Computer virus can be thought of as malware programmes that are designed such that when ever they tend to execute, they replicate themselves. This is done by them by inserting copies of them into different other programs, data and even files or the boot sector of the hard drive. The areas in the computer are said to be infected once this replication has occurred.
These viruses are designed such that they often perform some harmful activity on the host such as they often steal the disk space, or the CPU time of a healthy computer. They also harm by accessing private information, corrupting data, displaying humorous or other messages on the home screen and in many other ways.
But overall all viruses do not attempt to hide themselves or harm the computer. The main characteristics of a virus is that it self replicates and are computer programs that install themselves without users consent.
The virus programmers or writers use the concept of social engineering ans also exploit the detailed knowledge of security venerability to gain access to their host computing resources. The vast number of computer virus target the running Microsoft windows, and they employ a variety of mechanisms to infect new hosts, and often also use complex anti-detection algorithm just to evade the different anti-virus programs.
The computer virus in recent times are causing damage of billions of dollars of economy every year. This they achieve by giving system failure, file corruption and many other factors like data corruption, increasing the maintenance costs etc. In the response of such problem free and open source anti-virus softwares have been developed. This has given a huge growth to the multi-billion dollar industry of anti-virus companies. These companies sell virus protection tools to other companies and organizations who are in need of protecting their systems and files from these computer virus. The android and windows OS are the most effected ones by these viruses. Unfortunately we presently don’t have any such virus protection software that can catch all kind of viruses as the virus definitions change day by day.
Types of Computer virus:
According to the infection targets and replication techniques the viruses can be divided or classified into the following groups:
1. Resident vs. non-resident viruses:
Resident viruses install themselves as part of RAM. Non-resident viruses infect the disks and hard drive and then exist in them.
2. Macro Viruses:
Macro viruses are written in macro languages and then attached to documents. So, when ever these documents are executed they also get executed and start infecting.
3. Boot Sector viruses:
These computer virus as suggests by the name attack the boot sector of the computer and then exists and harms there.
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