Some Ad Networks Are Bad News

By Larry Seltzer - eWEEK

You wouldn't go surfing to just any site. You're careful about where you go. You only go to sites you trust.

But who are you trusting? A series of recent attacks has resulted in seemingly respectable news sites serving malware and redirecting users to sites that serve malware.

The problem is in the ads on those news sites. The ads are served by advertising networks that weren't careful enough with their own security. When you trust a Web site you have to trust everyone it's in bed with.

The first one I became aware of was YNet, an Israeli news site. Don't go to that site just yet. The Ynetnews.com site I read is in English. The Hebrew site at ynet.co.il is far more popular, in fact the most popular news site in Israel. It is the Internet site for Yedioth Ahronoth, a very large Israeli newspaper.

About two weeks ago I noticed that after going to the page from a bookmark that had only the domain name in it I was redirected to a different site on the domain malware-scan.com, a classic "rogue anti-spyware" site that I recognized from prior experience. There are a variety of scams that come from this domain, but this one said that my system was infected with malware and that they could scan it. The browser window shrinks down to dialog box size to give the appearance of a dialog box. You can't cancel out; no matter what you do (other than killing the process in Task Manager) you are brought to the "scanning" Web site, where your system is faux-scanned, and lots of malware is found on it.

I've observed this attack many times now, both through up-to-date versions of Internet Explorer and Firefox. Sometimes the "app" being pushed is a "performance optimizer" rather than a malware scanner, but in any event it's malware. Kaspersky Antivirus on my system recognized it as "not-virus.Hoax.Win32.Renos.kd." I got a lot of analysis help from the ubiquitous Gadi Evron, from independent analyst Thor Larholm and from Adam Thomas of Sunbelt Software.

The redirect came from code in one of the many ad sections in the Ynetnews.com home page. The code in this page is disturbingly complex and contains a large number of IFRAME tags, many to other domains. An IFRAME tells the browser to go to some other site and read in the HTML from there. This is an example of what is called transitive trust: I trusted Ynet, it trusted its ad providers, therefore I trusted those ad providers. Big mistake. The attack is still up and running as of Sunday, Nov. 11. Incidentally, the actual attack came through Flash code on one of the ad domains (adtraff.com) that performed the redirect.

And Ynet isn't the only news site to be infected with this plague. It's spreading. Tucson Newspapers had a similar attack. That attack, according to a report, was on the site for 10 to 18 days. They say, "Our people reacted very quickly," which seems to be a contradiction.

A third attack, on the Boston Herald, was reported to have come in through a Flash ad on advertising.com. I've confirmed that the attack is still on the advertising.com site, although it's not clear that that specific flash movie is actually being served on any advertising.com customer sites.

The malware-scan.com attack itself is interesting enough (yawn!), but I'm basically interested in how legitimate news organizations got to include such obviously undesirable content on their sites. Not only does the attack itself subject the user to malware, but it takes them away from the news site. And yet Ynet hasn't bothered yet to do anything about it, at least as far as I can tell.

In all of these news site cases, I've seen the redirect performed through the same Flash movie mechanism, but I think the movie was served from three different sources: advertising.com, adtraff.com and in the Tucson Newspapers site all of the ad content appears to be served from tucson.com through Akamai. Ad networks have complicated relationships, but I'm definitely confused. Someone is selling this dirty ad, and legitimate sites are getting scammed.

And then, just as I was finishing up this column, we found another one on an even more significant site: MLB.com, the site of Major League Baseball. It's not clear yet where the redirect is coming from, but it goes through newbieguide.com, which hosts what seems to be the same malicious Flash movie, to adverdaemon.com and on to the fake anti-malware ad, which we've seen both at longlifepc.com and fixthemnow.com.

BTW, yes, of course even eWEEK has ads from outside ad networks such as DoubleClick, recently bought by Google. Is this a risk? At some level yes, of course it is. Both DoubleClick and eWEEK have no history of problems in this regard that I can recall, and I wouldn't tell you to avoid any specific sites, except maybe YNetnews.com.

The point is that Web sites that have content relationships with outside sites need to scrutinize the content coming from those sites. They need accountability from those partners, and they need contingency plans for taking the content down in case there's a problem with it. And someone needs to investigate these malware ad attacks further to find out how legitimate sites can avoid them.

Security Center Editor eWEEK.com's Security Center for the latest security news, reviews and analysis. And for insights on security coverage around the Web, take a look at eWEEK.com Security Center Editor Larry Seltzer's blog Cheap Hack