Computer virus

Computer virus is a program that can spread across various computers or network by itself, making copies without the user’s knowledge. They cause harm to the system. The virus infection may be displaying irritating messages, stealing data or giving the control of your system to another person. How does it affect the system??? . A virus program has to be executed before it takes over the control. They can attack themselves to the other programs or hide in code that will run automatically when particular program is started. Sometimes they cause a fatal damage to the operating system and spreading itself throughout the system automatically. The virus is also attached as the email attachment and when the user tries to open it. The system is affected by it. Virus scanners detect viruses and disinfect them from damage. The anti-virus can be on-access or on-demand. On-access scans the every application tried to open detecting the changes in the system. Where as on- demand scanners scans the system only when it is demanded.