Click Log Out. Printing on a Network

Chapter 13 ✦ Accessing the Network You can set the properties on most antivirus programs. In most cases, you can tell the pro- gram to load when you boot the computer and then scan files of various types. You also tell the program how to react to finding a virus — whether to alert you or the entire network, quarantine or delete the infected file, and so on. You also must be careful with antivirus programs. Some programs can cause problems with computer or networking hardware, operating systems, and even other programs on the com- puter. To help guard against problems, buy only reputable brand name antivirus programs. Free antivirus programs are not usually worth the time it takes to download them. If your computer, network, or programs have problems, disable the antivirus program and see if that helps alleviate your trouble. You also might check the Internet for reported problems. Looking closer at viruses Computer viruses infect other programs by copying themselves into the program. They also try to hide within the program by encrypting themselves. Many viruses mutate slightly every time they replicate, so as to escape detection. Viruses can even mutate and replicate from computer to computer on a private network. You have to watch out for all sorts of attacks: viruses, worms, Trojan horses, and even hoaxes. If you have a question about a virus or you need to fix a virus your antivirus program missed, check the Symantec site: www.sarc.com. Nuisances and viruses One of the worst viruses to date is Klez with variations called W32.Klez.Hmm, Klez A, Klez D, Klez E, Klez H, and anything with Klez in the name. This virus is a mass-mailing e-mail worm. Klez is difficult to remove once it gets a hold of your computer. Klez fills the hard drive with trash and garbage while destroying data and overwriting files. Then, it travels across your network easily and efficiently. If you discover a virus on any computer connected to your network, the first thing to do is unplug the cable from the network so the virus cannot travel to other computers. If you’re using a wireless network, turn the infected computer off until you can verify the safety of the other computers. Unplug the access point near the infected computer before turning it back on to apply a fix. Some viruses do more than make copies of themselves: They issue instructions that disrupt the computer’s normal processes. Viruses often use the computer’s clock to trigger the disruption — from displaying a message to crashing a hard disk. The Michelangelo virus is one of those that activates according to the clock: Yearly, on March 6, Michelangelo’s birth- day, the virus takes over your hard disk. There are other types of nuisances, and not all are classified as viruses: ✦ The Melissa virus, for example, is actually a Microsoft Word macro. Macros are mini- programs that run when a file is opened or you actually initiate the macro. Many pro- grams use macros — Word and WordPerfect, for example — and even let you create macros that can make your work easier and help you complete tasks more quickly. However, there are macros that can activate within a program and destroy your docu- ments. Melissa travels in a Word document and is activated only when the document is opened in Word. If you don’t open the document containing the macro, the macro isn’t activated. Melissa is contained in a file attached to e-mail messages. Tip Note Part III ✦ Working with Networked Computers ✦ Programs that Web browsers automatically download from Web sites can modify or delete data or crash your system. Some of these hostile Java applets and ActiveX con- trols can even broadcast your computer data all over the Internet. If you’re using the Internet Explorer, you can set the Security View ➪ Internet Options ➪ Security tab to block Web content that could damage your computer. Other browsers, such as Netscape Navigator, have similar options. ✦ Trojan horses are destructive programs that programmers sometimes hide in normal software. These programs don’t necessarily copy themselves or spread from machine to machine, but they can damage or encrypt your data just the same. ✦ Worms are another type of virus. A worm program enters networked computers and continuously copies itself, consuming resources and hampering network operations as it goes. ✦ Hoaxes are generally sent over e-mail, and they are more a nuisance than anything dan- gerous. The problem with hoaxes is that they often tell you to delete a file to delete the “virus.” Usually those files are files that normally exist in your Windows operating sys- tem; deleting the file can damage Windows. It’s always best to check a reputable Internet site before you take any action touted in an e-mail. Antivirus programs take care of most of the previously mentioned viruses, as long as you keep your definitions up-to-date. Virus distribution Most viruses spread in