Researchers at Sophos discovered the attack while inspecting infected Linux and Windows EC2-based cloud infrastructure servers running in Amazon Web Services (AWS). The attack, which Sophos says is likely the handiwork of a nation-state, uses a rootkit that not only gave the attackers remote control of the servers but also provided a conduit for the malware to communicate with their command-and-control servers. According to Sophos, the rootkit also could allow the C2 servers to remotely control servers physically located in the organization as well.
“The firewall policy was not negligent, but it could have been better,” said Chet Wisniewski, principal research scientist at Sophos. The attackers masked their activity by hiding it in HTTP and HTTPS traffic. “The malware was sophisticated enough that it would be hard to detect even with a tight security policy” in the AWS firewall, he said. “It was a wolf in sheep’s clothing … blending in with existing traffic.”
Sophos declined to reveal the victim organization, but said the attack appears to be a campaign to reach ultimate targets via the supply chain – with this as just one of the victims. Just who is behind the attack is unclear, but the RAT is based on source code of the Gh0st RAT, a tool associated with Chinese nation-state attackers. Sophos also found some debug messages in Chinese.
The attackers appear to reuse the same RAT for both the Linux and Windows servers. “We only observed the Linux RAT talking to one server and the Windows talking to a different control server, so we’re not sure if it’s even the same infrastructure,” Wisniewski said. The C2 has been taken down, he noted.
Just how the attackers initially hacked into the victim’s network is unclear, but Sophos suggests one possibility is that the attackers infiltrated a server via SSH. They also don’t have a lot of intel on the rootkit, such as which port it abused, nor do they know for sure what they were after. “It’s likely a supply chain attack, targeting this organization to get all of their downstream” clients or customers.
One of the rare aspects of the attack: it targeted Linux with a rootkit, which was called Snoopy. “They dropped the driver part of the rootkit, and called it Snoopy. Had it been called a legitimate file name on the Linux box, we probably wouldn’t have noticed it,”
It’s just a matter of time before the cloud become an active prey.