Abstract: A string detection system preferably includes a buffer for receiving data and parsing that data into strings, and a content addressable memory, connected to the buffer, for receiving the strings and comparing each string with entries in the content addressable memory. This string detection system may be incorporated in an intrusion detection system that monitors a data stream addressed to a host device or network. In an intrusion detection system, the string detection system monitors the data stream for strings which match attack signatures.

Abstract: The Remote SONET/SDH Loopback (RSL) is an optical network interface device consisting of a facility interface 24, a drop side interface 26, a facility receive signal splitter 12, a drop side receive signal splitter 18, an idle signal generator 16, a command logic assembly 10, and a switching circuit assembly 22. The RSL addresses the need for a low-cost sub-section layer device by efficiently processing the SONET signal to support only loopback and idle signal generation. The RSL may be provisioned to either loopback the facility or generate an idle signal when the drop side of the termination is disconnected, turned-off, or has otherwise failed to generate a valid signal. The SONET signal may also be looped back upon itself when a user controlled loopback command code is detected within the SONET overhead. The RSL otherwise passes the SONET signal unaltered. The RSL may be provisioned by the user to specify the location and characteristics of the embedded loopback command codes.