Any company that does business online knows the importance of mastering search engine optimisation (SEO) techniques to get their content atop the Google rankings. It turns out malware pushers care about SEO, too, and at DefCon later this week researchers will show just how big a deal it has become.

The full findings won't be released until mid-week, but CSO got a preview in an interview Friday with Paul Judge, chief research officer and VP of cloud services for Barracuda Networks, and Dave Maynor, research scientist with Barracuda Labs and CTO-cofounder Errata Security.

The findings are based on a five-month study in which Barracuda Labs observed and measured attackers' use of search engine results to host malware or redirect users to malicious sites. Data was collected several times a day and checked for malicious content across Google, Yahoo!, Bing and Twitter.

"We realised that attackers are trying to get in front of as many eyes as possible. They take advantage of popular search terms and we wanted to see exactly what they're doing," Judge said. "We set the system crawlers to look at Google, Yahoo! and Twitter, figure out the popular search terms, then we searched for those pages and analysed them in search of malicious content."

In total they reviewed 8,000 search terms and 5 million search results. Not surprisingly, Maynor said, "Google is pretty full of malware." In fact, 68 percent of the malware found was on Google. To Judge's surprise, only one percent of it was found on Twitter. Yahoo! Accounted for 18 percent of the malware found.

Like Microsoft in the first part of the last decade, Google is a major target these days because it accounts for so much online market share, Judge said. Though Twitter's growth has exploded in the last couple years, it isn't focused on search rankings as Google is.

The researchers also studied the times of day and days of the week where malicious activity was strongest. The period between 1 and 5 a.m. represented more than half the malware generated. Maynor said the working theory is that hackers in Europe are up and about at that time. Meanwhile, Mondays have turned out to be the busiest day of the week, accounting for about one third of malicious activity.

"People get back to their office on Monday and they don't feel like working yet, so they visit other sites and that's when they fall in the trap," Maynor said.

Maynor will present the findings at 11am Saturday at the Riviera Hotel and Casino.