The US National Security Agency (NSA) today issued a warning about a new wave of cyber attacks against e-mail servers. The attacks were carried out by one of Russia's most advanced spy units.
The NSA says members of Unit 74455 of the GRU Main Center for Special Technologies, part of Russia's military intelligence service, have attacked email servers running Exim mail transfer agent (MTA).
The team, also known as "Sandworm", has been attacking Exim servers since August 2019, taking advantage of a critical vulnerability (CVE-2019-10149), the NSA said in a security alert [PDF] announced today.
"When Sandworm exploits CVE-2019-10149, the victim's system downloads and runs a shell script from a controlled domain by Sandworm," the NSA said.
This shell script I will:
- Add privileged users
- Disable network security settings
- Update SSH settings to allow remote access
- Run an additional script to allow further exploits
The NSA now warns private and government agencies to update Exim servers to version 4.93 and look for signs of breach. Violations are listed in the PDF issued by the NSA.
The Sandworm team has been active since the mid-2000s and is believed to be the hacker team that developed the BlackEnergy malware that caused a blackout in Ukraine in December 2015. In December 2016, the team also developed the famous ransomware NotPetya which caused billions of dollars in losses to companies around the world.
Vulnerability CVE-2019-10149 was unveiled in June 2019 and has the code name "Return of the WIZard".
Within a week of its revelation, various hacking groups began using it. Two weeks later, Microsoft also issued a warning at the time, warning Azure customers.
Almost half of all Internet email servers run on Exim. According to statistics as of May 1, 2020, only half of these Exim servers have been updated to version 4.93 or later, leaving a large number of systems vulnerable to attack.