A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code. If this replication succeeds, the affected areas are then said to be “infected” with a computer virus. Computer viruses generally require a host program. The virus writes its own code into the host program. When the program runs, the written virus program is executed first, causing infection and damage. A worm does not need a host program, as it is an independent program or code chunk. Therefore, it is not restricted by the host program but can run independently and actively carry out attacks.
Effects and Identify of Computer Virus
- Reduce System Speed.
- Pop-up Windows.
- Self Execution of Programs.
- Log out from Accounts.
- Crashing of the Device.
Types of Computer Virus
Discussed below are the different types of computer viruses:
- Boot Sector Virus: It is a type of virus that infects the boot sector of floppy disks or the Master Boot Record (MBR) of hard disks. The Boot sector comprises all the files which are required to start the Operating system of the computer. The virus either overwrites the existing program or copies itself to another part of the disk.
- Resident Virus: A virus that saves itself in the memory of the computer and then infects other files and programs when its originating program is no longer working. This virus can easily infect other files because it is hidden in the memory and is hard to be removed from the system.
- Multipartite Virus: A virus that can attack both, the boot sector and the executable files of an already infected computer are called a multipartite virus. If a multipartite virus attacks your system, you are at risk of cyber threat.
- Overwrite Virus: One of the most harmful viruses, the overwrite virus can completely remove the existing program and replace it with the malicious code by overwriting it. Gradually it can completely replace the host’s programming code with the harmful code.
- Polymorphic Virus: A polymorphic virus changes its code each time an infected file is executed. It does this to evade antivirus programs.
- File Infector Virus: This common virus inserts malicious code into executable files — files used to perform certain functions or operations on a system.
- Spacefiller Virus: It is a rare type of virus that fills in the empty spaces of a file with viruses. It is known as cavity virus. It will neither affect the size of the file nor can be detected easily.
- Macro Virus: A virus was written in the same macro language as used in the software program and infects the computer if a word processor file is opened. Mainly the source of such viruses is via emails.