Most social networks will allow the posting of URLs and advertisements that might be infected with malware, according to a report published today.

In their new "Q4 Malware Update," researchers at anti-malware firm Dasient outlined the results of experiments conducted on 12 social networks to show their vulnerability to malware infection. The results: Social network users could be one click away from infection via malicious URLs or advertisements.

"Social networks have some work to do on their malware countermeasures," says Neil Daswani, CTO and co-founder of Dasient.

In one set of experiments, Dasient created "test" accounts on social media sites that were not connected to any real users and posted status messages on them. The status posts included links to benign URLs that were flagged as potentially malicious by Google's Safe Browsing lists or included links to a benign drive-by-download.

In the experiment, 81 percent of the social networking sites allowed the posting of URLs that were flagged on Google's Safe Browsing list, and all of them allowed the posting of URLs that contained the benign drive-by-download, Dasient says. Experiments on shortened URLs yielded similar results.

"Double-digit percentages of status messages on social networking sites have links in them, but most social networking sites don't scan the links for malware," Dasient says.

In a second set of experiments, Dasient posted advertisements on social networks whose click-through URLs led to a benign drive-by-download. When the "Click for a security test" link in the malicious-looking ad is clicked on, users are redirected to an ad landing page with a benign drive-by-download.

The social networks took a long time to disapprove the ads and take them down, according to Dasient. In one experiment, "the ad ran for over three weeks -- almost the fully allotted duration -- before the ad was disapproved," the report says.

"The ad received 159,767 impressions and 103 clicks. If we had put a more compelling picture on the ad [and] wrote much more enticing text ... our guess is that it probably would have received many more click-throughs."

Social networks need to step up their defenses, Dasient says. "We recommend that social networking sites should take advantage of resources such as Google's Safe Browsing API to check links against known blacklists, and scan links for Web malware threats so that their networks can be safer places for users over the medium and long-term."

The report also offered a look at current malware trends. "Malvertising is on a significant rise, having doubled from Q3 to Q4 2010," the report says. "Based on our Q4 estimates, three million malvertising impressions were served per day, an increase of 100 percent" over the year before, as compared to 1.5 million malvertising impressions

More than 1 million websites were estimated to be infected in Q4 2010, according to Dasient. The probability that an average Internet user will hit an infected page after three months of Web browsing is 95 percent, the report says.

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