Attackers Crib Exploit Code, But Net Benefit For Defenders

The crime packs used by criminals to create malware campaigns to compromise and control victims' computers rarely use original attacks, instead relying on reusing techniques found in publicly released exploit code.

An analysis of 18 exploits used by the top 20 crime packs found that the crucial code used in each attack could be traced back to information released by a security researcher, a blog posted by a security firm describing the exploit, or a sophisticated attack created for an espionage campaign. The analysis, presented by Trail of Bits' CEO Dan Guido at last month's BruCon security conference, highlights the dangers that exploit code can pose in a software ecosystem that is slow to patch known vulnerabilities.

"There are pros and cons: The APT groups get by fine totally on their own, they create their own exploits totally in-house, and there is value from a defensive point of view to understanding how these exploits work and what their limitations are," Guido said. "On the other hand, when you see all these security researchers beating up on Java, you know that code is going to slot right into a space waiting for it."

In his analysis, Guido found that eight of the attacks included in the crime packs targeted Adobe Flash and Reader and Internet Explorer, but would only work on Windows XP. Half of the attacks targeted more modern platforms but relied on vulnerabilities in Oracle's Java software platform. Only a single attack, which targeted the Windows TrueType parsing vulnerability, could work on all Windows platforms at the time it was released. That exploit was publicly disclosed in 2011 in an analysis of the Duqu espionage Trojan.

For the most part, the exploits are unreliable and poorly written, he says.

"The only way that these crime packs seem to be able to get really good exploitation capabilities is if they are handed to them on a silver platter by some incredibly complicated and sophisticated APT group," Guido said during his BruCon presentation.

The situation is much different from half a decade ago when the authors of major exploit packs would compete on having unique exploits for certain vulnerabilities in their software, says HD Moore, chief research officer at Rapid7, a vulnerability management firm. Now, once an exploit is publicly discussed, everyone jumps on developing a version of the attacks, he says.

"They need exploits from somewhere, and they might as well use the ones that are available," Moore says. "There is no economic reason why they would go out of their way to build new exploits for what they are doing."

[Windows XP machines six times more likely to be infected by malware than newer versions of the OS, according to new Microsoft Security Intelligence Report (SIR). See Microsoft Software, Overall Operating System Vulnerability Disclosures Rise.]

The data suggests that quashing the publication of exploit code could have a positive effect on the security of the software ecosystem. Yet such approaches have already been tried and largely failed. While defenders have frequently sought to limit the access of criminals and bad actors to the tools needed to circumvent security measures -- such as lock picks and knowledge of safe construction -- software security will not likely benefit from such measures. Software vulnerabilities are often discovered independently, suggesting that silencing the disclosure of a vulnerability and how to exploit the flaw would merely allow a bad actor more time to use an attack, says Darren Meyer, senior security researcher at Veracode, an application security firm.

"It is really important for the disclosure, or even the release of code, to be a possibility," he says. "The legal restraint of that would be a very bad practice."

In addition, attackers' laziness can benefit defenders: The quick adoption of publicly available exploits by the creators of crime packs is also a weakness, says Brian Gorenc, manager of the Zero Day Initiative for HP Security Research.

"The key takeaway here is that a crime pack author’s strength is simultaneously one of its greatest weaknesses," he said in an e-mail interview. "This predictability can give enterprises a leg up on defending their networks."

During his presentation, Trail of Bits' Guido found that a relatively small number of tactics could eliminate much of the risks of crime packs. Companies that opt for more modern platforms are much safer, he says.

"You have all this incremental work going into updating minor versions of applications," he said. "But forget about that -- spend the time on updating to the next major version because then you get the new mitigations."

Eliminating the Java plug-in from the enterprise and using a different browser to access internal resources than is used to surf the Web can also remove known dangers, he said.

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