Chinese state-run hackers have launched an extensive cyberespionage campaign, compromising hundreds of organizations by exploiting a zero-day vulnerability in a popular email security appliance, as revealed by Mandiant, a cyber threat intelligence firm.
Furthermore, this campaign is considered the most extensive Chinese cyber spying operation in years, with a “high confidence” judgment linking it to Beijing. The hackers targeted Barracuda Networks Email Security Gateway appliances, utilizing a remote command injection zero-day vulnerability that had been active since at least October.
Despite Barracuda Networks releasing a security patch on May 20, the company advised a subset of customers to replace their equipment immediately due to signs of ongoing infection even after applying the fix.
Approximately 5% of active ESG appliances worldwide have shown indicators of compromise, highlighting the persistence of the attackers. Mandiant, assigning the name UNC4841 to the campaign, found similarities in infrastructure and malware code with other Chinese threat actors, indicating a Chinese origin for the operation.
Mandiant warned that the hackers have the ability to move laterally within compromised networks, emphasizing the need for continued vigilance. The targets of the campaign included a ministry of foreign affairs in a Southeast Asian country, as well as foreign trade offices and academic research organizations in Taiwan and Hong Kong.
Hackers sought email accounts belonging to officials involved in high-level diplomatic meetings. The initial access was gained through emails containing generic subject lines and body lures, designed to bypass spam filters and discourage thorough investigations.
The hackers exploited a vulnerability by injecting it into the filename of malicious .tar attachments, triggering the attack. Mandiant and Barracuda identified three primary backdoors used by the hackers, named SeaSpy, Saltwater, and Seaside.
In response to the patch released by Barracuda, the Chinese hackers modified SeaSpy and deployed it with new file names, indicating their ability to adapt and change tactics in real time. As defenders strive to counter their actions, UNC4841 is expected to continue evolving its methods to evade detection.
