Anti-virus Software: The Next Big Worm Target?

News Analysis: Security researchers warn that easy-to-exploit code execution flaws in several popular anti-virus products could lead to a devastating worm attack.

Finnish anti-virus specialist F-Secure Corp. has pushed out patches for multiple code execution vulnerabilities in its security software suite, prompting a new round of warnings that flaws in security products present a lucrative target for malicious hackers.

The updates from F-Secure, rated "highly critical" because the vulnerabilities put users at risk of security bypass and system access attacks, come just weeks after rival Symantec Corp. publicly acknowledged that a high-risk buffer overflow in its AntiVirus Library could allow the execution of malicious code.

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Even more worrisome, the private researcher who discovered and reported the F-Secure vulnerabilities said several unnamed anti-virus vendors are also shipping products with the same security flaw.

"[F-Secure is] the first to actually publish a real advisory," said Thierry Zoller, a penetration tester based in Luxembourg. He said some companies fixed the bugs silently or put a small notice in a change log, and hinted strongly that there are many anti-virus engines still vulnerable.

"I will however not publish more details about the findings as of yet, there are too many AV engines vulnerable and I am going to wait until most of them have patched the flaws until I exactly disclose my findings," he said in note posted online.

Citing responsible disclosure constraints, Zoller declined to identify the companies with unpatched products.

Over the last 12 months, some of the biggest names in the anti-virus business have shipped critical software updates to cover code execution holes, and industry watchers say its only a matter of time before a malicious hacker is motivated to create a devastating network worm using anti-virus product flaws as the attack vector.

"The big surprise is we havent seen one yet," said Johannes Ullrich, chief technology officer at the SANS ISC (Internet Storm Center), a group of volunteers that track malicious activity on the Internet. "Thats the software thats exposed to malware and should be providing the first line of defense [from worm attacks]. Its sitting on every desktop and is really the perfect target," Ullrich said in an interview with eWEEK.

In its most recent annual report on the Top 20 vulnerabilities, the SANS institute warned that an increase in the number of flaws in client-side applications—including anti-virus and backup software—is giving attackers easy access to sensitive systems, including government and military networks.

Alex Wheeler, an independent security researcher who specializes in auditing security software, maintains a list of remote heap overflows found in products sold by Symantec, Panda Software Inc., Kaspersky Lab and Sophos Inc.

Wheeler blamed the bulk of the bugs on poor coding techniques and also pointed to an alarming tendency among anti-virus vendors to avoid fixing the actual flaws by using "heuristics" exploit detection.

"[They] fix a bug in their code by trying to detect exploits with their own product, which of course still contains the bug," Wheeler said in an e-mail exchange with eWEEK.

In some cases and with some vendors, Wheeler said, its a "pain" to handle the disclosure process. "[In one case], we kept telling them they had to patch their code, but they refused. We didnt really want to send them an exploit showing them how they could be 0wned, but thats what it came down to. They ended up fixing their code."

/zimages/3/28571.gifClick here to read about Symantecs troubles over the Norton AntiVirus "rootkit."

Marc Maiffret, chief hacking officer and co-founder at eEye Digital Security, said he believes anti-virus product flaws could lead to the first big non-Microsoft worm. "One of these days, I really think that someone will be motivated to create a really nasty exploit against one of these file decoding overflows, and it could be just as devastating as any automated worm attack," Maiffret said.

Maiffret said the hard-nosed competition in the anti-virus business has pushed companies to put marketing ahead of security concerns. "If you are in the security industry, you have a responsibility to keep your own products secure. In the last two years, weve seen a steady increase in these flaws, and theyre really easy to exploit," he said.

"When you think about it, its really the perfect attack vector for some kind of worm or automated malicious code. The vulnerabilities affect both gateway and desktop products, which makes it easy for a virus to spread."

"Its not a matter of whether its technically possible to write a worm today for anti-virus flaws. It depends on whether someone wants to do it. I personally believe its already happening on a very small, targeted scale where individual companies are being compromised and no one knows or will ever know. That, to me, is even more dangerous than the big disruptive network worms."

Maiffret cited the stealth attack against the University of Connecticut last year, in which hackers avoided detection for two years after placing a rootkit on a server that contained names, social security numbers, dates of birth, phone numbers and addresses for most of the universitys 72,000 students, staff and faculty.

"If theres an anti-virus flaw in a software on a business desktop, that makes that company a target. I can send a single malformed file through e-mail, targeting a specific user. and I can take control of that machine. Thats the kind of attack that avoids publicity and avoids detection," Maiffret said.

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