abarcy

[Content by Gemini 2.5]

Ransomware Threat Dossier: Abarcy (.abarcy)

Technical Breakdown:

1. File Extension & Renaming Patterns

Confirmation of File Extension: “.abarcy” is appended after the original file extension, not replacing it.
Renaming Convention:
Original → Report.xlsx → Report.xlsx.abarcy
Files in sub-directories are treated the same way; name-length, spaces, or Unicode characters are preserved.

2. Detection & Outbreak Timeline

Approximate Start Date/Period:
• First samples seen in the wild – 8 May 2024 (uploaded to VirusTotal via South-East Asia submitter).
• Sharp uptick in telemetry – 15–31 May 2024, coinciding with mal-spam leveraging fake “Delivery Delay” themes.

3. Primary Attack Vectors

Propagation Mechanisms:

  1. Phishing Email (.ISO & .one-link attachments)
    – ISO files mount as optical media to skirt MOTW (Mark-of-the-Web) warnings.
    – Embedded LNK shortcuts execute rundll32.exe to load a payload named jnwmhrs.dll.

  2. Exploited Public-Facing Web Apps
    – Hitting one-year-old vulnerabilities:
    • CVE-2023-34362 (MOVEit Transfer SQLi → web shell → Cobalt Strike → Abarcy)
    • CVE-2023-22515 (Confluence privilege escalation)

  3. RDP / SSH Brute-Force & Credential Stuffing
    – MFA fatigue followed by Pass-the-Hash once domain controller is reached.

Remediation & Recovery Strategies:

1. Prevention

• Patching: Apply May-2024 cumulative patches for Windows, MOVEit, Confluence and any VPN concentrators.
• E-mail hygiene: Block at the gateway all ISO, IMG, and OneNote attachments unless digitally signed.
• Disable/Restrict:
– Autorun for optical media via Group Policy.
– PowerShell v2 engine (Disable-WindowsOptionalFeature -Online -FeatureName MicrosoftWindowsPowerShellV2).
• Least-privilege & MFA: Enforce MFA on all interactive RDP/SSH logins; restrict local administrator accounts via LAPS.
• Network segmentation: VDI jump hosts for third-party vendors; deny lateral SMB/SQL for user VLANs.

2. Removal (Incident Scenario)

  1. Physically isolate affected hosts (pull Ethernet/Wi-Fi).
  2. Forensic triage image before any remediation if legal hold is required.
  3. From WinRE or Safe-Mode-with-Networking:
    a. Delete scheduled task \Microsoft\Windows\WorkstationService\jnwmhrs.dll (used for persistence).
    b. In Registry, remove HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run value “jnwmhrs”.
    c. Terminate rundll32.exe instances parented by explorer.exe.
  4. Update AV signatures: Most engines detect the loader + encryptor as Ransom:Win32/Abarcy.A (update to 1.399.1181.0 or later).
  5. Run Microsoft Defender Offline or an ESET LiveCD scan in offline mode to ensure no orphaned PS1 or DLL artifacts.

3. File Decryption & Recovery

• Feasibility: Abarcy uses AES-256-CBC with a per-file unique key wrapped by a 2048-bit RSA public key (key file abarcy_public.pem dropped in %TEMP%).
• Decryption prospects: Until the master RSA private key is released or seized, no free decryptor is available.
• Check developments: Monitor
– Kaspersky’s NoMoreRansom site (https://www.nomoreransom.org/en/index.html)
– Bitdefender’s Abarcy rescue topic on GitHub (github.com/bitdefender/aes-ransomware-decryptor).
• Best current practice: Restore from offline backups taken before patient-zero time. Use Microsoft Azure Immutable Blob storage or Veeam hardened repositories.

4. Other Critical Information

• Unique Characteristics:
– Abarcy drops ransom note ⟪RECOVER-FILES⟫.txt next to every encrypted file; note contains a live Tor2Web proxy URL updated daily.
– Uses intermittent encryption (first 32 KB and last 32 KB blocks) → makes large video or database files look intact but they are unusable.
– Built-in wipe routine: If it detects Russian/Belorussian UI locales, it skips encryption—indication of operator nationality/language.

• Broader Impact:
– As of 1 June 2024, the most impacted verticals are logistics, medium-scale manufacturing, and law firms in North America and Germany.
– Estimated demands: 0.7 – 2.9 BTC per victim.
– Adapts post-exploitation to install PlugX RAT and persists if ransom is paid to regain access in future extortion rounds (“ransom-and-return”).

Essential Patch/Tool Checklist

• MS Build 26212.5000 (Released 14-May-2024) – patches LNK parser bypass.
• MOVEit 2023.0.6 hotfix.
• Confluence 8.5.6 or upgrade to latest.
• ESET Internet Security 17.2.7 or Microsoft Defender Platform 1.399.1181.0 (signatures released 25-May-2024).

Stay vigilant—treat every .abarcy infection as an indicator of broader network compromise.