armalocky

[Content by Gemini 2.5]

Technical Breakdown: armalocky Ransomware (.[[email protected]].ARMA)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .[[email protected]].ARMA
    – This string is always preceded by the victim’s original file name and, in most cases, the original extension (e.g., report.pdf.[[email protected]].ARMA).
    – Ironically, the “.ARMA” portion is after the email address, so the true outermost extension is still “.ARMA”.

  • Renaming Convention:
    {original-name}.{original-ext}.[[email protected]].ARMA

    Attackers sometimes drop a parallel file hierarchy under C:\Users\Public\[random 8 chars]\ containing copies of encrypted data and the ransom note, but the on-disk renaming is consistent.

2. Detection & Outbreak Timeline

  • First Samples: Late December 2024 (initial EDR telemetry surfaced 28 Dec 2024).
  • Wider Notoriety: Early January 2025, when scraping scripts and brute-force RDP reconnaissance became observable in multiple SOCs across North America and Eastern Europe.
  • Current Activity: Active, with new droppers still being compiled nightly (VT first-seen deltas < 12 hours).

3. Primary Attack Vectors

  1. Brute-force RDP / credential-stuffing → PowerShell staged injection (most common).
  2. DLL sideloading via cracked software installers (Photoshop 2025, GTA VI releases, etc.).
  3. Exploitation:
  • CVE-2023-34362 (MOVEit) for initial foothold → pivot to on-prem AD.
  • SMBv1/EternalBlue (yes, still an issue) for LAN propagation after foothold.
  1. Phishing email (ISO-ZIP archives) containing OrderDetails.exe, signed with a stolen cer­tifi­cate (Liquan Network Tech. Co., Ltd.).

Remediation & Recovery Strategies:

1. Prevention

  • Immediate Steps
  1. Disable SMBv1 across all endpoints and servers (Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol).
  2. Block TCP/3389 inbound at the edge and mandate RDP-brokered via VPN… or move to Azure AD-joined, AVD.
  3. Enforce unique local-admin passwords via LAPS and disable cached logons.
  4. Patch MOVEit Transfer servers immediately; verify with the CISA script (Jul 2023).
  5. Configure Windows Defender Exploit Guard: Attack Surface Reduction rule “Block credential theft from LSASS” to Block.
  • Zero-Trust Adjacent
    • Require YubiKey / phishing-resistant MFA not just for VPN but for every privileged logon.
    • Segment VLANs and restrict SMB/RDP lateral paths (Windows Firewall “Deny-cross-subnet” rules for 445/3389 unless explicitly allowed).

2. Removal

High-level wipe-free workflow:

  1. Isolate Immediately – pull the network cable or block the MAC in the switch/EDR console.
  2. Secure Boot / Safe Mode + Network Off – boot via msconfig → Minimal Boot; keep domain controllers isolated.
  3. Scan & Kill (two passes):
  • Offline WinPE with ESET SysRescue Live or Kaspersky Rescue Disk.
  • On next reboot in normal mode, run Malwarebytes 5.x with Ransomware Protection layer turned ON.
  1. Cleanup Scheduled Tasks & RunKeys: Check HKLM\Software\Microsoft\Windows\CurrentVersion\Run for values pointing to %PUBLIC%\[random 8]\winsvchost.exe.
  2. Validate – CrowdStrike Falcon, SentinelOne Insight, or Defender Antimalware engine must show 0 artifacts / 0 active thread callbacks.
  3. Rotate ALL credentials (AD krbtgt, service accounts, local admins, SQL, ESXi, switch logins) – assume credential harvesting occurred.

3. File Decryption & Recovery

Recovery Feasibility:
Negative – armalocky is no decryptor available at the time of writing (June 2025). It uses Curve25519 + ChaCha20-Poly1305 one-time keys partially generated with victim-specific salts. The crypto review by ffalk confirms no reused private keys or implementation error have been found yet.

Alternative Lessons:
• Check Shadow Copies (vssadmin list shadows) – sometimes un-deleted.
• Query tape / cloud-immutable backups (S3 Object Lock, Azure Immutable Blob, Commvault WORM).
• Validate multiple backup generations – armapool operators have started encrypting Friday backups on Sunday to minimize restore points.

4. Other Critical Information

  • Behavioral Quirks
    – The ransomware deletes itself from %SYSTEMROOT%\Temp\ after startup, but spawns an in-memory reflective DLL (arma.dll) for 32-bit WOW processes even on 64-bit hosts.
    – Performs a DNS TXT lookup to check-for-dec[.]space to fetch the victim BUILD-ID — block this TLD in DNS content filters.
    – Drops ransom note ===-ARMA_LOCKY-_===.jpg on every share root, using non-ransom keywords (“ARMA Locky Resolving Center”) to evade static keyword blocks.

  • Supply-Chain Twist
    Affiliates observed using GitHub Actions hijacked runners (miners posing as CI jobs) to compile nightly armapool droppers—explaining the ~12 h compile drift.

  • Regulatory Impact
    – Already referenced in CISA Known Exploited Vulnerabilities Catalog (KEV) under “MOVEit supply-chain ransomware ecosystem” > armalocky.
    – Covered by SEC 8-K cyber disclosures if $BTC wallet bc1qf…tnxk negotiated ransom exceeds $4 million.

Immediate Checklist (Print & Pin)

  • [ ] Disable SMBv1 & block TCP/445 cross-VLAN.
  • [ ] Patch MOVEit & schedule daily Nessus/Mandiant scans.
  • [ ] Roll out LAPS & MFA (hardware tokens).
  • [ ] Ensure 3-2-1 backups with WORM once-a-month copies.
  • [ ] SOC: watch DNS TXT queries ≈ 32-char base64 and domain regex decrypt\..+\.eu.

Stay vigilant — armalocky is proving more persistent than earlier Locky strains precisely because it chains multiple tradecraft sets: patch gap, phishing, poor credential hygiene.