stealth virus

Typically, when an antivirus program runs, a stealth virus hides itself in memory, and uses various tricks to also hide changes it has made to any files or boot records. The virus may maintain a copy of the original, uninfected data and monitor system activity. When the program attempts to access data that's been altered, the virus redirects it to a storage area maintaining the original, uninfected data. A good antivirus program should be able to find a stealth virus by looking for evidence in memory as well as in areas that viruses usually attack.

The term stealth virus is also used in medicine, to describe a biological virus that hides from the host immune system.

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