Network Intrusion Detector ( http://ciac.llnl.gov/cstc/nid/nid.html )
One of CIAC's Tools Development Group's works ( CTDG ). It provides a suite of security tools that detects and analyzes network intrusions. NID provides detection and analysis of intrusions from individuals not authorized to use a particular computer, and from individuals allowed to use a particular computer but who perform either unauthorized activities or activities of a suspicious nature on it. The NID software product is available free of charge to all U.S. Government agencies.