Computer Virus is a self-replicable malware that could spread throughout the infected system by injecting itself into a legitimate program or file. It typically consists of three components: infection mechanism, payloads, and triggers.
It can be detected by spread detection and analyse detection. To bypass such detections, Virus can utilise several obfuscation techniques such as encryption, act benign (using Trojan Horse as a shell), lay dormant, or simply infect slowly. The payloads of the virus could be different every time it spread to a new victim, which will confuse the antivirus even more. Virus usually doesn’t output anything to avoid alerting the user that execute it.
When programming a Virus, make use of comment markers to identify the start and the end of a payload.