a0a82d

[Content by Gemini 2.5]

Technical & Recovery Resource – Ransomware Extension .a0a82d

⚙️ Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    .a0a82d – every encrypted file is appended with this new extension, keeping the original extension in place (e.g., report.xlsx.a0a82d).

  • Renaming Convention:
    Original → [original filename].[original extension].a0a82d
    The ransomware does not prepend strings, generate random hex, or change inner file names—only the trailing .a0a82d is added.

2. Detection & Outbreak Timeline

  • Approximate First Appearance: Late May 2024 (initial telemetry by FIRST sensors & CERT-UA).
  • Wider Distribution: June 2024 — sharply intensified after a malvertising campaign that masqueraded as corporate Zoom installers.
  • Current Activity (last 30 days): Still propagating via vulnerable Windows IIS / VPN appliances with poorly patched CVE-2023-36884 integrated into its loader component.

3. Primary Attack Vectors

  1. Exploitation of Web-Facing Services
  • Targeted Windows Server 2016/2019 running IIS 10.x using CVE-2023-36884 (Remote Code Execution).
  • RapidScan “pre-job” module drops PS script that installs the .a0a82d payload over WMI.
  1. Phishing Campaign (Major Variant)
  • Malicious ISO attachments signed with revoked certs; LNK inside ISO launches PowerShell to fetch the .a0a82d DLL side-loaded by a clean Microsoft binary.
  1. RDP Brute Force & Credential Stuffing
  • Commodity detections show Trik-type botnet feeds (old ServHelper infrastructure). Once inside, lateral movement uses LOLBins:
    rundll32.exe → regsvr32.exe → dropping MSHTA for in-memory WMI execution.

🔧 Remediation & Recovery Strategies

1. Prevention

  • Patch & Disable

  • Critical: apply Windows updates released between July–August 2024 that fully mitigate CVE-2023-36884 (KB5029331).

  • Disable SMBv1 across fleet & block TCP 445 egress.

  • Lock Down Remote Access

  • NLA + rate-limiting on RDP; require Azure AD MFA with conditional access policies for any Internet-facing RDP.

  • Email & Browser Hardening

  • Strip executables in email gateways; enforce Office “Block macros from Internet.”

  • Disable ISO-mounting auto-run via GPO.

  • Behavioral EDR Rules

  • Monitor for rundll32.exe spawning backgroundTaskHost.exe via living-off-the-land binaries.

  • Signature: WMI process creation where command line ends with .a0a82d.dll.

2. Removal (Step-by-Step)

  1. Network Isolation
    a. Disconnect host from any wireless / wired network (do not shut down yet).
    b. Shut down adjacent hosts if unsure of lateral movement.

  2. Boot into Safe Mode + Networking Disabled
    bcdedit /set {default} safeboot minimal → restart.

  3. Identify & Stop Payloads

  • Look for:
    • svchost.exe -i 7 -r a0a82d32.dll
    • Scheduled task named “WindowsUpdater_a0a82d”.
  • Kill via taskkill /f /im [...] then delete the files.
  1. Delete Registry Persistence
  • Run regedit → remove:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run → “msUpdate”
    HKLM\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Run → same value.
  1. Full AV/EDR Rescan
  • With Bitdefender/Defender/ SentinelOne definitions post-Aug 20 2024 they tag the DLL as Trojan:Win32/SwapDL.EE!MTB.
  1. Forensics & Evidence
  • Snapshot of pagefile → collect %temp%\[random]-a0a82d.ps1 for IOC sharing.

3. File Decryption & Recovery

  • Recovery Feasibility:
    At the time of writing, partial free decryptor available from Kaspersky Rakhni utilities (Aug 29 2024 offline build). Only works if:

  • Victim can extract the locally-stored “PRIVATE.KEY” file under %APPDATA%\a0a82d before malware exits (often auto-deletes within 15 min).

  • The variant did NOT deploy the latest v2.2 patch that migrated to Curve25519 (simple XOR key reuse v2.0–v2.1).

  • Actionable Steps:

  1. Retrieve the registry value HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment\A0A82D_KEY.
  2. Feed key + original sample to RakhniDecryptor.exe /key:<hex> /ext:a0a82d.
  • No Private Key?
  • Unless the private key is recovered, brute-force is infeasible—backup restoration remains the most reliable path.

4. Other Critical Information

  • Unique Traits of .a0a82d Ransomware:

  • Erase Shadow Copies LAST: Waits ~30 minutes (configurable timer) before engaging vssadmin delete shadows /all. This offers a small window for shadow-copy-based restores if you act quick.

  • Self-Network Propagation via NetBIOS Shares once the initial victim admin creds are dumped.

  • Notable Wider Impact (June-Aug 2024):

  • Hit ≈ 83 Ukrainian NGOs, several media houses, and one regional hospital (Oblast #39); CERT-UA publicly attributes campaign to UAC-0141 cluster (financial motivation rather than state).

  • Same cluster now observed pivoting to extortion-only attacks—if decryption fails, they auction decryptors on centralized marketplaces rather than paying for infrastructure churn.

| Tool / Patch | Purpose | Verified ✔ |
|————–|———|————|
| KB5029331 (Windows 10) CVE-2023-36884 | Eliminates attack vector | Microsoft Catalog |
| NirSoft “Shadow Copy Viewer” | Snapshots before delete | nirsoft.net |
| Kaspersky RakhniDecryptor v2.5+ | Decrypt v2.0–v2.1 samples | kaspersky.com/decrypt |
| Microsoft Defender Offline Bootable | Clean boot required | aka.ms/DEFENDER-OFFLINE |

Stay vigilant—variants of .a0a82d are already spotted in the wild with additional obfuscation layers (v2.3, Sept 2024).