System and method for using signatures to detect computer intrusions

A system and method are disclosed for detecting intrusions in a host system on a network. The intrusion detection system comprises an analysis engine configured to use continuations and apply forward- and backward-chaining using rules. Also provided are sensors, which communicate with the analysis engine using a metaprotocol in which the data packet comprises a 4-tuple. A configuration discovery mechanism locates host system files and communicates the locations to the analysis engine. A file processing mechanism matches the contents of a deleted file to a directory or filename, and a directory processing mechanism extracts deallocated directory entries from a directory, creating a partial ordering of the entries. A buffer overflow attack detector compares access times of commands and their associated files. The intrusion detection system further includes a mechanism for checking timestamps to identify and analyze forward and backward time steps in a log file.