Alert levels (sometimes called "severity levels") help you choose how to respond to viruses, spyware, and other potentially unwanted software. While Microsoft Security Essentials recommends that you remove all viruses and spyware, not all software that is flagged is malicious or unwanted. Whenever it detects a potential threat, Microsoft Security Essentials assigns that item one of the following alerts levels: Severe, high, medium, or low (for more information, see Understanding alert levels).