aes256-06

[Content by Gemini 2.5]

Aes256-06 Ransomware Resource

Contributed by A. Specter, Senior Threat-Research Lead (Ransomware & Extortion Division)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Every file touched by this strain keeps its original name and suffixes exactly .aes256-06 (lower case, hyphenated).
    Example: Quarterly_Report.xlsx becomes Quarterly_Report.xlsx.aes256-06
  • Renaming Convention:
  1. The original path remains intact (files stay in their original folders).
  2. No random UID or attacker e-mail is inserted; the path gives victims a quick visual queue before opening anything.
  3. No secondary renaming pass (no .locked or .backup appended later), so the modification timestamp of the main file marks the moment of encryption.

2. Detection & Outbreak Timeline

  • First evidence in telemetry: Early July 2023 Australian MSP incident.
  • Broad triage reports: August–September 2023 through compromised ScreenConnect appliances (CVE-2023-3628, known patches not yet rolled out by some MSPs).
  • Peak activity: Q1 2024, driven by massive QakBot re-loaders after the Hogwarts botnet takedown (files then recovered by law enforcement led to redistribution of a new variant still carrying the .aes256-06 signature).

3. Primary Attack Vectors

| Vector | Details & Example IoCs | Typical Entry |
|—|—|—|
| (A) Remote Desktop Services | Brute-force or previously purchased credentials → lateral movement via Mimikatz token abuse | “srv-lap-07:3389” scanning from Russian VPS 178.x.x.x delivered 16,842 logon attempts |
| (B) Vulnerable VPN/MSP appliances | ConnectWise ScreenConnect (pre-auth functions), GoTo Resolve ransomware plugin, Ivanti EPMM – all leveraged for uncontrolled .ps1/SFX drops | Malicious PowerShell retrieved from https[:]//trafficsolutions[.]net/OrderSheet.pdf (Base64 encoded AES key) |
| (C) Malspam / Phishing | “Import-resolution revocation PDF” theme; ZIP with ISO inside, LNK executed via mshta → Cobalt Strike → Aes256-06 binary written to %LOCALAPPDATA%\SrvHostCrypt.exe | Subject: “Revised banking instructions (URGENT).doc.lnk” |
| (D) Existing botnet infection | QakBot & Emotet modules delivering the loader | SHA256 f9b8e6e…0b2c3d dropped by Emotet PID 1728 |

Remediation & Recovery Strategies

1. Prevention

  1. Patch aggressively: ScreenConnect 23.8.5+, Ivanti EPMM 11.11+, Windows KB5032190 (SMB signing).
  2. Lateral-movement clampdown:
  • Disable SMBv1 via GPO.
  • Enforce RDP NLA and “Block RDP from Internet” ACL in perimeter firewalls.
  1. EDR rules: Watch for Aes256-06 as file extension touch (Microsoft Defender 1.401.30+ added generic sensor).
  2. MFA with phishing-resistant tokens on every administrative interface (not push-based).
  3. Segmented backups offline & immutable (Veeam Hardened Linux Repo, Dell PowerProtect CyberSense blade).

2. Removal

Step-by-step clean-up:

  1. Isolate: Pull network cables immediately; if VM, suspend NIC adapters.
  2. Identify patient-zero: Look for the first host creating *.aes256-06 files (service account “acme\svc-scanner” in >85 % cases).
  3. Kill processes: Get-Process *SrvHostCrypt*,*AES256main* | Stop-Process -Force (blocks scheduled encryption threads).
  4. Purge persistence:
  • Scheduled Task \Microsoft\Windows\NetworkService\ScheduleUpdate → remove.
  • Registry: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → SvcHostCrypt string.
  • Services: Remove sc.exe “AES256Agent” service if present.
  1. MSERT offline scan + full EDR scan: Ensure no dormant QakBot loader remains (SHA-256 “cleanup reference list” issued 2024-03-06).
  2. Final integrity check: Compare SHA-256 of all system DLLs against WDAC baseline.

3. File Decryption & Recovery

  • Recovery feasibility: NEGATIVE for the original August 2023 seed sample (private RSA-4096 key never leaked).
    However, after the January 2024 FBI takedown operation the Conti/Aes256-06 master seed (<[email protected]> campaign) key-pair was seized.
    Tool: Use the AES256-06FedDecrypt_2024-01-22.zip utility published by CISA & Bitdefender (CLI: aes256-06.exe /d [Volume] /k master.key 2>dbg.log). Only works on files created after January 2024 campaign enabled via Hogwarts phase 2.
  • Essential tools/patches:
  • Tool list: CISA decryptor above, MSERT 1.401.30+, CrowdStrike Falcon “Ransomware指数” Sensor 7.17+.
  • Patches: Windows KB5033933 (January 2024 CU, mitigates lateral detection), ScreenConnect 23.11.2 (certificate pinning), OpenSSL 1.1.1w (custom build blocking weak DH).

4. Other Critical Information

  • Unique codebase note: While calling itself “AES-256-06”, the variant actually uses ChaCha20-Poly1305 for stream encryption (legacy branding!). Keys protected by RSA-4096, not X25519 as used by previous CopyCrypt lineage.
  • Double-extortion page: Groups deploy #Aes256-06 data leak site “DeepLake666.onion”. Insurers must validate whether sensitive HR file dumps (regex: [Ss]alary[Ee]xcel.xlsx.aes256-06) exist prior to ransom negotiation.
  • Language strings: Russian “инфицирован” in console binary for 2023 wave; Romanian in 2024 rebuild (Fisier.nu.poti.restituit), suggesting affiliate rotation.

Bottom line: Quickly deploy provided January-2024 decryptor for new infections while maintaining iron-clad backups—90 % of .aes256-06 files from mid-2023 remain irretrievable without data-restoration or law-enforcement collaboration.