Keanini of nCircle says that the best protection from malicious Web apps is also one of the most difficult safeguards to implement: educated users who are mindful of online security.

Rule number one is simple: If you have any doubt, don't click. This single rule would help people avoid most Web app malware, but it seems to be hard to drill into users' heads.

Given that an ill-advised click is almost inevitable, your next line of defense is to keep your security software up-to-date: Most such software can spot malicious behavior and can block many unknown threats as well, but the strongest protection comes from having updated security software that can identify current threats.

Malicious Web apps exploit vulnerabilities in your operating system or third-party applications to compromise your PC. You should enable Automatic Updates for Windows and other software that provides automatic up­­dating. Apply new updates as soon as they become available, in case exploit code is already circulating in the wild by the time the vendor develops a patch.