A computer virus is an infiltration that corrupts existing files on your computer. Viruses are named after biological viruses, because they use similar techniques to spread from one computer to another.
Computer viruses mainly attack executable files and documents. To replicate, a virus attaches its “body“ to the end of a target file. In short, this is how a computer virus works: after execution of the infected file, the virus activates itself (before the original application) and performs its predefined task. Only after that is the original application allowed to run. A virus cannot infect a computer unless a user, either accidentally or deliberately, runs or opens the malicious program by him/herself.
Computer viruses can range in purpose and severity. Some of them are extremely dangerous because of their ability to purposely delete files from a hard drive. On the other hand, some viruses do not cause any damage - they only serve to annoy the user and demonstrate the technical skills of their authors.
It is important to note that viruses (when compared to trojans or spyware) are increasingly rare because they are not commercially enticing for malicious software authors. Additionally, the term “virus” is often used incorrectly to cover all types of infiltrations. This usage is gradually being overcome and replaced by the new, more accurate term “malware” (malicious software).
If your computer is infected with a virus, it is necessary to restore infected files to their original state - i.e., to clean them by using an antivirus program.
Examples of viruses are: OneHalf, Tenga, and Yankee Doodle.