Just to make everybody a little bit paranoid, I found the following article in EWeek about viruses being delivered via Banner Ad Servers:
IE Exploit Targets Banner Ad Servers
By Ryan Naraine
November 22, 2004
The ubiquitous banner ad has become the latest delivery mechanism for exploit code targeting a known flaw in Microsoft Corp.'s Internet Explorer browser.
During a 12-hour window over the weekend, hackers broke into a load balancing server that handles ad deliveries for Germany's Falk eSolutions and successfully loaded exploit code on banner advertising served on hundreds of Web sites.
"Users visiting Web sites that carry banner advertising delivered by our system were periodically delivered a file from the compromised site. This file tries to execute the IE-Exploit function on the users' computer," Falk eSolutions confirmed Monday.
The exploit (Bofra/IFrame) takes advantage of an IE vulnerability discovered and reported to Microsoft earlier this month. It is a variant of the MyDoom virus that launched zero-day attacks on vulnerable IE users two weeks ago.
The flaw, which does not affect IE users running Windows XP Service Pack 2 (SP2), has not yet been patched.
The SANS Internet Storm Center (ISC), which tracks malicious Internet activity, said it was in the process of contacting other Falk customers in Sweden and the Netherlands that may have also been compromised.
SANS ISC Director Marcus Sachs told eWEEK.com the fact that the ad servers were used to distribute the exploit suggests that hundreds of sites, and possibly millions of users, were affected.
Sachs said the Center is highly recommending that users ditch the affected IE browser until Microsoft issues a fix.
"This is a strong candidate for an out-of-cycle Microsoft patch. There are real exploits circulating with real security risks," Sachs said, noting that the next scheduled patch from Microsoft won't be available until Dec. 14.
"The fact that this has already been fixed in SP2 suggests that Microsoft has been aware of it for a very long time," Sachs said, noting it was also very possible that the vulnerability was fixed during the SP2 code rewrite.
The ISC is urging Web site operators that serve banner ads to verify the banners do not contain the IFrame exploit code. "Or you might want to consider disabling banner ads for a little while to minimize the risk of accidentally infecting your users and propagating," the Center said.
Because the vulnerability is easy to exploit, Sachs said it is very likely that malware for this issue will emerge in many flavors and colors. In addition to the possibility of becoming infected while surfing a Web site, there are e-mail propagation vectors, he added.
NOTEThe full article is found at
http://www.eweek.com/article2/0,1759,1730904,00.asp