of Defense against Buffer Overflow Attacks: (1) Stack Guard : The Stack Guard compiler is the most well known dynamic method of defense against buffer overflows attacks. It is designed to detect and stop stack based buffer overflows attacks targeting the return address on the stack. It guards the return address by placing a dummy value (canary value) between the return address and the stack data just before transferring control to a function. StackGuard protection can be subverted if the attacker can guess the dummy value, or by abusing a pointer to the return address. (2) Stack Shield: This is a compiler patch for GCC , which is also based on the idea of protecting the return address on the stack. It implements three types of protection; two of them defend against overwriting of the return address and one against overwriting of function pointers. It basically implements all of them using auxiliary stacks or global variables to maintain copies of the original contents i.e. contents before function calls and then compares the respective contents before returning control, to determine if the return address or function pointers have been tampered with. (3) Propolice : Propolice is a GCC patch [7] that is perhaps the most sophisticated compiler based protection mechanism. It borrows the idea of protecting the return address with canary values from StackGuard. Additionally it protects stack allocated variables by rearranging the local variables so that character buffers are always allocated at the bottom, next to the old base pointer, where they cannot be over flown to harm any other local variables. (4) Libsafe/Libverify : This tool is similar to the solution proposed in this paper as it also provides a combination of static and dynamic protection. Statically it patches exploitable buffer manipulations functions in standard C library. A range check is done by a safe wrapper function before proceeding with the actual operation, which ensures that the return address and the base pointer cannot be overwritten.. (5) LibsafePlus: This is a newly developed tool for runtime buffer Overflow protection. The idea of their protection method is similar to that presented in this paper; that is they first collect the size information of buffers in the program and then use it to detect overflows via function call interception as in Libsafe. They use a tool called TIED: Type Information Extractor and Depositor. (c) Describe at least THREE C++ functions : Canary-based defenses. Non-executing stack defenses. Other approaches. Canary-based defenses Researcher Crispen Cowan created an interesting approach called StackGuard. Stackguard modifies the C compiler (gcc) so that a canary value is inserted in front of return addresses. The canary acts like a canary in a coal mine: it warns when something has gone wrong. Before any function returns, it checks to make sure that the canary value hasnt changed. If an attacker overwrites the return address (as part of a stack-smashing attack), the canarys value will probably change and the system can stop instead. This is a useful approach, but note that this does not protect against buffer overflows overwriting other values. 2. Non-executing stack defenses Another approach starts by making it impossible to execute code on the stack. Unfortunately, the memory protection mechanisms of the x86 processors (the most common processors) dont easily support this; normally if a page is readable, its executable. A developer named Solar Designer dreamed up a clever combination of kernel and processor mechanisms to create a non-exec stack patch for the Linux kernel; with this patch, programs on the stack can no longer be normally run on x86s. It turns out that there are cases where executable programs are needed on the stack; this includes signal handling and trampoline handling. Trampolines are exotic constructs sometimes generated by compilers (such as the GNAT Ada compiler) to support constructs like nested subroutines. Solar Designer also figured out how to make these special cases work while preventing attacks. 3. Other approaches There are many other approaches. One approach is to make standard library routines more resistant to attack. Lucent Technologies developed Libsafe, a wrapper of several standard C library functions like strcpy() known to be vulnerable to stack-smashing attacks. Libsafe is open source software licensed under the LGPL. The libsafe versions of those functions check to make sure that array overwrites cant exceed the stack frame. However, this approach only protects those specific functions, not stack overflow vulnerabilities in general, and it only protects the stack, not local values in the stack. Their original implementation uses LD_PRELOAD, which can conflict with other programs. (d) ONE well-recognized method of preventing buffer overflow: Preventing Buffer Overflows Buffer overflow vulnerabilities are the result of poor input validation: they enable an attacker to run his input as code in the victim. Even when care has been taken to validate all inputs, bugs might slip through and make the application insecure. This article presents the various options available to protect against buffer overflows. These methods either check for insecure function calls statically, look for overflow during runtime dynamically or prevent execution of code on the stack. Non-executable stack: In this method the stack is configured not to hold any executable code. Kernel patches are available for both Linux and Solaris for configuring a non-executable stack. Data execution prevention in Windows XP and 2003 also protect the stack against buffer overflow. This method protects against stack-based buffer overflow attacks. Static Analysis: In static analysis the source code is parsed for dangerous library calls and race conditions to detect potential buffer overflows. Functions like strcpy and sprintf are vulnerable to buffer overflows, so source code scanners are used to look for incorrect use of these functions. RATS and SPLINT are two such tools; however static analysis is riddled with false positives. Dynamic runtime protection: Buffer overflow conditions are detected during the actual running of the program in this method, and an attack thwarted. Different techniques of dynamic runtime analysis are: Canary: When a function call is made, a canary is added to the return address; if a buffer overflow occurs, the canary will be corrupted. So, before returning to the parent function, the canary is checked again to see if it has been modified. Stack Guard uses this technique by implementing it as a patch to the GCC complier; this causes minimum performance delays. Free BSD also has a patch available to do this. Copying Return Address: In this method, the return address is saved separately; so even when a buffer overflow exploit overwrites the return address on the stack, it is set back to the original value when the function returns.

