what is Virus

                                              Computer virus

• A computer virus is a program,  macrodesigned to damage, steal personal information, modify data, send e-mail, display messages, or some combination of these actions. When the virus is executed, it spreads by copying itself into or over data files, programs, or the boot sector of a computer's hard drive. Virus writers use detailed knowledge of security vulnerabilities to gain access to a host's computer.in other words we can say that A computer virus or a computer worm is a malicious software program that can self-replicate on computers or via computer networks – without you being aware that your machine has become infected.

• Virus can be devided according to their method to attack or infect your computer 

File viruses
Boot sector viruses
Macro viruses
Script viruses 

Now question is how protect our self from the attack of these computer virus and worms 

• you install anti-malware software on all of your devices – including Personal computers, laptopsand smartphones – and that your anti-malware solution receives regular updates, in order to protect against the latest threats