Online gaming is huge. It's also dangerous.

According to a June 2010 Nielsen NetView survey on Internet usage, online gaming has overtaken e-mail in terms of the total percentage of time Americans spend online (10.2 percent versus 8.3 percent). Only social networking scores higher, with a whopping 22.7 percent. Online gaming now consumes a staggering 407 million hours of U.S. citizens' time per year, according to Nielsen.

Nielsen's not the only one that noticed this trend; cybercriminals have taken note and are taking advantage of it, too, infecting games sites—from legitimate forums and tutorial sites to shadier download sites—to attack the unwary.

"As the gaming industry continues to grow, hackers will inevitably develop more ways to target this massive group," said Ondrej Vlcek, chief technical officer of Czech security company Avast, makers of avast! Internet Security 5.0 and avast! Free Antivirus. Avast continually gathers data about infected sites, publishing a monthly Most Wanted List to highlight the worst sites in a given portion of the Web. For October, Avast has sliced its data to reveal the riskiest gaming sites on the Web, to warn customers and raise awareness of the threat. Avast's worst offenders, as of October 6, 2010:

• Gamesfactoryinteractive.com
• Games-digest.com
• Mariogamesplay.com
• Anywhere-games.com
• Galacticflashgames.com
• Towerofdefense.com
 

To safely game online, Avast recommends a few simple precautions.

• Keep all your apps, and especially your antivirus, updated.
• Don't turn off your antivirus while you're playing games.
• Instead, use your antivirus' gaming function if you want to game uninterrupted.
• Beware of downloading games via warez sites, which are a known avenue for spreading malware.