Essay Topics For High School Research Paper Topics

<h1>Essay Topics For High School Research Paper Topics</h1><p>Have you been approached to compose an exploration paper at your secondary school? It very well may be exceptionally scary to discover a subject and begin composing. In the event that you have never composed an examination paper, it is significant that you set aside the effort to get the entirety of the data together. You need to have the option to finish this paper without an issue and make a decent grade.</p><p></p><p>The best thing that you can do when composing an examination paper is to attempt to recollect however much as could reasonably be expected. This is on the grounds that you have to think of a particular subject that you will talk about. You will likewise need to consider the sort of paper that you will be giving. At the point when you compose a theme in your examination paper, you need to consider how much data you need to incorporate. You can utilize this data as a guide for you to start with.</p><p></p><p>Many understudies like to have a theme decision in their exploration paper. They have thoughts and they need to expound on them. At the point when you consider subjects for your exploration paper, you need to pick something that has a topic to it. This will support you on the off chance that you compose the exploration paper and need to get it affirmed by the school. There is nothing more regrettable than revamping an examination paper since you didn't pick a theme.</p><p></p><p>Once you have picked a subject or two, you will need to begin to consider where you need to begin composing your exploration paper. This ought to be where you can oversee it. Have an arrangement of what you are going to discuss. How are you going to consolidate that data into the paper? Have some data all set that you can start with.</p><p></p><p>You should incorporate a rundown of research quest ions and the exploration that you have done on them. Incorporate everything that youhave done in your schoolwork task. This is a path for you to mention to the remainder of the class what you think about the subject.</p><p></p><p>You may likewise need to discuss where you have found support. For instance, you can talk about how you discovered data about the point. Help could be from another person or just from one's own thoughts.</p><p></p><p>One approach to give yourself thoughts for exposition subjects is to record addresses that you might want to see replied in your examination paper. Along these lines, you can consider the themes and consider answers that are out there. These answers will assist you with having a thought on the things that you need to remember for your paper. At the point when you do this, you will be bound to get an exposition that will make a decent grade.</p><p></p><p>These tips will assi st you with getting thoughts for article themes and to keep yourself propelled to concoct the correct subjects. You ought not constrain yourself to writing in a specific time span. You ought to compose whatever you can consider, yet attempt to be original.</p>

Writing Ancient Greek Essay Topics

<h1>Writing Ancient Greek Essay Topics</h1><p>The thought of composing an antiquated Greek exposition themes is a wellspring of joy for most understudies, however as a general rule, they do not have the experience to compose such an article. Then again, there are some notable journalists who have kept in touch with the absolute best old Greek article topics.</p><p></p><p>When it comes to Ancient Greek history, there are unlimited stories to be told. In any case, in all actuality it is hard to state precisely how old Greek history started, who really achieved it and why. The best way to genuinely get into the quick and dirty of the period is to investigate authentic works and figure out what the contentions were on various sides, just as draw your own conclusions.</p><p></p><p>Of course, the Internet gives individuals incalculable assets to assist them with studying Ancient Greek history. This incorporates looking at on line sites by proficient students of history and people who have survived the period, which give quick guidance on the best way to go to a decision.</p><p></p><p>Once you've had some thought of how the individuals of the time thought, it is currently conceivable to settle on an exposition theme for your Ancient Greek coursework. Just as being an amazing wellspring of data about the occasions, these articles must be written in an intriguing way that can be perused by understudies and kept in their memory. Consequently, many teachers are urging understudies to compose the articles themselves utilizing different devices accessible on the Internet.</p><p></p><p>One of the most famous approaches to get Ancient Greek paper points is by going on the web to message sheets. There are numerous expert message sheets with themes identified with Ancient Greek history where you can post your conclusions and examine what is acceptable and terrible ab out Ancient Greek history.</p><p></p><p>These subjects are regularly extremely near the perspective of individuals who survived the period. Such papers can likewise have proposals about the individuals who are being talked about, permitting you to comprehend the individuals in the period much better.</p><p></p><p>If you need to compose expositions on Ancient Greek history that will demonstrate fruitful, it's suggested that you look for the assistance of somebody encountered in Ancient Greek themes. This will assist you with ensuring that the exposition isn't just fascinating yet that it will likewise be sufficiently convincing to empower you to recall what you have learned.</p><p></p><p>As it turns out, history is a significant piece of all human life. It is imperative to find out about the past so you can ensure that your activities today are reasonable and just.</p>

