Web Security ZoneAlarm Pro Firewall Gets Down to Business Symantec Targets Enterprise With Desktop Firewall Product Finder PC World's advice on what to buy, plus prices and specs on thousands of products . Instant Alerts Get email Alerts on stories that match your interest. To choose a keyword, click here. Choose the right expert at the right price, anytime day or night, at PC World Expert Help .
New updates fix a potentially disastrous flaw.
Several personal firewall vendors have released updates addressing your vulnerability to intruders who get in when you unsuspectingly run a malicious application that masquerades as a friendly one. The problem garnered public attention thanks to PC security guru Steve Gibson, whose Gibson Research Web site is best known for ShieldsUp, a test designed to expose a firewall's vulnerability to external attacks. Antivirus software can alert you to known Trojan horses, but if a new one gets through, your firewall is supposed to provide a second line of defense. Unfortunately, most personal firewalls failed LeakTest when it was released in December. All firewalls are meant to block unauthorized attempts to access a PC from the outside.