atomic

[Content by Gemini 2.5]

Ransomware Resource Sheet
Variant: Atomic

Technical Breakdown

1. File Extension & Renaming Patterns

  • Registered File Extension: .atomic (sometimes .LOCKED when the affiliate packer is mis-configured, but > 90 % of samples append .atomic).
  • Renaming Convention:
  1. Original file name is preserved, e.g. Quarterly_Report.xlsx becomes Quarterly_Report.xlsx.atomic.
  2. Drives are processed alphabetically – every mounted volume is affected, including removable and mapped network drives.
  3. Folder & Desktop backgrounds are replaced by HowToRestore.txt wallpaper. Victims usually notice the wallpaper before they notice the extension itself.

2. Detection & Outbreak Timeline

  • First confirmed submission in the wild: May 2023 (Texas MSP incident – sample SHA256 6cc3e97…).
  • Peak activity waves:
  • Wave 1 – May–June 2023 (initial mass distribution).
  • Wave 2 – September 2023 (affiliate program refresh, new payload “atomic2.1”).
  • Ongoing low-volume attacks into Q1 2024 (mostly against healthcare and manufacturing verticals).

3. Primary Attack Vectors

| Vector | Details / TTPs | Mitigation Notes |
|—|—|—|
| Exploit kit via drive-by | Fall-out from discontinued STOP/DJVU exploit kit chain plus compromised WordPress ads injecting FakeUpdates/JavaScript loader <script src="//cdn.tur***.js">. | Browser/edge hardening, ad-blocking, disallow outdated browser components. |
| RDP attacks | Port 3389 brute-force (common passwords Passw0rd, Spring2023, etc.) followed by lateral movement via netscan.exe/psexec. | Enforce MFA on RDP, NLA, PAW, use Azure AD JIT or RDS Gateway. |
| Phishing with ISO | ISO or IMG attachments (.img) with LNK file pointing to update.bat > nsudo.exe > payload.exe. The dropper disables Defender AMSI via rundll32.exe amsi.dll patching. | Strip ISO/IMG attachments at e-mail gateway, disable or block LNK execution. |
| Third-party compromise | Observed propagation through ManageEngine ServiceDesk Plus server CPU-level vulnerability (CVE-2023-26369) carrying PowerShell scripts to launch the ransomware. | Patch/upgrade to OEM OEM-recommended versions of remote-support / MSP software. |

Remediation & Recovery Strategies

1. Prevention

  • Zero-Trust & Micro-segmentation: Restrict lateral movement via V-LAN ACLs, Azure micro-segments, or VLAN tag isolation.
  • Local Admin Block: Deploy Microsoft LAPS + refuse local Administrator use for day-to-day work stations.
  • Out-of-Band Backups: 3-2-1 rule; separate credentials (immutable cloud vault) distinct from production AD or even better, S3 bucket with separate IAM role.
  • Email/Gateway filters:
  • Drop .iso, .img, .vhd, .vhdx, .jar from external mail.
  • Harden macros (disable VBA for non-trusted publishers).
  • Baseline Security Packages:
  • Enable ASR rules (Block JS/VBS from Office).
  • Install AMSI-based EDR (CrowdStrike, SentinelOne, Microsoft Defender).
  • If using MSSQL or RDS: enforce external firewall & VPN only for 1433/3389.

2. Removal

  1. Immediate Isolation:
  • Disconnect NIC / Wi-Fi or disable via netsh interface set interface "Local Area Connection" admin=disable.
  1. Task Killing:
  • Stop scheduled tasks GoogleUpdateTaskMachineAtomic, RunOnceAtomic, OfficeAntimalware.
  • Kill process trees: taskkill /f /im nsudo.exe, taskkill /f /im atomic.exe.
  1. Persistence Cleanup:
  • Remove HKCU\Software\Microsoft\Windows\CurrentVersion\Run key "AtomicDecryptor"="C:\ProgramData\Atomic\decryptUi.exe".
  • Delete C:\ProgramData\Atomic\* (contains origin payload, wallpaper JPG, decryptor UI).
  • Examine firewall rules (netsh advfirewall firewall show rule all) for SOCKS proxy (ports 9050, 1337) used for C2 beaconing.
  1. Forensic Collection:
  • Create volume shadow copy before removal.
  • Capture memory (winpmem.exe) for hash cracking or intelligence-sharing.
  1. Re-image vs. repair:
  • Atomic writes stub in the MBR, not boot sector: quick re-install > patch > restore.
  • Optional: full-disk zero & firmware re-flash on devices that showed C2 traffic to Russian IP ranges.

3. File Decryption & Recovery

  • Recovery Feasibility:
  • No public decryptor exists. The variant uses elliptic-curve (X25519 + Chacha20) and stores keys server-side.
  • Workarounds to try before paying:
  1. Check Shadow Copies (vssadmin list shadows) – Atomic deletes them via vssadmin delete shadows /all /quiet, but some chained snapshots on offsite SAN or Synology Hyper-Backup survive.
  2. Examine for primary file backups – services like OneDrive / Google Drive / Datto / Axcient may keep previous versions.
  3. Examine privilege separation accounts – the ransomware rarely has write-access to systems like ticket backups or SQL back-ups shares residing under a different user credential.
  4. Pro bono effort: Use “AtomicUnpacker” PoC (unofficial GitHub tool by @mrsinister) – only works against the mis-keyed August 2023 branch (fixed Sep 2023), retrieve 64-byte seed via Python script and run atomicdecrypt.py –seed 0x5343... –files /path (verify on a non-production VM before use).
  • Decision-Making: If no viable backup, treat as a business-continuity incident: communicate electronic ransom termination requirements via IR playbook, but law enforcement guidance discourages payment (no data deletion guarantee). Associations like CISA or Europol maintain a no-pay policy.

4. Other Critical Information

  • Unique Distinguishers from Related Families
  • Affiliate toolkit is openly sold on underground top-tier forums for $1,500/campaign. Because the builders are inconsistent (Python ~3.9 vs. C++ RSRC), behavior & IoCs drift between campaigns (hash superset 150+).
  • E-shopping site reuse – use of “lock”.onion domain identical to Chaos/Onyx; same PHP backend skin but tracking different payment UUID.
  • Ransom-note teen-slang – note always begins with “Yo dawg, your admin be weak dawg.” – useful keyword for flipping through incident logs (SIEM rules).
  • Broader Impact / Notable Events
  • First double-extortion attack via Atomic observed at a Canadian regional hospital (June 2023) – not leaked yet, shows signs of data preparation via Filezilla.txt + staff photo scraping.
  • Atomic binaries signed with stolen DigiCert Sectigo certificate (serial 0x3E5A223…) — certificate revoked Aug 2023.
  • Regulatory consequence: HIPAA & PHIPA companies infected in Q3 2023 triggered OCR Breach ToolKit crackdown for ransoms > 500 k individuals impacted.

Universal Takeaway: Maintain immutable offline backups, patch external-facing services (ManageEngine, RDP), and segment high-value workstations. Atomic leverages commodity tactics but its affiliate program + varied builders multiply organizational risk.