Russian Threat Group May Have Devised a 'Man-on-the-Side' Attack

Iron Liberty, a Russia-based cyber espionage group known for targeting energy, nuclear, and defense organizations worldwide, may have developed a dangerous new technique called a "man-on-the side" attack.

Secureworks warned about the new threat in a report this week describing a "man-on-the-side" (MOTS) attack to install malware. The security firm says MOTS differs from a typical man-in the-middle (MITM) attack.

"The difference between MITM and MOTS is straightforward," says Don Smith, senior director of the Counter Threat Unit at Secureworks. "With MITM, the attacker is present on infrastructure the traffic is traversing and can tamper with it," he says. "With MOTS, the attacker has sufficient access to observe and inject traffic which through timing/bandwidth is consumed by the victim before the legitimate reply arrives."

The security vendor's theory is based on its analysis of a campaign last year where Iron Liberty actors managed to install a malware tool called Karagany on a target system without leaving any trace of how they did it. According to Secureworks, its research showed no evidence of a phishing email, drive-by-download, or a malicious link being used to drop the malware on the system.

Secureworks' forensic analysis showed that Karagany was installed on the system shortly after its user initiated a legitimate request to download Adobe Flash over HTTP from Adobe's official website. Logs showed that Karagany was installed on the system in the short period of time during when the user request was initiated and the Adobe file was downloaded.

Secureworks found that Kargany files were dropped on the system just 20 seconds after the initial Flash Player binary was downloaded, and by 27 seconds, additional malicious files were downloaded on the system.

Multiple Explanations

"There are several credible explanations for how the Karagany payload was delivered alongside the Adobe installer file," Secureworks said in its report. But none of them appeared very likely in this case, the company said.

For example, the malware could have been downloaded if Adobe's website had been compromised. But Secureworks' investigation showed no indication that such a thing had happened during the compromise timeframe.

Another possibility was that someone with access to the victim organization's internal or gateway systems had intercepted and manipulated traffic between Adobe and the infected system in a typical MITM attack. Here again, Secureworks was unable to find any signs that such activity had taken place. A third possibility, which Secureworks similarly deemed unlikely, was a Border Gateway Protocol (BGP) attack where the user's traffic was routed through attacker-controlled systems.

Instead, they believe the Iron Liberty actors likely managed to compromise a router outside the victim organization, and then used it to intercept the Adobe installer request and return a Trojanized response, Secureworks said.

"Being 100% clear, the traffic injection we saw in these cases could have come from Man on the Side or from Man in the Middle," Smith says. "We do not know how the fraudulent traffic was injected. [It] could have been router compromise or could have been traffic injection."

For enterprises, attacks like these are another reason not to implicitly trust anything on the Internet. Protecting against a man-on-the side attack is no different from dealing with a man-in-the-middle attack, Smith says.

Some common mitigating tactics include using SSL encryption and checking the hashes of files that are downloaded from the Internet to make sure they match with the original file.

With a man-on-the-side attack, there are two parties trying to respond to the same request and the bad actor's goal is to get in first, Smith says.

The only way to detect such activity would be to monitor the sequence of packets arriving in response to a request and looking for out of sequence packets arriving and likely being discarded. "You need to be extremely well instrumented to detect it," Smith says.

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