Antivirus software (or anti-virus) is computer software used to identify and remove computer viruses, as well as many other types of harmful computer software, collectively referred to as malware. While the first antivirus software was designed exclusively to combat computer viruses (hence "antivirus"), modern antivirus software can protect computer systems against a wide range of malware, including worms, rootkits, and Trojans.Anti-virus software typically uses two different techniques to accomplish this:Examining files to look for known viruses by means of a virus dictionary and Identifying suspicious behavior from any computer program which might indicate infection. Most commercial anti-virus software uses both of these approaches, with an emphasis on the virus dictionary approach.

Virus dictionary approach In the virus dictionary approach, when the anti-virus software examines a file, it refers to a dictionary of known viruses that have been identified by the author of the anti-virus software. If a piece of code in the file matches any virus identified in the dictionary, then the anti-virus software can then either delete the file, quarantine it so that the file is inaccessible to other programs and its virus is unable to spread, or attempt to repair the file by removing the virus itself from the file.

Windows eSafe Multipurpose program that provides content filtering (so you can selectively block certain websites from users), an antivirus program, a desktop lockdown program (to prevent unauthorized access to your computer), and an anti-vandalism program to keep malicious worms and viruses from attacking your hard disk. Trialware. (http://www.ealaddin.com) F-Prot DOS-based antivirus program. Freeware. (http://www.f-secure.com/) Mail Cleaner Scans your Outlook or Outlook Express email for viruses hidden as file attachments. If it finds one, the program deletes the suspect email and notifies you of its action. Freeware. (http://www.mailcleaner.com) Norton Antivirus 2000 Well-known leading antivirus program. Trialware. (http://symantec.com) ScripTrap Blocks the running of malicious scripts, such as viruses written with VBScript. Freeware. (http://keir.net/scriptrap.html)

Script Defender Protects against all forms of malicious code (such as macro viruses) that run scripting languages such as VBScript or JavaScript. Freeware. (http://www.analogx.com) SurfinGuard Monitors programs for suspicious behavior; if malicious behavior is detected, SurfinGuard kills the suspect program. Freeware. (http://www.finjan.com) Virus Trap Helps detect and capture viruses by offering "bait" files for viruses to infect. Once a "bait" file has been infected, the program alerts you so you can send the trapped virus to an antivirus company for further analysis. Freeware. (http://www.diamondcs.com.au/) Macintosh Agax An expandable, free antivirus program that offers both standard virus-scanning and more advanced background protection. Freeware. (http://www.defyne.org/agax/) Disinfectant Adds basic virus protection by scanning files when opened and monitoring your system for unusual activity. Freeware. (http://macinfo.its.queensu.ca/MacSDistribution/Disinfectant.html) McAfee VirusScan One of the most popular antivirus programs in the world. Shareware. (http://www.mcafee.com)