Computer virus

Introduction
       
        While viruses can be intentionally destructive (for example, by destroying data), many other viruses are fairly benign aur merely annoying. Some viruses have a delayed payload, which is sometimes called a bomb. For example, a virus might display a message on a specific day or wait until it has infected a certain number of files or computers. A time bomb occurs during a practicular data or time and a logic bomb occurs when the user of a computer takes an action that triggers the bomb.
            However,the predominant negative effect of viruses is there uncontrolled self reproduction, which wastes aur overwhelms computer resources.

Antivirus software

               Antivirus software consists of computers  programs that attempt to identify, thwart and eliminate computer viruses and other malicious software (malware). Antivirus software typically uses Two different techniques  to accomplish this.
                 • examining(scanning) files to looks for known bhai Rajesh matching definitions in a dictionary.
                   • identifying suspicious behaviour from any computer program which might indicate infection.
          Most commercial antivirus software uses both of these approaches, with an emphasis on the virus dictionary (pattern) approach.

Virus dictionary approach
                    In the virus dictionary approach, when the antivirus software examines a file, It refers To a dictionary of known viruses that the authors off the antivirus software have identified. If a piece of code in the file matches any virus identified in the dictionary,then the antivirus software can take one of the the following actions (in order by favoorability):
                      • attempt to repair the live by removing the virus itself from the file.
                       • Quarantine the file (such that the file remains inaccessible to other programs and its virus can no longer spread),
                        • delete the infected file.

Computer virus
                 
                  To achieve consistent success in the medium and long term, the virus dictionary approach requires periodic (generally online) download of updated virus dictionary entries. As cicically minded and technically inclined users identify new viruses "in the wild", they can send their infected files to the authors of anti-virus software, who then include information about the new viruses in there dictionaries.
                  Dictionary based antivirus software typically examines files when the the computers operating system creates, opens, closes or E-mailed them. In this way Eid can detect a known virus immediately upon receipt.