Which is the Best Topic For This is Believe Essay Topics?

<h1>Which is the Best Topic For This is Believe Essay Topics?</h1><p>There are numerous these is accepted exposition themes to look over. On the off chance that you are uncertain of what sorts of points will be all the more speaking to your cohorts and educators, you can generally utilize the assistance of an instructor or other parent of a youngster. It can assist with talking with educators and different guardians to figure out which are the most mainstream points for this is accepted article topics.</p><p></p><p>To figure out which subject is best for your kid, you have to initially recognize what your understudy's needs are. This is significant since the point for this is accepted exposition subjects ought not be excessively not quite the same as what the understudy is alright with. Accordingly, it will be essential to talk with your youngster and attempt to get them to depict how they feel in their own words about the topic.</p>< ;p></p><p>Once you have decided the subject, you at that point need to choose what kind of introduction you need to give. Contingent upon the evaluation level that your youngster is on, you might need to give a straightforward or a top to bottom introduction. It is ideal to have an introduction with more profundity if the understudy is higher in the evaluation level, yet it can assist with training the understudy to take notes on occasion when they are lower in the evaluation level as well.</p><p></p><p>It is additionally a smart thought to cover the most prevalent views on the subject of this is accepted exposition points. Having the most mainstream views is significant in light of the fact that it can assist with facilitating the understudy's psyche about any conceivable negative meanings that may happen from having these thoughts. For whatever length of time that you spread the most prevalent views, you ought to have the option to guarantee that the understudy realizes that these are a portion of the subjects that they will find out about during this assignment.</p><p></p><p>When picking the most mainstream views on the subject of this is accepted article themes, it will be imperative to examine the entirety of the various points that are basic all through the understudy's life. You can discover what they may think about in school, just as in their regular daily existence. By looking into the entirety of the various zones, you can guarantee that the understudy will have the most obvious opportunity to learn and comprehend the topic of this assignment.</p><p></p><p>Another thing that is significant while picking these is accepted exposition subjects is to guarantee that you likewise keep things as straightforward as could reasonably be expected. Keep the subject straightforward, as basic as could reasonably be expected, yet at the same time keep it speaking to the understu dies. Since this is an alternate point for this is accepted article subjects, it is critical to keep it intriguing and instructive for the understudy to understand.</p><p></p><p>Be sure to rehearse ahead of time what you will do before you give the task. You need to ensure that you can effectively disclose the subject to the understudy with the goal that they don't lose all sense of direction in your composition and the data you are giving. On the off chance that you are utilizing any sort of exposition help that you will be given, it will be essential to peruse it altogether with the goal that you can get any syntactic or spelling blunders before you start your assignment.</p><p></p><p>Remember that the themes for this is accepted paper subjects ought to be both instructive and engaging the understudy. You need to ensure that the understudy has the most obvious opportunity to get familiar with the theme. Also, you need to ensure that you spread the most prevalent views and you are covering the absolute most normal themes that they may be intrigued in.</p>

