Computer Viruses   A computer virus is a computer program that can copy itself and infect a computer without knowledge of the user. A virus is spread from one computer to another when its host is taken to an uninfected computer, for instance over a network or from a floppy disk, CD, or USB drive. Additionally, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by another computer. Viruses are sometimes confused with computer worms and Trojan horses. A worm can spread itself to other computers without needing to be transferred as part of a host. A Trojan horse is a file that appears harmless until executed. Some viruses are programmed to damage the programs, deleting files, or reformatting the hard disk. Others simply replicate themselves. Even these benign viruses can create problems by taking up computer memory. As a result, they often cause erratic behavior and can result in system crashes. A virus may also send a web address link as an instant message to all the contacts on an infected machine. If the recipient, thinking the link is from a friend (a trusted source) follows the link to the website, the virus hosted at the site may be able to infect this new computer and continue propagating. Many users install anti-virus software that can detect and eliminate known viruses. They work by examining the content of the computer's memory and the files stored on fixed or removable drives (hard drives, floppy drives), Users must update their anti-virus software regularly to patch security holes and to combat the latest threats. One may also prevent the damage done by viruses by making regular backups of data (and the Operating Systems) on different media, that are either kept unconnected to the system (most of the time), read-only or not accessible for other reasons, such as using different file systems. Another method is to use different Operating Systems on different file systems. A virus is not likely to affect both. Once a computer has been compromised by a virus, it is usually unsafe to continue using the same computer without completely reinstalling the operating system. However, there are a number of recovery options that exist after a computer has a virus. As a last ditch effort, if a virus is on your system and anti-viral software can't clean it, then reinstalling the operating system may be required. To do this properly, the hard drive is completely erased and the operating system is installed from an uninfected media. Important files should first be backed up, if possible, and separately scanned for infection before erasing the original hard drive and reinstalling the operating system. Back to Tip of the Month

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