A security analyzer tests the security of a device by attacking the device and observing the device's response. Attacking the device includes sending one or more messages to the device. A message can be generated by the security analyzer or generated independently of the security analyzer. The security analyzer uses various methods to identify a particular attack that causes a device to fail or otherwise alter its behavior. Monitoring includes analyzing data (other than messages) output from the device in response to an attack. Packet processing analysis includes analyzing one or more messages generated by the device in response to an attack. Instrumentation includes establishing a baseline snapshot of the device's state when it is operating normally and then attacking the device in multiple ways while obtaining snapshots periodically during the attacks.