Call of the Wild Essay Topics

<h1>Call of the Wild Essay Topics</h1><p>For a potential undergrad who is simply beginning to move in the direction of a call of the wild exposition composing degree, call of the wild paper subjects ought to be picked cautiously. An imminent understudy should cautiously read each subject for which the person is composing a call of the wild article. Likewise, the person should be certain that their topic, and the point to which the individual in question is tending to the peruser, are proper to the understudy's call of the wild exposition topic.</p><p></p><p>Call of the wild paper subjects are regularly formal and written in a more conventional style than are standard school papers. The subjects are generally long sections of an article length long and regularly consolidate some conventional English composition. While they are still intended to be utilized as class conversations, the call of the wild paper will for the most part be in first in dividual and will utilize a conversational tone. There are numerous contrasts between the style of call of the wild paper and the style of standard school composing, so it is essential to know the distinction between the two.</p><p></p><p>In a first individual, call of the wild exposition subjects are commonly routed to a solitary understudy, or to one understudy specifically. Likewise with any scholastic composed exposition, the paper will present the individual essayist, and afterward the subject will address their conclusions on the current theme. In a call of the wild article, the call of the wild is typically revolved around a particular occasion, for example, graduation, a wedding, or the beginning of another term at the school. There will frequently be a prologue to the call of the wild exposition points, and afterward a nearby outline of the subject at hand.</p><p></p><p>Call of the wild article themes normally revolve around o ccasions and circumstances that cause the understudies at the school to feel certain feelings or are entangled inwardly. For instance, a call of the wild could be about how an adjustment in the shade of the apartments are causing one to feel awkward. Another call of the wild could be about another style pattern at the school, or a variety of a football match-up that a great deal of understudies are viewing on TV.</p><p></p><p>Call of the wild article subjects are not generally dubious points, yet rather themes that call the understudies at the school insane. For instance, a call of the wild could be about a test that isn't coming until the center of the semester and in this way not permitting understudies sufficient opportunity to finish the task for class. Such a call of the wild exposition may be composed as a task, and understudies would contemplate the guidelines cautiously before composing their own response.</p><p></p><p>Call of the wild articles can likewise be expounded on the school in general. Undergrads can compose a call of the excited about everything from the nourishments that are accessible, to the general environment of the grounds. In a call of the wild exposition, an understudy would expound on the adjustments in the school and how it causes that person to feel about it.</p><p></p><p>Call of the wild articles are extraordinary subjects for exploratory writing classes, since undergrads love their opportunity. Any subject is useful for the call of the wild article, as long as it is written in a powerful way and remembers the essayist's own extraordinary point of view for the theme. It is likewise imperative to take note of that most call of the wild papers can be either composed for an ordinary class or can be utilized as schoolwork assignments.</p><p></p><p>Call of the wild exposition points are once in a while utilized as the call of the wild schoo lwork assignments. Any understudy can utilize these articles as an approach to find out about the understudies at their school, and addition experiences from the creative cycle. Call of the wild articles are anything but difficult to make and can be helpful for any scholastic composing class.</p>

Choosing Colleges Essay Topics

<h1>Choosing Colleges Essay Topics </h1> <h2> What is Really Going on with Colleges Essay Topics </h2> <p>It is conceivable to compose an exceptionally straightforward article on the correct age to cast a ballot or reasonable age to be in a situation to buy liquor. Realities, over the long haul, will consistently win out against how people are feeling at a particular second. For example, you can pick a theme for rudimentary, center, or higher school. Your reaction shouldn't be a book report. </p> <h2> The Truth About Colleges Essay Topics</h2> <p>The primary point of subject decision for a proposition paper is to show the thought can be instituted practically speaking. 1 thing that could help is to begin pondering your decisions early and continue thinking as you get understanding. You've gone to the right spot! The arrangement is, you accept. </p> <p>Tell us a theme you have changed your head on over the most recent t hree years. In the event that quality work is all you need, you should take a gander at allowing us a chance to obey you and offer you with school exposition assist that with willing furnish you with esteem for each and every penny you pay. Pick an unmistakable subject that others may not consider, and whatever you select, verify you know a great deal about it! A lot of understudies make the blunder of endeavoring to re-think what the affirmations people wish to hear in an article, and expound on somethingn't really fundamental to their inclinations and interests. </p> <p>The sports paper is unsurprising and should be maintained a strategic distance from, assuming there is any chance of this happening. For example, a human science educator may give a general theme like the impact of neediness in urban conditions. </p> <h2> A Secret Weapon for Colleges Essay Topics </h2> <p>You're endeavoring to show universities your absolute best self, along these lines it may seem nonsensical to readily recognize a period you battled. The reality, by the by, is that high evaluations in the vast majority of them don't show up so without any problem. Clarify your duties, and you'll be the sort of understudy schools find tremendously alluring. There are bunches of issues, even on your own grounds, that ought to be resolved.</p> <p>Try to recall that the goal of a school confirmations article is to help affirmations officials become acquainted with you. One of the upsides of a private school is the customized consideration regarding help you take the best possible courses, plan for your vocation targets, and find the help to defend your prosperity. A school exposition subject may or probably won't be openly reliant on the understudy dependent on the course and the educator. Maybe you are hesitant to discover help since you were once conned by methods for a trick on-line help. </p> <p>The exposition is completely clear and liquid. A pugnacious paper is a piece of the influence. It's workable for you to fix errors and better your writing in later drafts. So as to be seen, it's imperative to comprehend that there are various exposition subjects which are platitude and abused. </p> <p>Curriculum proposition subjects is a way to attempt. Brain research can gracefully an abundance of intriguing issues to talk about. Innovation is conceivably the most renowned subject to talk about today. </p> <p>Differences between various social classes are firmly connected to deficient income conveyance in the country. It is conceivable to simply expound on your extracurricular interests. School application articles are frequently the most troublesome bit of the application method. One specific significant and fitting subject is innovation. </p> <p>One of without a doubt the most significant components of your school application is your private article. It's consequently essential to warily consider distinctive school article subjects. In certain examples, the school will offer an exposition subject for you. In case you're searching for school paper models, here's an incredible one below.</p> <p>You will be ready to complete every one of your expositions in time, however furthermore secure incredible evaluations on them reliably. Schools can tell at whatever point your paper is essentially a structure exposition. Understudies don't have to expound on a huge defining moment in their article, Soule states. </p>

