A team of security researchers has engineered a way of hiding malware in sentences that read like English language spam. The research led by Dr. Josh Mason of Johns Hopkins University along with Dr. Sam Small of Johns Hopkins, Dr. Fabian Monrose of the University of North Carolina, and Greg MacManus of iSIGHT Partners outlined the threat in a paper English Shellcode (PDF) presented at the 2009 ACM Conference on Computer and Communications Security. According to the UK’s Computing, the paper shows hackers could evade anti-virus protection by hiding malicious code in sentences that read like English language spam
The article says that attackers could develop a tool that would be the next step in the hacking and virus arms race. Hackers could hide alphanumeric shellcode in valid files which would activate the malicious payload of a code-injection attack. This attack vector could give attackers control of system resources, applications, and data on a compromised computer.
The researchers report they can generate English shellcode in less than one hour on standard PC hardware. The text in bold is the instruction set and the plain text is skipped. “There is a major center of economic activity, such as Star Trek, including The Ed Sullivan Show. The former Soviet Union. International organization participation.”
The good news, Dr. Mason said that the widespread use of this attack vector is limited because the alphanumeric character set is much smaller than the set of characters available in Unicode and UTF-8 encodings. This means that the set of instructions available for composing alphanumeric shellcode is relatively small. “There was really not a lot to suggest it could be done because of the restricted instruction set,” said Dr. Mason. Long strings of mostly capital letters, for example, would be very suspicious.
Computing claims the work is a breakthrough. Current network security techniques work on the assumption that the code used in code-injection attacks, where it is delivered and run on victims’ computers, has a different structure to non-executable plain data, such as English prose. If an attacker challenge’s the assumption that executable code structure is different from non-executable data malware would be almost impossible to detect.
Dr. Nicolas T Courtois, an expert in security and cryptology at University College London, said malware deployed in this way would be “hard, if not impossible, to detect reliably.” The research is a proof of concept, but Dr. Mason doubts any hackers are using the technique to disguise their code. “I’d be astounded if anyone is using this method in the real world owing to the amount of engineering it took to pull off,” he said. “A lot of people didn’t think it could be done.”
Professor John Walker, managing director of forensics consultancy Secure-Bastion, argued the research highlights the flaws in the anti-virus community’s approach to security exploits. “There is no doubt in my mind that anti-virus software as we know it today has gone well past its sell-by date,” he said.
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If this technology gets out in the wild, most experts believe that the current signature-based anti-malware products will miss the attack and leave us all defenseless. Sounds like something the chip makers should be working on. Is this why Intel bought McAfee?
What do you think?
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Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.
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