If you haven't patched that media player or web browser in a while, now might be a good time. MySpace, Excite and Blick have been caught serving banner ads that attempt to install malware on machines running unpatched software.

People who visit MySpace chat forums using out-of-date web browsers and media player plugins such as Macromedia Flash and QuickTime are being treated to drive-by downloads that install a plethora of nastyware on their machines, according to this article on Security Fix. The entries, which include Virtumonde, WinFixer and ClickSpring, come courtesy of banner ads hosted on the social networking site.

Not to be outdone, Excite and German language site Blick.ch are also serving malicious banner ads, according to entries here and here from Sandi Hardmeier, a Microsoft MVP who blogs about security.

The incidents are the latest example of the crud that all too often makes its way onto end users machines via the servers owned by ad networks such as DoubleClick and Real Media. Cyber criminals typically create sham companies that pose as legitimate advertisers and then slip malicious code into their banner ads. The networks work hard to snuff out the tainted banners, but sometimes fail.

If three sites have been caught offering malware-laced banner ads, chances are good that other destinations are doing the same. Savvy readers should make sure all applications on their machines are up to date. One easy way to check is by using Secunia's Software Inspector. Of course, running the NoScript extension with the Firefox browser also offers protection against many malicious banner ads. ®