10 cosas que debes saber sobre formularios del USCIS

Para ser exitoso en peticiones o solicitudes al Servicio de Inmigracià ³n y Ciudadanà ­a   (USCIS) es fundamental llenar correctamente el formulario que corresponda, segà ºn el caso. Para ello, este artà ­culo brinda importante informacià ³n en 10 puntos bà ¡sicos sobre quà © se debe hacer, quà © consejos seguir para evitar problemas graves y cà ³mo hacer un seguimiento de los trà ¡mites una vez que se envà ­a el formulario.   10 cosas que debes saber sobre los formularios del USCIS 1. Las planillas del USCIS son gratuitas y se pueden obtener directamente en la pà ¡gina oficial. Hay decenas de formularios y se debe elegir la correcta, segà ºn el tipo de informacià ³n, peticià ³n o solicitud que se quiere hacer.   En ese enlace anterior se accede a todos los formularios. Para descargarlos es necesario tener adobe reader, el programa que permite abrir archivos pdf. Tambià ©n se pueden buscar por su nombre, que està ¡ siempre conformado por una letra o unas letras (AR, EOIR, G, I, N) seguido por un guià ³n y a continuacià ³n un nà ºmero. Dependiendo del formulario en ocasiones es posible realizar el trà ¡mite online, por ejemplo, para notificar el cambio de domicilio es posible descargar el formulario AR-11 en forma de archivo pdf o tambià ©n cumplir con esa obligacià ³n directamente por internet. Lo que es importe es no enviar doblemente la misma peticià ³n, una por cada medio. 2. Enviar siempre la à ºltima edicià ³n de la planilla. Frecuentemente el USCIS modifica los formularios cambiando alguna pregunta o requisito. Es muy importante fijarse en la fecha que pone expires (expiracià ³n) en la parte superior derecha del formulario.   El mejor consejo es siempre obtener el formulario justo el dà ­a en que se va a completar y asà ­ evitar enviar uno que ha quedado viejo y, por consiguiente, el USCIS no lo va a aceptar. 3. Las planillas deben llenarse en tinta negra. Ademà ¡s, deben estar firmadas a mano por el solicitante de la informacià ³n, solicitud o peticià ³n. A este à ºltimo punto existen dos excepciones. En primer lugar cuando se trata de un menor de 14 aà ±os, en cuyo caso debe firmar uno de los padres o guardià ¡n legal. En segundo lugar, en el caso de personas declaradas judicialmente como incapacitadas, en cuyo caso debe firmar en su nombre su guardià ¡n legal. 4. Es muy importante leer las instrucciones de cà ³mo llenar la planilla ya que allà ­ explican informacià ³n relevante como quà © documentos deben acompaà ±arse al envà ­o el formulario. En este punto hay que tener en cuenta que se envà ­an siempre fotocopias legibles, excepto en los casos en los que expresamente se pide que se envà ­e un documento original. El USCIS puede en cualquier momento solicitar ver dicho documento. Tener en cuenta que si se envà ­a un original, como por ejemplo un pasaporte, el USCIS no lo regresa automà ¡ticamente y habrà ­a que pedirle el retorno oficialmente con su debido formulario. Ademà ¡s, si cualquier documento adicional que es necesario adjuntar està ¡ en un idioma que no es inglà ©s, debe traducirse a ese idioma e incluirse una carta que certifique la traduccià ³n. 5. Mentir expresamente o mediante un omisià ³n es un formulario migratorio es una violacià ³n migratoria y podrà ­a dar lugar a problemas graves. Antes de caer en la tentacià ³n de mentir, consultar con un abogado reputado y entender bien las consecuencias. 