INTERROGATING MALWARE

Identifying a behavior of a service is disclosed. A predetermined interrogation packet that corresponds to a hypothesis is sent to a network communication port of a receiver. The predetermined packet is one of a plurality of predetermined interrogation packets sent to the network communication port. The hypothesis is consistent with a behavior of a corresponding service. The predetermined interrogation packet invites an expected action. The expected action is detected. It is determined that the behavior of the service that corresponds to the hypothesis is operating.