Taken from PCWorld Magazine, May 2012 Edition

Web Apps are great. The’re available for use virtually anyway, anytime, from practically any device that has a Web browser. Web apps are also easy to update and maintain: The developer tweaks the app on the Web server, and everyone who uses it has access to the latest version.  But Web apps can contain more than you bargained for, and in some instances they may actually be malicious. You need to be aware of the risks that Web apps can pose, and know how to protect yourself.

A Web app is essentially a full-fledged application that runs within your Web browser. Just as easily as a Web app can track your reminders or play a game, it can infect your PC. While they allow increased functionality within the browser, users should be aware of how deeply into your system they may be able to reach.  Some malware attacks try to entice you to click a link in an email message, which them connects to a malicious Web app that infects your PC with malware.

The best protection from malicious Web apps is also one of the most difficult safeguards to implement.  Rule number one is simple… If you have any doubt, don’t click.  Given that an ill-advised click is almost inevitable, your next line of defense is to keep your security software up-to-date.   Malicious Web apps can exploit vulnerabilities Windows and other software as well, so you should make sure your operating system and all your software are updated.