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UNC4841 is a China-nexus cyber espionage threat actor assessed to operate in support of the People’s Republic of China. The group is best known for long-running exploitation of Barracuda Email Security Gateway appliances, including the zero-day vulnerability CVE-2023-2868, to obtain durable access across multiple regions and sectors. Reporting links the actor to sustained espionage activity rather than financially motivated operations, with victim organizations spanning public and private sectors worldwide and a notable impact on government entities. UNC4841 specializes in compromising edge devices and other security appliances that often have limited defensive visibility. In Barracuda ESG intrusions, the actor deployed a tailored malware ecosystem including SALTWATER, SEASPY, SEASIDE, SEASPRAY, SKIPJACK, WHIRLPOOL, DEPTHCHARGE, and the SANDBAR rootkit. These tools provided remote command execution, reverse shell access, proxying and tunneling, passive backdoor functionality, stealth, and persistence. The actor repeatedly modified malware components during remediation efforts, used time-stomping to conceal activity, and established persistence through cron jobs, startup modifications, trojanized Lua modules, and configuration-database abuse. DEPTHCHARGE notably enabled reinfection of replacement appliances through contaminated backup configurations. Observed tradecraft includes exploitation of zero-day and n-day vulnerabilities for initial access, trojanization of legitimate Barracuda modules, passive and trigger-based backdoors, abuse of native platform functionality, defense evasion through log suppression and timestamp manipulation, targeted collection from email stores, and exfiltration of staged archives over encrypted channels. UNC4841 has also conducted limited internal reconnaissance and scanning after compromise. The actor’s operations emphasize stealthy, long-term access and selective intelligence collection, including targeting of government-related communications and individuals of intelligence interest in Asia. Infrastructure analysis indicates overlap with other China-linked espionage activity, including reporting of shared or related infrastructure patterns with Salt Typhoon. Available evidence supports a China-nexus assessment, but does not establish that these clusters are the same operator. UNC4841 remains a notable example of PRC-aligned intrusion activity focused on edge-device exploitation, persistence on specialized appliances, and long-term espionage collection.
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Who, where, and (when attributed) which flag flies behind the operation. Pulled from open-source reporting and Mallory's analyst review.
Sectors the actor has been observed targeting.
Geographies tied to known operations.
Attributed origin per open-source reporting.
24 distinct techniques observed across reporting, grouped by tactic. Hover any cell for the evidence excerpt; click through for MITRE's full description.
9 malware families attributed to this actor across reporting.
4 additional families tracked in Mallory.
2 CVEs this actor has used in observed campaigns. 2 of them exploited in the wild.
...UNC4841 exploited Barracuda ESG zero-day vulnerabilities... malicious email attachments to trigger remote command injection in the ESG attachment-scanning component (CVE-2023-2868)... Crafted .tar archives abused Perl’s qx operator to execute arbitrary system commands...
Barracuda later disclosed follow-on exploitation of CVE-2023-7102 in the Spreadsheet::ParseExcel library, again via malicious Excel attachments, to reinstall updated SEASPY and SALTWATER variants after initial remediation.
41 indicators attributed to this actor: domains, IPs, hashes, and other artifacts pulled from reporting. View more in app.
19 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Referenced only because overlapping WHOIS/IOC registration data was observed with infrastructure tied to Earth Estries activity; the report explicitly says there is insufficient evidence to treat UNC4841 as a subgroup of Earth Estries.
China-nexus espionage activity exploiting Barracuda Email Security Gateway (ESG) vulnerabilities (notably CVE-2023-2868 and later CVE-2023-7102) via malicious attachments to gain code execution on ESG appliances, then deploying bespoke implants (SALTWATER, SEASPY, SEASIDE) for persistence, command execution, tunneling, and exfiltration; linked to compromise of Belgium’s VSSE email flows.
China-nexus espionage activity exploiting Barracuda Email Security Gateway vulnerabilities (notably CVE-2023-2868 and later CVE-2023-7102) via malicious attachments to gain code execution on ESG appliances, then deploying bespoke implants (SALTWATER, SEASPY, SEASIDE) for persistence, command execution, tunneling, and exfiltration; linked to compromise of Belgium’s VSSE email flows.
China-nexus espionage activity exploiting Barracuda Email Security Gateway (ESG) vulnerabilities (including CVE-2023-2868 and later CVE-2023-7102) via malicious attachments to gain and maintain persistent access to email gateway infrastructure, enabling long-term collection/exfiltration (including reported compromise of Belgium’s VSSE email flows).
Match sector + geo + tech-stack targeting against your real footprint.
Every observed MITRE ATT&CK technique, grouped by tactic.
Families this actor is known to deploy, with IOCs and behavior.
CVEs this actor has used in known campaigns.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Domains, IPs, and hashes tied to this actor, refreshed continuously.