In the modern social Web era, users are often encouraged to leave comments on articles and blog posts, yet not all comments are the same. A class of comments, known as "comment spam," could lead to user and site exploitation.
A new report from security firm Imperva, lays bare how comment spam is constructed and executed. In contrast to a regular comment, the purpose of comment spam is to embed a link or an unsolicited advertisement.
One of the primary purposes of comment spam isn't to directly exploit a user, but rather to help improve search engine optimization (SEO) for the spammer. By having more backlinks from Websites, the theory is that a given site will be able to improve its SEO positioning.
Imperva found that 80 percent of all comment spam traffic is generated by only 28 percent of the attackers.
"Seeing that a minority of attackers actually generate the majority of the comment spam demonstrated that we could profile the behavior of a comment spammer and then take action," Barry Shteiman, director of security strategy at Imperva, told eWEEK.
By understanding who the comment spammer is, it is possible to block the offending comments by IP address location and reputation. The report also found a high degree of automation is present in comment spam operations.
Once a spammer is successful in planting comment spam on a site, there is usually a spiked increase in the comment spam traffic, Shteiman said. "Some of the more automated comment spam tools may gather a successful attack on a Website and add that Website to their list of spammable sites so others could use it too," he explained.
Comment spammers use a number of tools to automate their activities. One of them is the G-Lock Blog Finder for helping locate and identify blogs to comment on. There are also automated tools such as Comment Blaster for writing the actual comments used.
Many sites employ comment-verification tools, including captcha verification for telling computers and humans apart. The Imperva report notes that the comment spammers have tools to deal with captcha challenges, as well.
Comment spamming tools like ScrapeBox and Gscraper provide a comprehensive set of features to locate, place and monitor comments.
Comment spam is a serious business problem that is trending fast, Shteiman said. "A good and unfortunate example could be seen on really big community Websites such as YouTube," Shteiman said. "Comment spam is such a major problem to them that they decided to require a Google account log-in from users in order to post comments."
YouTube found that the hassle of authenticating users—and potentially having fewer comments because of that—is essential for dealing with comment spam.
Although comment spam isn't necessarily a direct path to a user being exploited, it does expose a number of risks.
"If a Website is vulnerable to comment spam, which essentially is some text and a link, how long [will it be] before attackers start linking to malware and use major sites for waterhole attacks using the comment spam vector?" Shteiman said. "In fact, there have already been instances of these attacks in the past."
Sean Michael Kerner is a senior editor at eWEEK and InternetNews.com. Follow him on Twitter @TechJournalist.