US Patent 11539718 Efficiently performing intrusion detection

Some embodiments of the invention provide a method for performing intrusion detection operations on a host computer. The method receives a data message sent by a machine executing on the host computer. For the data message's flow, the method identifies a set of one or more contextual attributes that are different than layers 2, 3 and 4 header values of the data message. The identified set of contextual attributes are provided to an intrusion detection system (IDS) engine that executes on the host computer to enforce several IDS rules. The IDS engine uses the identified set of contextual attributes to identify a subset of the IDS rules that are applicable to the received data message and that do not include all of the IDS rules enforced by the IDS engine. The IDS engine then examines the subset of IDS rules for the received data message to ascertain whether the data message is associated with a network intrusion activity. For instance, in some embodiments, the IDS engine identifies one rule in the identified subset of IDS rules as matching the received data message, and then processes this rule to determine whether the data message is associated with an intrusion.