one of three ways: by attaching to the boot sector of the computer, by attaching to executable files, or as macros mini-programs in documents or spreadsheets. Worms, on the other hand, can ride into your computer on the back of e-mail, executable files, and HTML pages. Worms also ride packets across your network, infecting each com- puter one by one. ✦ Boot sector viruses usually come to your computer on a floppy disk that is also a boot disk. A boot disk is one you insert in the floppy drive and use to start your computer. Certain system files are present, and these files prompt the computer to start up. When you boot your system, the files copy themselves to the boot sector of your hard disk. The boot sector is the set of instructions your computer reads when it starts up. ✦ Program viruses that attach themselves to executable files load themselves into mem- ory when you run the file. The file might have an .EXE or .COM extension, but it also might be a SYS, DLL, BIN, or other file on your system. If you double-click an infected EXE file, such as an animation file you receive from a friend, the virus is activated and spreads through your computer. ✦ A macro virus affects the NORMAL.DOT file a Word or Excel template. When the tem- plate is infected, every document you open in that program also becomes infected. Viruses can work on your system only if you activate them by running the program, opening the document, or booting your system with an infected disk. If you check files and documents first with an antivirus program, you can eliminate the viruses on your system — but only if you keep the program’s virus definitions up-to-date. There are mass-mailing worms that spread through file-sharing networks, such as Kazaa and IRC. These worms attempt to deactivate an antivirus program running on your computer. The best way to stop these viruses is to keep your definitions up-to-date. Tip Chapter 13 ✦ Accessing the Network Looking at antivirus programs Many antivirus programs are on the market today. Many of them are inexpensive, reliable, and safe to use. You also can get virus upgrades for most programs over the Internet. Before buying an antivirus program, you might want to try a demo version of the software. Usually, you can find a demo version on the Internet. Following are some of the more popular and trusted antivirus programs: Norton AntiVirus from Symantec Corporation is popular and dependable. Norton AntiVirus runs in the background and checks e-mail attachments, Internet downloads, files on floppy disks, CD-ROMs, and network files. You also can retrieve new antivirus definitions from Symantec over the Internet. This program costs about 65 per computer, or you can buy a 5- or 10-pack 200 and 400, respectively. Norton is made for Windows and Macs. Symantec also makes the Symantec AntiVirus Corporate Edition for clientserver networks. Install the program to the server and the client. The server schedules live updates of the virus definitions and pushes the definitions or downloads automatically to the clients without the users’ knowledge. McAfee VirusScan from Network Associates includes virus detection, removal, and support services. It scans all drives, boot sectors, file allocation and partition tables, and compressed files. McAfee costs about 50 for one computer, and Network Associates also offers multiple license packs. Macintosh also has various antivirus programs. Norton is available for Macs, as is McAfee. Linux distributions also require virus protection. Vexira AntiVirus is one program available for Linux boxes. F-Prot Antivirus, RAV, and other programs are also available. Check your dis- tribution, and then find a program that works best with that. Finding and applying virus fixes If you use an up-to-date antivirus program, you shouldn’t have too much trouble with a virus getting through to your computer or your network. If, however, you miss an update or a new virus does get by your antivirus program, you can usually get a fix for the virus within a cou- ple of days of the appearance of the virus. Again, if one computer on the network contains a virus, disconnect that computer from the network until you get the fix. Symantec’s site — www.sarc.com — offers fixes for most viruses that you can download from the site and apply to your computer. Make sure you check for the Windows or the Mac ver- sion of the fix, and do read all instructions. Many fixes involve just running the fix file you download. Other fixes involve manually removing the virus and its parts from your computer. If you must work in the Registry of Windows, for example, make sure you make a backup of the Registry before beginning. If you think an e-mail that has been sent to you might be a hoax, make sure you check it out before sending it on to everyone in your address book. You can check the Symantec site or check this government site about hoaxes: http:hoaxbusters.ciac.org. Note