Cobalt Strike Being Distributed to Unsecured MS-SQL Servers – ASEC BLOG

Cobalt Strike is being distributed to unsecured MS-SQL servers, leveraging brute force, dictionary attacks, and command execution to deploy a memory-based beacon. The campaign overlaps with other malware like Lemon Duck, Kingminer, and Vollgar that abuse port 1433 for scanning and lateral movement within Windows environments. #CobaltStrike #LemonDuck

Keypoints

  • The ASEC analysis team observed the distribution of Cobalt Strike targeting unsecured MS-SQL servers.
  • MS-SQL servers are commonly attacked via unpatched vulnerabilities, brute forcing, and dictionary attacks against the admin account (sa).
  • Attackers scan port 1433 to identify MS-SQL servers publicly reachable, and Lemon Duck is noted for lateral movement via this port.
  • If login succeeds, attackers use commands like xp_cmdshell to run tools; Cobalt Strike is downloaded through cmd.exe and powershell.exe via the MS-SQL process.
  • Cobalt Strike is loaded through MSBuild.exe with techniques to bypass detection, including using a loader into wwanmm.dll to run a beacon in memory.
  • AhnLab ASD logs show multiple Cobalt Strike indicators over the past month, suggesting the same attacker activity across several download and C2 domains.
  • AhnLab emphasizes memory- and behavior-based detection to counter the beacon and recommends their TIP platform for IOC details.

MITRE Techniques

  • [T1046] Network Service Scanning – The attacker or malware usually scans port 1433 to check for MS-SQL servers open to the public. β€˜The attacker or the malware usually scans port 1433 to check for MS-SQL servers open to the public.’
  • [T1110] Brute Force – Attacks include brute forcing or dictionary attacks against the admin account (β€˜sa’) to attempt logging in. β€˜brute forcing, and dictionary attack against poorly managed servers.’
  • [T1021] Lateral Movement – Lemon Duck scans port 1433 and spreads for the purpose of lateral movement in the internal network. β€˜Lemon Duck malware that scans port 1433 and spreads for the purpose of lateral movement in the internal network.’
  • [T1059] Command and Scripting Interpreter – Cobalt Strike was downloaded through cmd.exe and powershell.exe via the MS-SQL process. β€˜downloaded through cmd.exe and powershell.exe via the MS-SQL process as shown below.’
  • [T1055] Process Injection – The injector decodes and injects Cobalt Strike into MSBuild.exe, loading wwanmm.dll and writing/executing a beacon in DLL memory. β€˜injector that decodes the encoded Cobalt Strike inside, and executes and injects the normal program MSBuild.exe.’
  • [T1027] Obfuscated/Compressed Files and Information – The loader decodes the encoded Cobalt Strike inside to execute it. β€˜injector that decodes the encoded Cobalt Strike inside, and executes and injects the normal program MSBuild.exe.’
  • [T1562] Impair Defenses – The Cobalt Strike settings data show a method to bypass detection of security products. β€˜bypass detection of security products, where it loads the normal dll wwanmm.dll, then writes and executes a beacon in the memory area of the dll.’
  • [T1071] Application Layer Protocol – The C2 infrastructure uses HTTP-based URLs for command and control and beacon communications. β€˜C&C
    – hxxp://92.255.85[.]83:7905/push … hxxp://92.255.85[.]94:83/ga.js’

Indicators of Compromise

  • [MD5] Cobalt Strike (Stageless) – ae7026b787b21d06cc1660e4c1e9e423, 571b8c951febb5c24b09e1bc944cdf5f, and other 5 hashes
  • [MD5] CobaltStrike (Stager) – 2c373c58caaaca0708fdb6e2b477feb2, bb7adc89759c478fb88a3833f52f07cf
  • [File name] Detections – Trojan/Win.FDFM.C4959286, Trojan/Win.Injector.C4952559, Infostealer/Win.AgentTesla.R470158, and other 4 detections
  • [File name] Detections – Trojan/Win.Agent.C4897376, Trojan/Win32.CobaltStrike.R329694, and 1 more
  • [Behavior] MD5-based detection – Malware/MDP.Download.M1197
  • [URL] C2 / download URLs – hxxp://92.255.85[.]83:7905/push, hxxp://92.255.85[.]83:9315/en_US/all.js, and 7 more URLs
  • [URL] Beacon download URL – hxxp://92.255.85[.]93:18092/jRQO, hxxp://92.255.85[.]93:12031/CbCt
  • [URL] Download URL – hxxp://45.64.112[.]51/dol.exe, hxxp://45.64.112[.]51/mr_robot.exe, and 7 more URLs
  • [IP] C2 / download endpoints – 92.255.85.83, 92.255.85.86, and other similar addresses

Read more: https://asec.ahnlab.com/en/31811/