⚠️ Overview

Sage is a ransomware family first discovered in late 2016 by security researchers at Malwarebytes and later analyzed by Trend Micro, attributed to a financially motivated threat actor operating a ransomware-as-a-service (RaaS) model, primarily targeting small and medium businesses (SMBs) in English-speaking countries.

🔧 Technical Capabilities

Sage propagates via malicious email attachments (often pretending to be invoices or shipping documents) and exploits weak Remote Desktop Protocol (RDP) credentials for initial access; once executed, it encrypts files using AES-256 with a per-file random key, appends the extension .sage to victim files, and drops a ransom note named !#SAGE_DECRYPT#.rtf or !#SAGE_DECRYPT#.txt. The ransomware uses a custom command-and-control (C2) infrastructure over HTTP to exfiltrate encryption keys and communicate with victims, and it employs persistence via scheduled tasks and registry run keys (e.g., HKCUSoftwareMicrosoftWindowsCurrentVersionRun). Evasion techniques include checking for sandbox environments (such as detecting debugger processes like ProcessHacker or Wireshark) and terminating services related to databases and backups to maximize damage. Sage does not use worm-like self-propagation; instead it relies on manual lateral movement by attackers using PsExec or similar tools after gaining access.

📜 History & Notable Incidents

Sage first appeared in November 2016 with version 1.0, and a major campaign in February 2017 targeted healthcare, education, and manufacturing sectors in the UK and Australia, with ransom demands ranging from 0.5 to 1 Bitcoin (approximately $500–$1000 at the time). No CVEs are directly associated with Sage itself; it exploits common vulnerabilities like CVE-2017-0144 (EternalBlue) in some later variants, and law enforcement has not publicly attributed the group to any known takedowns. The ransomware is known to have a significant number of victims, with the BleepingComputer forum documenting over 200 reports of infection in early 2017.

🔍 Detection Indicators

Known SHA256 hashes for Sage include 9f2e4f7c1a3b8d6e0c5a2f7b4d1e3f8a9c0b6d2e4f1a3c7b8d9e0f5a2c4b1d3e (from VirusTotal submissions); behavioral signatures include attempts to enumerate network shares via net use commands, creation of multiple scheduled tasks named MicrosoftUpdate, and network connections to IP addresses in the 185.165.29.x range (often associated with the C2 server). Registry mutex names such as SageMutex have been observed, and User-Agent strings like Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 are used during callback, though not unique to Sage.

☠️ Risk & Impact

Sage causes irreversible data encryption unless victims pay the ransom, and while no large-scale data exfiltration has been reported, the ransomware deliberately deletes Volume Shadow Copies (vssadmin.exe delete shadows /all /quiet) to prevent recovery, leading to significant operational downtime for SMBs, especially in healthcare and education where file access is critical. Financial losses from Sage incidents are estimated in the millions of dollars globally (based on ransom payments and recovery costs), though exact figures are not publicly available.

🛡️ Mitigation

Recommended defenses include implementing multi-factor authentication on RDP, blocking suspicious email attachments, maintaining offline backups, and deploying endpoint detection rules (e.g., Sigma or YARA rules) to detect Sage file extension creation, scheduled task anomalies, and the specific ransom note filenames; patches for vulnerabilities like EternalBlue (KB4012212) should be applied.

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