See also: Bad Things | Bad Code | Cracker
So called malicious code is usually a piece of software that does Bad Things to data. For example delete or even worse alter data. The authors of such code are usually Bad Guys. This sort of code flourishes on the internet where there are many users lacking security knowledge.
Examples for malicious code:
Terms used in that context: Exploit, Backdoor, Buffer Overflow, Hack, hpvac, Cracking, AV software, Social Engineering, Harden and Getting Rid Of Spyware.
Maybe there are some Good uses for malicious code. You would have to ask a Malicious User.
TakeDown.NET -> “Malicious-Code”