You may notice one day that your computer is sluggish, not responding to commands. Your browser homepage has changed, your search page has changed, or you are no longer able to connect to the Internet. What’s going on?
Your machine may have a virus. A virus is a computer program file that can attach to disks or computer files and replicate itself without your knowledge or permission. A virus might run when the file it infected runs, or it might sit in your computer’s memory and infect files as your computer works with them. Viruses can be intentionally destructive, or they may just be annoying. One example of a virus is the Melissa virus, released in 1999. This virus spread around the globe in under 24 hours, clogged e-mail systems, and inserted quotes from the Simpsons TV show into documents.
Your machine may have a worm. A worm is a sub-class of a virus, and it is more common today than a virus. It can replicate without your help, like an e-mail address book attack. Worms do not infect other computer files on your machine. Worms are usually spread through e-mail. One example of a worm is the Anna worm, released in 2001. An e-mail with an attachment of a picture of tennis player, Anna Kournikova, was sent out, but the attachment was really a worm. When the attachment was opened, the worm sent one copy of the worm to each e-mail address in Outlook’s address book. This worm was relatively benign.
Your machine may have a Trojan horse. This is a program that seems to be good, but is really harmful, and does something you do not expect. It can erase your computer data, corrupt your files, spread other viruses and worms, spy on your keystrokes, or install a backdoor on your system. Trojan horses are usually spread through e-mail, and contained in an attachment. One example of a Trojan horse is the Amanda Trojan, which is contained in an executable attachment. Once the attachment is run, the Trojan tries to connect to a specific Internet address and gives a hacker remote control access over the infected machine. The main goal of this Trojan is to steal personal confidential information.
Your machine may be full of spyware. A spyware program collects information about you without your consent, such as your bank account numbers, passwords, etc. Almost all of these programs are bad. A particularly bad type of spyware is the toolbar program Hotbar. This program allows you to apply skins to program windows, menus, mail, and other applications. After you install it, it records all the Internet activities of all users on the installed computer and adds the information to its database. The program periodically sends the information in the database “home.” Even if you remove Hotbar, it leaves pieces that allow it to reinstall itself if they are not removed manually.
There are several things you can to do stop or slow the infection and spread of viruses, worms, Trojan horses, and spyware.