Virus can be defined as the weakness of the system . Virus makes a system more vulnerable to the attacker . Viruses are made to threaten the target system.
Virus is a kind of malicious program which is used to harm the target system . When virus is executed into the target system , generally it replicates itself in many copies and infect the target system . A computer virus infects data files or program or information stored into the target system.
Some viruses are designed in such way that they utilize the disk space and make it unavailable resulting into fragmentation. Viruses may harm the system in many ways like stealing personal information , infecting the documents and data stored , stealing boot records and many other possibilities are there
Viruses contain the property to install themselves without the permission of user. However , hiding property in viruses differs according to their work and use. Virus writers mainly code the virus for destructive purposes, generally to exploit system and infect the data stored . Sometimes a virus can also be used for pranking and fun.
Viruses have tendency to change their nature by automatically modifying their source code and sometimes this gives as advantage to the virus . It generally hides itself using encryption or using alternate data streams ( discussed in previous chapters)
Generally a computer virus , first get executed into the system and then starts infecting the target system. Once it replicates and successfully infects the target system. Ultimate aim of a computer virus is corrupt the system . A virus may corrupt the whole system and make it un-accessible.