Some Ad Networks Are Bad News

By Larry Seltzer  |  Posted 2007-11-12

Some Ad Networks Are Bad News

You wouldnt go surfing to just any site. Youre 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 werent careful enough with their own security. When you trust a Web site you have to trust everyone its in bed with.

Follow the latest developments surrounding Google in Clint Boultons Google Watch blog.

The first one I became aware of was YNet, an Israeli news site. Dont go to that site just yet. The site I read is in English. The Hebrew site at 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, 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 cant 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.

Ive 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 its 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 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 ( that performed the redirect.

Next page: Take me out to the malware ...

Take me out to

the malware ...">

And Ynet isnt the only news site to be infected with this plague. Its 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 Ive confirmed that the attack is still on the site, although its not clear that that specific flash movie is actually being served on any customer sites.

The attack itself is interesting enough (yawn!), but Im 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 hasnt bothered yet to do anything about it, at least as far as I can tell.

In all of these news site cases, Ive seen the redirect performed through the same Flash movie mechanism, but I think the movie was served from three different sources:, and in the Tucson Newspapers site all of the ad content appears to be served from through Akamai. Ad networks have complicated relationships, but Im 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:, the site of Major League Baseball. Its not clear yet where the redirect is coming from, but it goes through, which hosts what seems to be the same malicious Flash movie, to and on to the fake anti-malware ad, which weve seen both at and

To read about why Googles DoubleClick deal is facing Senate scrutiny, click here.

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 wouldnt tell you to avoid any specific sites, except maybe

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 theres 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 Larry Seltzer has worked in and written about the computer industry since 1983.

Check out eWEEK.coms for the latest security news, reviews and analysis. And for insights on security coverage around the Web, take a look at Security Center Editor Larry Seltzers blog Cheap Hack

More from Larry Seltzer

Rocket Fuel