Strangely enough, you may sometimes see an error message that says "This program has performed an illegal operation, and it will be shut down." Don't worry, it does not mean anything illegal happened; it is an incorrect use of the term and is meant to tell you that your computer or a particular program has crashed.

Illegal also refers to "improper use" or "unauthorized access."

See also : privacy  tech support  
NetLingo Classification: Technical Terms