A computer virus can be regarded as any software or activity that produces unwanted results in computing devices, irrespective of the kind or severity of the resulting damage. While some computer viruses may render a device completely unusable, others may cause financial losses or it can merely be an irritating factor. That is why pranks and even chain letters or spam should be prevented by antivirus software.

Antivirus (or anti-virus) software is used to prevent, detect, and remove malware, including computer viruses, worms, and trojan horses. Such programs may also prevent and remove adware, spyware, and other forms of malware.

A variety of strategies are typically employed. Signature-based detection involves searching for known malicious patterns in executable code. However, it is possible for a user to be infected with new malware in which no signature exists yet. To counter such so-called zero-day threats, heuristics can be used. One type of heuristic approach, generic signatures, can identify new viruses or variants of existing viruses by looking for known malicious code (or slight variations of such code) in files.

Some antivirus software can also predict what a file will do if opened or run by emulating it in a sandbox and analyzing what it does to see if it performs any malicious actions. If it does, this could mean the file is malicious.

Some antivirus programs are actually malware masquerading as antivirus software, such as WinFixer and MS Antivirus. It is therefore advisable only to purchase antivirus software from a reputable antivirus provider and brand.

A false positive is identifying a file as a virus when it is not a virus. If an antivirus program is configured to immediately delete or quarantine infected files (or does this by default), false positives in essential files can render the operating system or some applications unusable. The end result is just as unwanted as the results produced by a virus and such software can therefore be placed in the same category as a computer virus. Certain antivirus firewall software, such as the AVG Free Version has a reputation for false positives.

Running multiple antivirus programs concurrently can also degrade performance and create conflicts. It is sometimes necessary to temporarily disable virus protection when installing major updates such as Windows Service Packs or updating graphics card drivers. Active antivirus protection may partially or completely prevent the installation of a major update, however disabling protection even for a short period, can create the opportunity for a virus to execute its code. It is therefore advisable to reboot a computing device and run an antivirus scan, before doing a system or software upgrade.

ADDITIONAL INFORMATION

Wikipedia
Scamalertnetwork