Leak tests are small, non-destructive, programs designed by security experts that deliberately attempt to bypass a firewall's outgoing security measures. The rationale behind them is painfully simple: "If this test can get past your computer's security defenses, then so can a hacker." Explicitly designed to help identify a firewall's security flaws, leak tests provide the invaluable function of informing the user whether or not their firewall is providing adequate protection. The tests pose no real threat to the security of a computer as they are harmless simulations of the attack techniques typically used by spyware and Trojan horse programs. There are many leak-testing programs available - each one designed to exploit a particular flaw and each using a particular attack technique to break a firewall's standard protection mechanisms.