6. La tramitacià ³n de casi todos los formularios del USCIS cuestan dinero, aunque hay algunos que son gratuitos. Ademà ¡s, es posible solicitar la exencià ³n del pago segà ºn el tipo de formulario y teniendo en cuenta las circunstancias del solicitante. Es importante verificar esta informacià ³n porque podrà ­a dar lugar a importantes ahorros. Por otro lado, tener en cuenta que no tener dinero no es causa razonable para no enviar un documento al USCIS cuando hay obligacià ³n de hacerlo dentro de un plazo. Por ejemplo, si un novio de ciudadana ingresa a Estados Unidos con una visa K-1, se casan antes de 90 dà ­as pero a continuacià ³n no se solicita la green card por ajuste de estatus porque no se tiene dinero para la cuota, ahà ­ hay un problema muy gordo. 7. Cualquier persona puede llenar el formulario del USCIS por sà ­ misma. Lo importante es que entienda todo lo que pide el formulario y las condiciones. No es aconsejable dejarse llevar por el consejo de amigos o familiares o proceder a llenar la planilla cuando no se comprende todo el trà ¡mite que se inicia. Por otro lado, si se cuenta con un abogado o un representante acreditado, debe cumplimentarse la planilla G-28. Es importante elegir un buen abogado, honesto, con conocimientos y que està © pendiente de las fechas de los casos y de envà ­o de documentos. Conviene desconfiar de todas las personas que ofrecen milagros o que aseguran conocer a una persona dentro del sistema que resuelve problemas a cambio de dinero. Eso, ademà ¡s de ser un delito, es un fraude. 8. Completar solo la parte del formulario que aplica. Algunos documentos sirven para situaciones variadas. Es fundamental que cada uno responda y complete sà ³lo la parte que le corresponde. Por ejemplo, el I-131Application for Travel document, sirve como permiso de reentrada a los Estados Unidos para residentes permanentes, como documento de viaje para refugiados y como advance parole para extranjeros que en el momento de solicitarlo se encuentran fà ­sicamente en Estados Unidos.   Por otro lado, otro problema de confusià ³n puede surgir porque no se elige la variedad correcta de planilla segà ºn la peticià ³n que se quiere hacer. Por ejemplo, el I-129 tiene cuatro modalidades, el I-129, el I-129CW, I-129F e I-129S y sirve para propà ³sitos tan dispares como pedir a un trabajador extranjero o solicitar una visa para el prometido de un ciudadano americano. Es importante no solo elegir el formulario correcto sino tambià ©n completar sà ³lo las categorà ­as que aplican al beneficio que se pide. Y dentro de à ©stas, si alguna respuesta es ninguno contestar NONE y si es No Aplica, por ejemplo en el caso de pedir nombre de cà ³nyuges anteriores cuando se trata de una persona que no los ha tenido, escribir N/A. 9. A la hora de enviar el formulario junto con la documentacià ³n de apoyo y el pago de la cuota al lugar que se indica en las instrucciones se da la opcià ³n de un envà ­o por correo ordinario o por servicio de mensajerà ­a. Cualquiera de los dos es và ¡lido pero, en general, da mayor confianza este à ºltimo servicio por deja constancia de la fecha de entrega. Sin embargo, no es necesario ni obligatorio. 10. Es posible hacer un seguimiento de dà ³nde està ¡n los papeles y cà ³mo va la tramitacià ³n a travà ©s de diferentes medios, desde por internet a llamadas por telà ©fono al Servicio al Cliente del USCIS una vez que se tiene el cà ³digo que identifica al caso. A tener en cuenta En una situacià ³n como la actual es importante que los migrantes en situacià ³n de indocumentados no se presenten voluntariamente en ninguna oficina migratoria ni para recabar informacià ³n ni como acompaà ±antes. Si han sido citados es recomendable presentarse con un abogado. Este es un artà ­culo informativo. No es asesorà ­a legal.