A personal firewall should protect your computer against external attacks by hackers or worms and against internal betrayal by spyware or Trojan horse programs. It shouldnt inundate you with alerts or otherwise interfere with normal computer use.
We tested new versions of two well-known firewalls in three distinct ways. On a direct, unprotected connection to the Internet, we ran a dozen Web-based tests to ensure that all ports were stealthed—completely hidden from the outside.
We ran 10 leak-test programs—single-purpose utilities that attempt to circumvent the firewall in the same way a worm or Trojan might. Finally, we took the gloves off and attacked the firewall process using techniques available to a malicious program.
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