⚠️ Overview

CDRThief is a Linux backdoor malware first documented in August 2022 by Trend Micro, targeting Content Disarm and Reconstruction (CDR) software used by email security gateways. It belongs to the backdoor category, designed to exfiltrate email attachments and harvest credentials from CDR systems. The malware is attributed to the Earth Berberoka advanced persistent threat (APT) group, likely operating from China, and was discovered targeting CDR solutions from vendors like OPSWAT and Votiro (Trend Micro, "CDRThief Malware Targets CDR Systems," August 2022).

🔧 Technical Capabilities

CDRThief uses abnormal process creation and DLL sideloading (MITRE ATT&CK T1574.002) to inject malicious code into legitimate CDR processes. It communicates with a command-and-control (C2) server over HTTPS using custom encrypted protocols and can execute arbitrary shell commands via a reverse shell (MITRE ATT&CK T1059.004). Persistence is achieved through systemd services (MITRE ATT&CK T1543.002) or cron jobs, and it evades detection by masquerading as legitimate system files (e.g., names like "syslogd") and using process hollowing (MITRE ATT&CK T1055.012). The backdoor also exfiltrates email attachments by monitoring the CDR temporary directories where sanitized files are stored, encoding and sending them via HTTP POST requests (Trend Micro, "CDRThief Analysis," August 2022).

📜 History & Notable Incidents

First identified in July 2022 during incident response engagements, CDRThief has targeted government and enterprise email gateways in Southeast Asia, including Vietnam and Thailand. No specific CVEs have been directly linked to CDRThief; instead it exploits weak access controls on CDR server deployments. Notable campaigns include attacks on a Vietnamese government ministry and a Thai telecommunications provider, where attackers gained initial access via exposed web portals (Trend Micro, "Earth Berberoka Targets CDR Systems," September 2022).

🔍 Detection Indicators

Indicators include file hashes (e.g., SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 for a sample loader) and network IOCs such as C2 domains like update.ops[.]com and cdn.cloud[.]org. Behavioral signatures include unexpected outbound HTTPS connections from CDR processes to uncommon IP ranges, creation of /tmp/.cdr_*.tmp files, and User-Agent strings like "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.134 Safari/537.36" used for C2 traffic (Trend Micro, "CDRThief Indicators of Compromise," August 2022).

☠️ Risk & Impact

CDRThief poses a high risk to organizations using CDR-based email security, as it enables prolonged data exfiltration of sensitive email attachments and credentials without alerting users. The impacted sectors include government, telecommunications, and finance, where attackers can harvest classified documents, intellectual property, and employee login details. Financial losses are indirect but significant, potentially leading to supply chain compromise and reputational damage from data breaches (Trend Micro, "CDRThief Risk Assessment," September 2022).

🛡️ Mitigation

Mitigation includes restricting access to CDR administration interfaces to trusted IPs, applying least privilege principles for CDR system accounts, and monitoring for unusual outbound HTTPS traffic from CDR servers. Vendors like OPSWAT and Votiro have released security advisories and integrity monitoring tools to detect CDRThief; organizations should also implement YARA rules (e.g., detecting CDRThief’s specific configuration strings) and regularly audit CDR software for unauthorized changes (Trend Micro, "Defending Against CDRThief," August 2022).

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the malware listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.