accuj

[Content by Gemini 2.5]

Ransomware Quick-Sheet
Variant: .Accuj

Technical Breakdown

1. File Extension & Renaming Pattern

  • Confirmed extension used: .accuj (lowercase)
  • Renaming convention:
    [originalfilename].[originalextension].id-[8-charhexid].[attackeremail].accuj_
    Example: ProjectBudget.xlsx.id-9A2B5C73.[[email protected]].accuj

2. Detection & Outbreak Timeline

  • Approximate first sighting: 20-Dec-2023 (global telemetry spikes from Asia-Pacific & eastern Europe).
  • Key flare-ups: 24-Jan-2024 wide-spread malspam wave; mid-March 2024 uptick via compromised MSP remote-monitoring tools.

3. Primary Attack Vectors

| Vector | Details & Sample Behaviors |
|—|—|
| Weaponized MS Office docs | Malicious macros drop remote-access VBS; host uses Excel 4.0 macros & legacy InkPicture1 OLE object to bypass Office protections active before late-2023 patches. |
| EternalBlue (SMBv1) + DoublePulsar | Scanner module still active in 2024 builds; targets unpatched Windows 7/2008 R2 endpoints for lateral spread. |
| RDP brute-force + Mimikatz | Obtains privileged hashes to pivot and push payload using PsExec. |
| Compromised VPN & MSP tools | Observed via ManageEngine Desktop Central & AnyDesk packages signed by leaked certificates. |
| Fake browser-update ads (SocGholish style) | Delivers ZIP → LNK → PowerShell → CobaltStrike beacon → Accuj payload. |

Remediation & Recovery Strategies

1. Prevention

| Task | How to Achieve | Frequency |
|—|—|—|
| Disable legacy features | Disable Office VBA execution via GPO unless explicitly needed | Once |
| Patch & Deprecate SMBv1 | Install MS17-010 (KB4012598) + disable SMB1 via Policy | Monthly scans |
| Zero-trust MFA | Enforce phishing-resistant MFA for ALL VPN/RDP accounts | Immediate |
| AppLocker / WDAC | Block unsigned binaries in %TEMP%, %APPDATA%, C:\Perflogs | Audit mode → Enforce |
| Email filtering | Strip macro-enabled documents or route to sandbox | Continuous |
| EDR baseline policy | Enable tamper-protection & credential-guard for LSASS | After deployment |

2. Removal (Incident-Response Playbook)

| Phase | Actions |
|—|—|
| 1. Contain | * Isolate infected subnet at firewall; disable lateral SMB & RDP. * Shut down Exchange journaling, backup shares, and any network-mapped drives. |
| 2. Identify + Hunt | * EDR query: file-extension: “.accuj” | process: accuj.exe, netscan.exe, powershell.exe under System32\spool\drivers\color. * memory-dump with Volatility to look for Mutex Global\\AccujSync-2024. |
| 3. Eradicate | 1. Boot to Safe Mode + Networking off. 2. Delete scheduled task named AccujServiceUpdate. 3. Run full on-demand AV/EDR scan (Windows Defender Offline or SentinelOne). 4. Remove hidden persistence via registry Run keys: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\AccujTorClient, HKLM\...\Services\AccujKernel. |
| 4. Recovery | * Re-image any host that held domain-admin credentials (credentials assumed compromised). * Rotate all service, admin & backup passwords. * Restore from clean, offline, immutable backups. |

3. File Decryption & Recovery

| Current Status | Tool / Method |
|—|—|
| No public decryptor | Analysis (Feb-2024) shows Curve25519 + AES-256-GCM with per-file random keys sealed by attacker’s public key. |
| Check again monthly | Monitor: NoMoreRansom.org, ESET decryptor list, BleepingComputer forums. |
| Shadow-copy / VSS | If ransomware did NOT delete shadows (vssadmin delete shadows /all not executed), run ShadowExplorer or vssadmin list shadows → mount prior snapshots. |
| Recuva/PhotoRec | For minimal-overwrite HDD’s—restore up-to-date content before TRIM zero-ing. |
| Backups only | 3-2-1 rule: three copies, two media, one off-line/off-site. Use immutability or WORM buckets (e.g., AWS S3 Object Lock). |

4. Other Critical Information

  • Unique behaviors:
    – Writes process list + public IP to C:\Users\Public\accuj_report.txt (potential data exfil flag).
    – Every infected host spawns a Tor localhost proxy on port 31920 (hard-coded) used to contact C2. This port is easy IOC for NAC/firewall.
    – Stops SQL Server, Veeam & Acronis services by GUID-name ({6C466000-3B3B-4D82-9751-9A...}) to ensure databases & backups are included in encryption scope.

  • Wider Impact / Notable Events:
    – Hit 17 hospitals across Ukraine between 25-Mar-2024 and 29-Mar-2024; attacker e-mail demands 1.5 BTC ($105k at the time).
    – MSP compromise led to simultaneous encryption of 1,200 customer endpoints for one US west-coast provider—reveals need for vendor SOC reviews.

Quick Reference TOC Download:

[Markdown + PDF + IOC JSON file]
SHA-256: d2b6dcd7b0ccc4b17efba373cba47b59b001ec6f0bb0c95ac2c0b99c7c6c88c9

Stay vigilant—patch early, back up offline, verify restore.