These are sites that distribute, promote or provide hacking tools and information to help others gain unauthorized access to computer systems and computerized communication systems. These sites offer instructions on illegal or questionable tactics, such as creating viruses, distributing cracked or pirated software, or distributing other protected intellectual property. The number of sites in this category grew by approximately 30 percent in 2009 and, by their very nature, should be considered suspicious. While there are several sites in this category with relatively admirable codes of ethics, those tend to be the exception. In addition to information, many sites provide services that are easily leveraged for malware hosting.
Malware has to live somewhere. And while some Web filtering solutions can detect known malware hosts, most malware hides in sites that are otherwise benign. According to a report from Blue Coat Systems, the five most commonly compromised Web sites range from online storage to -- surprise -- adult content. Click through this slideshow for more information.