The AVG LinkScanner scans search results on Google, Yahoo!, and Microsoft's Live Search. And unlike similar technology from ScanSafe, it doesn't mask the user's IP address.
"In order to detect the really tricky - and by association, the most important - malicious content, we need to look just like a browser driven by a human being," Thompson told us. According to Thompson, nearly all web exploit toolkits track IP addresses, and they won't serve the same exploit twice to the same address.
Thus, when a scan turns up in a web site's log file, it looks an awful lot like a legitimate user visit. Thompson points out that AVG only scans the first page of results on sites like Google - unless the user clicks on subsequent pages. But clearly, with 20 million web surfers on board, even this is enough to wreak havoc with sites that so often pop to the top of the leading search engines.
In the discussion forums at Webmaster World, site gurus have pinpointed a specific user agent that betrays the anti-malware tool: "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;1813)." Hoping to fix their traffic numbers, they're filtering this agent from their log files. And at least one webmaster is serving up a dummy file each time the agent turns up. That way, he burns less bandwidth.
"I prefer to feed the same dummy file to most robotic tools," says the web master of TheSilhouettes.org. "There are thousands of them crawling around out there and they have voracious appetites. Only a handful are of any benefit to me, the rest are a nuisance and many are actually malicious."
Of course, this is the last thing Roger Thompson wants. He acknowledged that an AVG scan can be identified with that user agent. But he indicated this may change.
He also said AVG is interested developing some other solution to webmasters' problems - but this will take a back seat to security. "Our primary responsibility is to provide the best possible protection for our users, but we can and will seek a programmatic solution," he said. "Given that we've only just been alerted to this situation, we're still researching it, and it's not clear what we'll do at this point."
If AVG does mask its user agent - and fails to provide another workaround - its ghost traffic looks exactly like real traffic. And then the web is in trouble. After all, 50 million AVG users have yet to upgrade.
The Reg has always believed in log file analysis. Alternative methods from companies like Comscore and Nielsen seem to underestimate traffic from those who surf on their daytime work machines. Plus, Comscore's software gives us the the willies.
We always make an effort to filter robotic clicks from our files. And we use an outside organization, ABCe, to audit our numbers. But if AVG kills that user agent, even ABCe is powerless.
When we contacted ABCe, it was unaware of the problem too, and though it now acknowledges the issue, it's still mulling the solution. "[The AVG Linkscanner] can cause noticeable spikes in traffic levels logged by [a] site," reads its canned statement. "[We] will continue to review this and other technical areas."
And this is separate from the bandwidth problem. Extra bandwidth costs are negligible to The Reg. But as Adam Beale points out, this is a serious burden to smaller sites - and the AVG scanner is certainly hitting smaller sites.
We can't help but think there's a showdown on the way. ®