A recurring theme in the IT security world is that a firewall can only be as effective as the policy that it is enforcing. To that end Total Immersion Security That's because for these advanced attacks to work, the bad guys need to find only one vulnerability in order to sneak their malicious software onto the target network. Once they get a foothold, they can break into other computers, steal data, and then move it offshore. The good guys have to be perfect -- or at least very quick about spotting intrusions -- to keep APT threats at bay.