Abstract: In an intrusion detection/prevention system, network traffic is received and checked for a matching pattern. Upon identifying the matching pattern, the network traffic with the matching pattern is evaluated against rules that are represented by a rule tree. References to rule options are represented in the rule tree and are stored separately from the rule tree. The rule tree represents unique rules by unique paths from a root of the tree to the leaf nodes, and represents rule options as non-leaf nodes of the rule tree. Evaluating the network traffic includes processing, against the network traffic, the rule options in the rule tree beginning at the root. Processing of the rules represented by subtrees of nodes with rule options that do not match is eliminated. The network traffic is evaluated against rules terminating in leaf nodes only for combinations of rule options that match the network traffic.

Abstract: A method performed in an intrusion detection/prevention system, a system or a device for determining whether a transmission control protocol (TCP) segment in a TCP connection in a communication network is acceptable. The TCP connection can include TCP segments beginning with a three way handshake. A TCP segment can include a field for a timestamp. A timestamp policy of plural timestamp policies is identified, the timestamp policy corresponding to a target associated with the segments in a TCP connection. A baseline timestamp is identified based on a three way handshake in the TCP connection. Segments in the TCP connection are monitored. The segments in the TCP connection are filtered as indicated in the timestamp policy corresponding to the target, the timestamp policy indicating whether the segments are to be filtered out or forwarded to the target by comparing the timestamp of the segments to the baseline timestamp.

Abstract: Fragment trains in a communication network are analyzed. A fragment train includes fragments in the same fragment train and associated with the same target system. One or more fragment reassembly policies are identified out of several fragment reassembly policies, where the fragment reassembly policy corresponds to a target system associated with fragments in a fragment train. The data in the fragments in the fragment train are provided in an order indicated by the fragment reassembly policy. The fragment reassembly policy can include determining the order responsive to an offset and a more fragments indication in the fragments, and/or indicating an order specific to overlapped fragments such as comprehensively overlapped fragments.

Abstract: A method performed in an intrusion detection/prevention system, a system or a device for analyzing segments in a transmission in a communication network. The transmission includes segments in the same transmission control protocol (TCP) session. Segments in a transmission are monitored. Data in the segments in the transmission are reassembled in an order indicated by a segment reassembly policy, the segment reassembly policy indicating an order specific to at least comprehensively overlapped segments.

Abstract: In an intrusion detection/prevention system, network traffic is received and checked for a matching pattern. Upon identifying the matching pattern, the network traffic with the matching pattern is evaluated against rules that are represented by a rule tree. References to rule options are represented in the rule tree and are stored separately from the rule tree. The rule tree represents unique rules by unique paths from a root of the tree to the leaf nodes, and represents rule options as non-leaf nodes of the rule tree. Evaluating the network traffic includes processing, against the network traffic, the rule options in the rule tree beginning at the root. Processing of the rules represented by subtrees of nodes with rule options that do not match is eliminated. The network traffic is evaluated against rules terminating in leaf nodes only for combinations of rule options that match the network traffic.

Abstract: A method performed in an intrusion detection/prevention system, a system or a device for determining whether a transmission control protocol (TCP) segment in a TCP connection in a communication network is acceptable. The TCP connection can include TCP segments beginning with a three way handshake. A TCP segment can include a field for a timestamp. A timestamp policy of plural timestamp policies is identified, the timestamp policy corresponding to a target associated with the segments in a TCP connection. A baseline timestamp is identified based on a three way handshake in the TCP connection. Segments in the TCP connection are monitored. The segments in the TCP connection are filtered as indicated in the timestamp policy corresponding to the target, the timestamp policy indicating whether the segments are to be filtered out or forwarded to the target by comparing the timestamp of the segments to the baseline timestamp.

Abstract: Fragment trains in a communication network are analyzed. A fragment train includes fragments in the same fragment train and associated with the same target system. One or more fragment reassembly policies are identified out of several fragment reassembly policies, where the fragment reassembly policy corresponds to a target system associated with fragments in a fragment train. The data in the fragments in the fragment train are provided in an order indicated by the fragment reassembly policy. The fragment reassembly policy can include determining the order responsive to an offset and a more fragments indication in the fragments, and/or indicating an order specific to overlapped fragments such as comprehensively overlapped fragments.

Abstract: A method performed in an intrusion detection/prevention system, a system or a device for analyzing segments in a transmission in a communication network. The transmission includes segments in the same transmission control protocol (TCP) session. Segments in a transmission are monitored. Data in the segments in the transmission are reassembled in an order indicated by a segment reassembly policy, the segment reassembly policy indicating an order specific to at least comprehensively overlapped segments.