Misuse detectors compare system activity, looking for events or sets of events that match a predefined pattern of events that describe a known attack. As the patterns corresponding to known attacks are called signatures, misuse detection is sometimes called "signature-based detection."
The most common form of misuse detection used in commercial products specifies each pattern of events corresponding to an attack as a separate signature. However, there are more sophisticated approaches to doing misuse detection (called "state-based" analysis techniques) that can leverage a single signature to detect groups of attacks.
Reference:
Old Document:
BACE, Rebecca & MELL, Peter, NIST Special Publication 800-31 on Intrusion Detection Systems, Page 16.
The publication above has been replaced by 800-94 on page 2-4
The Updated URL is: http://csrc.nist.gov/publications/nistpubs/800-94/SP800-94.pdf