Denial-of-service (DDoS), SQL injection, and mobile attacks are among the top topics of discussion on hacker forums -- but they are far from the only topics, according to a study published today.

According to a study of a 220,000-member hacker forum conducted by data security vendor Imperva, the forum is used by hackers for training, communications, collaboration, recruitment, commerce, and even social interaction.

"Commercially, this forum serves as a marketplace for selling of stolen data and attack software," the study says. "The chat rooms are filled with technical subjects ranging from advice on attack planning to solicitations for help with specific campaigns. This forum is also a place where curious neophytes can find 'how-to-hack' tutorials."

Hacker discussions are spreading, the study says. Attack discussions on the forum have grown an average of 157 percent year-over-year between 2007 and 2010, the study says.

The most discussed topics in the forum during the past year were DDoS attacks, which accounted for 22 percent of discussions, followed by SQL injections, which comprised 19 percent. Mobile hacking saw very strong growth in the forum during the four-year study period, with iPhone hacking leading the way.

Twenty-five percent of forum discussions from June 2010 to June 2011 focused on "beginning" hacking, with members spending 6 percent of their time sharing "how-to" tutorials and discussing basic methodologies, the study says.

But not all of the discussion focused on hacking, according to Imperva. The study gives examples of hackers' conversations on topics ranging from religion to movies to acts of revenge.

Have a comment on this story? Please click "Comment" below. If you'd like to contact Dark Reading's editors directly, send us a message.