ARC Labs analyzed the Wineloader backdoor, detailing its infection chain, obfuscation techniques, and defense opportunities with detection guidance for Microsoft Sentinel. The report covers HTA JavaScript analysis, DLL sideloading, and persistence mechanisms tied to APT29-linked activity, providing actionable indicators and detection queries. Hashtags: #Wineloader #APT29 #NOBELIUM #COZYBEAR #BurntBatter #BeatDrop #MuskyBeat
Keypoints
- Wineloader is a modular backdoor used in spearphishing campaigns attributed to APT29 (NOBELIUM/COZY BEAR) that can download modules via an encrypted C2 channel.
- The phishing lure involves an invite to a wine tasting event hosted by the Ambassador of India, leading targets to a malicious site.
- The infection chain downloads a ZIP containing an obfuscated HTA with JavaScript, which then downloads another ZIP with the Wineloader payload.
- Wineloader executes via a DLL sideload into sqlwriter.exe and can be launched directly via mshta.exe, aiding defense evasion and reducing spawned processes.
- Persistence is achieved through scheduled tasks or Registry Run keys (HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRunMS SQL Writer).
- ARC Labs provides threat-hunting queries and guidance for detecting Wineloader activity in Microsoft Sentinel and notes potential second-stage payloads from the C2 server.
<liObfuscation techniques include heavily obfuscated JavaScript with variable renaming and string encoding; defenders can study arrays and replace functions to decode payload data.
MITRE Techniques
- [T1566.002] Spearphishing Link – Phishing email invites targets to wine tasting; “The campaign starts with a phishing email inviting targets to a wine tasting event hosted by the Ambassador of India.”
- [T1105] Ingress Tool Transfer – The malicious website downloads a ZIP file containing a malicious HTA file with heavily obfuscated JavaScript code.
- [T1059.007] JavaScript – The HTA contains heavily obfuscated JavaScript, including variable renaming and string encoding.
- [T1574.002] DLL Side-Loading – The malicious DLL is loaded automatically when sqlwriter.exe executes because of the DLL search behavior.
- [T1218.005] Mshta – Recreation shows direct launching of code through mshta.exe without an extra process.
- [T1053.005] Scheduled Task – Persistence via scheduled tasks (and registry changes).
- [T1547.001] Run Keys / Startup Folder – Persistence via Run key: HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRunMS SQL Writer.
Indicators of Compromise
- [File] text.txt – an encoded archive containing sqlwriter.exe and vcruntime140.dll
- [File] sqlwriter.exe – the payload loaded as part of the final stage
- [File] vcruntime140.dll – the DLL included in the encoded archive
- [Process] mshta.exe – used to execute the payload sequence
- [Registry Key] Run key – HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRunMS SQL Writer
Read more: https://www.binarydefense.com/resources/blog/wineloader-analysis-of-the-infection-chain/