Random search strings in Google can yield sites hosting drive-by downloads of malicious content.
As the automated Mpack attack continues to turn thousands of legitimate Web sites into compromised sites offering drive-by downloads of malicious software, security researcher Roger Thompson over at Exploit Prevention Labs reminds us there are other exploits compromising legitimate sites, and some are as easy to find as entering a simple search string on Google. For more than a week (starting before the current Mpack attack), Thompson has been posting a list of dangerous search strings on his blog site. I've collected these and indicated in parentheses some of the known exploits associated.
Exploit Prevention Labs makes LinkScanner, a browser plug-in that will identify and block known exploits on tainted sites before you download the page. There are other safe surfing tools available as well; some are free.