

What’s a virus? What is a harmful virus? What is Trojan? Do the Trojan Horses automatically infect the systems? What is Worm? Though I did not run the executable file of an e-mail, is there still a possibility of being infected? GIF ya da JPEG dosyalarına virüs gizlenebilir mi? Though I did not download a program from a web site, is there still a possibility of being infected? My friends tell me that they receive infected e-mail messages from me, although my computer is not infected by a virus. Is it possible? Are HOAXES harmful? Are there viruses that affect specific versions of Windows operating systems? How do the anti-virus programs operate? I heard about online virus scanners. What is their address and how do they run? Is a licensed anti-virus program available in METU? I want to download McAfee’s update files. What’s the address for download? What’s a virus? It is an intentionally written small program that causes computers to behave in a harmful way not appropriate to their designated function and without the awareness of the user Top What is a harmful virus? Viruses are categorized and assessed as harmful by the anti-virus companies according to their rate of propogation, according to to the damage they do to computers, and according to its intensity of occurence in its medium of propogation (Internet) Top What is Trojan? Programs that creates backdoor giving permissions to run a code in the computer from another one. Top Do the Trojan Horses automatically infect the systems? This is not possible today. Unless the trojan horses are run by the user or the e-mail reading program, they do not do any harm. However, it is obvious that people try to write programs that are inserted in directories that provide full network sharing fetaure Top What is Worm? Programs that are using the security holes of the operating system or working services of computer to infect it automatically are called as worm. Top Though I did not run the executable file of an e-mail, is there still a possibility of being infected? Yes indeed. Some e-mail reading programs (MS Outlook and MS Outlook Express) run some specific file extensions automatically. MS has released a security patch file in 2001 to remedy this vulnerability. MS Outlook and MS Outlook Express users that did not download this patch file are vulnerable and defenseless to many viruses that emerge. Top Can a virus "hide" in a GIF or JPEG file? Answer is NO, but there are virus files that seems as GIF or JPEG file. Usually they have two extension with a second extension that is shown by the e-mail browser program. Threfore these GIF or JPEG files are thougt as normal GIF or JPEG files and executed by the user and usully an error mesage or a picture displayed on the screen. However virus is started to work in background. Top Though I did not download a program from a web site, is there still a possibility of being infected? Yes. Through .dll files (useful for ActiveX) or Java applets downloaded from the web pages visited may infect your system with a virus. If the security settings of the user web browser is not set to the medium or highest, the files mentioned above are downloaded and run by the browser without prompting the user. Top My friends tell me that they receive infected e-mail messages from me, although my computer is not infected by a virus. Is it possible?* Two factors may explain this situation. Either your computer is infected with a virus and you were not alerted about it since you did not update your anti-virus software against latest viruses; or although your computer is actually NOT infected, a computer keeping your address in its address book may have been infected with W32/Klez virus and that virus may have written your address on the “From:” part of the e-mail message and send it to other users available on that address book. You need the “full header” information to find out the genuine sender of these e-mail messages. Top Are HOAXES harmful? As long as they propogate a feeling of being real, they exploit the ignorance of users and they cause harm to systems. For example, some e-mail messages deceive the users and make them delete harmless programs used by the operating system manually. Top Are there viruses that affect specific versions of Windows operating systems? Yes, there is. The main factor for that kind of infection is not actually the version of the OS but the file system that the OS uses. For example, Win9x /ME use FAT32 file system and WinNT/2000//XP use NTFS file system. NTFS system does not allow anybody or any program (except for the users that are granted authorisation) to enter information on some parts of the local disc. For that reason, the virus programs cannot enter information on system files or registry files. Top How do the anti-virus programs operate? The anti-virus programs operate according to three different structures. Most widely used “Scanner” type of anti-virus programs gather information about the latest viruses via latest update files and they trace the known virus patterns that change the strucure of the files. If they detect a virus, they perform the virus-specific tasks that are predefined on their data files against viruses. “Check-summers” type of anti-virus programs try to detect the modifications in size of standard operating system files and they alert the user if a modification takes place. Although it seems that “Check-summers” type of anti-virus programs are favorable since they do not need updating, they are complex programs that can be competently used only by anti-virus experts and that may sometimes display false warning messages. “Herustic” type of anti-virus programs try to detect viruses by using the characteristic structures of viruses defined on these programs. Top I heard about online virus scanners. What is their address and how do they run? Symantec Inc and Network Assoc. provide online virus scan service. To access these sites, follow one of these paths; http/www.symantec.com/avcenter --> Check for Security Risk --> Scan for virüs http://www.mcafee.com --> VirüsScan Online After you perform the necerssary procedures to allow the site to scan your computer, a program is installed on your computer. Next, all of your files are scanned for viruses. If this program detects a virus, it tries to clear your system from that virus. Top Is a licensed anti-virus program available in METU? Yes. McAfee VirüsScan 4.5.1 program is licensed as campus license. Top I want to download McAfee’s update files. What’s the address for download? Download and run the most recently added Sdat****.exe file on ftp://ftp.metu.edu.tr/popular/virus-updates/mcafee/ address to update your anti-virus software. Click here to find detailed information. Top