Chinese Lotus Blossom APT targets multiple sectors with Sagerunex backdoor
March 06, 2025
China-linked Lotus Blossom APT targets governments and industries in Asian countries with new Sagerunex backdoor variants.
Talos researchers linked China-backed Lotus Blossom APT (also known as Elise and Esile) to multiple campaigns targeting organizations in sectors such as government, manufacturing, telecommunications and media with the Sagerunex backdoor. The victims of the attacks are in the Philippines, Vietnam, Hong Kong and Taiwan.
The cyber espionage group has been active since at least 2012 and has been using the Sagerunex backdoor since at least 2016.
Talos observed the APT group using two new Sagerunex backdoor variants in attacks against telecom, media, government, and manufacturing sectors. These variants use cloud services like Dropbox, Twitter, and Zimbra for C2, replacing the original VPS method.
The variants are designed to gather, encrypt, and exfiltrate target host information to a remote server controlled by the attacker. The Dropbox and X versions were used between 2018 and 2022, while the Zimbra version has been active since 2019.
Detailed malware analysis reveals configuration and potential host paths.
“Our investigation uncovered two new variants of the Sagerunex backdoor, which were detected during attacks on telecommunications and media companies, as well as many Sagerunex variants persistent in the government and manufacturing industries.” reads the report published by Talos. “These new variants no longer rely on the original Virtual Private Server (VPS) for their C2 servers. Instead, they use third-party cloud services such as Dropbox, Twitter, and the Zimbra open-source webmail service as C2 tunnels to evade detection. In our malware analysis section, we will delve into the technical specifics of each Sagerunex backdoor variant and illustrate their configurations. Some configurations reveal the possible original file paths of the malware, providing insights into the threat actor’s host paths. ”
Talos attributes recent campaigns to the Lotus Blossom group based on the use of the Sagerunex backdoor, an evolved version of Billbug’s Evora. Sagerunex is a DLL-injected RAT that employs various network strategies to maintain control. Experts have pointed out that the three variants maintain the same core functionalities, supporting the attribution to Lotus Blossom due to consistent targeting patterns and TTPs.
The initial access vector for recent intrusions is unclear, but the threat actor used spear-phishing and watering hole attacks in past campaigns.
Research into the Lotus Blossom attack revealed several tools used to evade detection and achieve their objectives:
- Cookie stealer tool: A Chrome cookie stealer bundled with PyInstaller to harvest browser credentials.
- Venom proxy tool: A customized proxy tool to relay traffic with hardcoded IP addresses.
- Privilege adjuster: A tool to retrieve process tokens and elevate privileges.
- Archiving tool: A custom tool to steal and protect files, including browser data.
- Port relay tool: A modified proxy relay tool, “mtrain V1.01,” for relaying connections.
- RAR tool: Used to archive or zip files.
Talos researchers conducted a detailed analysis of multiple Sagerunex backdoor variants, revealing similarities and highlighting different C2 strategies. The Beta version, distinguished by debug strings, uses Dropbox as a C2 channel. Another variant uses both Dropbox and Twitter for data exfiltration, retrieving host info and sending encrypted data back to the C2 servers. Talos spotted a third variant using Zimbra webmail, employing the Zimbra API for data exfiltration via email drafts. Each variant implements various checks, such as time-based delays and system verifications, to maintain persistence. The malware’s loader injects the backdoor into memory and uses encryption to obfuscate data. Additionally, the use of VMProtect obfuscates the malware code to evade antivirus detection. Talos also identified specific file paths and configuration details, indicating that the malware has been active for years, with ongoing operations likely between 2018-2022. This highlights the long-term persistence and adaptability of the Lotus Blossom group’s tactics.
The report includes Indicators of compromise (IOCs) for these attacks.
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Pierluigi Paganini
(SecurityAffairs – hacking, APT)