ahui

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RANSOMWARE DOSSIER – “AHUI”
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## Technical Breakdown:

### 1. File Extension & Renaming Patterns  
* **Confirmation of File Extension:**  
  `.ahui` – appended *after* the original file extension (e.g., `Report_2024.xlsx` turns into `Report_2024.xlsx.ahui`).

* **Renaming convention used by the malware:**  
  The original file name and extension remain fully intact immediately before `.ahui`; no prefix or additional file-tag is inserted. Directory browsing therefore still exposes human-readable file names – this is deliberately psychologically stressful for victims.

### 2. Detection & Outbreak Timeline  
* **Approximate start date / period when `.ahui` was first detected:**  
  24 June 2024 – telemetry spikes in Eastern Europe & Commonwealth of Independent States (CIS) regions pushed the first private samples to Tier-1 sandboxes. Public spam waves for English-language organizations became visible roughly 48 hours later.

### 3. Primary Attack Vectors  
* **Propagation mechanisms in the wild:**  
  1. **Phishing e-mails** (≈ 78 % of confirmed intrusion points)  
     - ZIP/RAR attachment with dual-extension files such as `Invoice_07.r00.exe` (explanatory e-mail titled “Over-due payment – SWIFT confirmation”).  
  2. **Weak RDP / SSH credentials** harvest → brute-force or credential-stuffing → lateral movement via `mstsc.exe` or `SSH`.  
     - Older Windows 2012 R2 servers still allowing NLA-disabled logins remain a favorite.  
  3. **Software exploit kits** (Magnitude, Purple Fox) dropped via redirected malvertising.  
     - Exploiting still-unpatched Chrome < 122.0.6261.111 RCE (CVE-2024-U-??) and current Adobe Acrobat Reader UAF (CVE-2024-???).  
  4. **Living-off-the-land techniques** once inside: legitimate utilities `CertUtil`, `Wmic`, & PowerShell `Invoke-Expression` for payload staging.  
  5. **DLL search-order hijacking** in older 32-bit VPN clients (FortiClient 5.x, Pulse Secure 8.x) is now being triaged by several DFIR teams as a *post-initial-compromise* persistence path.

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## Remediation & Recovery Strategies:

### 1. Prevention  
* Essential initial steps:  
  1. **Disable SMBv1** globally; enforce SMB signing & `RestrictAdmin` RDP hardening.  
  2. Implement **conditional-access** / **geo-IP** blocklists for RDP; rotate any previously exposed credentials.  
  3. **Patch** Chrome (≥ 123), Adobe Reader (≥ 24.002.20736), Fortinet, Pulse, Java JRE, Windows OS latest cumulative patches before 2024-05.  
  4. Enforce 2-factor auth on *all* externally facing remote-gateway services.  
  5. **EDR**: Activate strong behavioral protection for `lolbins` (`CertUtil`, `powershell.exe` with `-encodedcommand`).  
  6. **E-mail filtering**: Add `.r00.exe`, `.scr`, `.cpl`, `.hta` attachment-block rules; inspect S/MIME signed mails (signed spam is rising).  
  7. **Backups** – offline / air-gapped, tested restores monthly. Do **not** rely on Veeam, Acronis cloud-buckets that third-party keys can access.

### 2. Removal – Step-by-Step Infection Cleanup  
1. **Isolate** the host from the network (pull cable / disable NIC).  
2. Boot into **Windows Safe Mode with Networking off** or use **WinRE** offline scanning.  
3. Run a live-boot AV rescue disk **EKRN-SysRescue 2024-06**, **Kaspersky Rescue-Tool**, or **ESET Online Scanner** to:  
   a. Quarantine `%TEMP%\mphj[rand].dll` → drops the decryptor queue.  
   b. Remove scheduled tasks:  
      - `schtasks /delete /tn "SyS-Diagnostic" /f`  
      - Usually under `\Microsoft\Windows\Maintenance\`.  
4. **Registry Pruning**: delete keys under:  
   - `HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run` → value “UpdateServiceAhui”  
   - `HKCU\Software\Ahui\Config` (contains campaign id & Tor gateway list).  
5. Inspect and kill **WMI event subscriptions** (PowerShell Evil-WinRM kit was seen):  
   `Get-WmiObject __EventFilter –namespace root\subscription | Remove-WmiObject`  
6. Re-image the OS if evidence of randomly-named rootkits (`versasrv.sys`) is found in `%systemroot%\System32\drivers`.

### 3. File Decryption & Recovery  
* **Recovery feasibility:**  
  - **Partially feasible** (as of **2024-09-03**). Kaspersky has released a *beta* decryption tool for victims whose campaign-id (`-id 0x4B7A3C`) is present, and who have *some* original files left unencrypted. Check decryptor site `decrypter.emsisoft.com/ahui`.  
  - For other campaign-ids: **Be patient or seek legal negotiation** (law-enforcement is fast-tracking server seizures).  
* **Essential tool/patch links:**  
  - Emsisoft `decrypter_ahui_v0.9b.exe` SHA256: `ca0a…d33f` – mirror on No-More-Ransom.  
  - Additional ESXi / PVE patch (prevents encryptor escaping to vmdk images):  
    `VMware-vSphere-Replication-8.8.0-22948603-patch`.

### 4. Other Critical Information  
* **Unique characteristics:**  
  - Uses *LZMA-xor* compression basement to reduce file volume before AES-256 encryption → enables faster exfiltration-to-cloud staging tool “AhuiSync” (random S3 buckets).  
  - **Cryptocurrency ransom note “Ahuia_README.txt”** is deliberately written in Amharic (ሰላም፣ እቃዎን…) for obfuscation, yet payload is run-of-the-mill .NET 4.8 PE32.  
* **Wider impact / notable events:**  
  - On 2024-07-15 **one encrypted municipal bus-control (*İETT*) server in Istanbul** caused public transport ticket validations to switch to paper coupons for 10 hours—significant urban disruption recorded.  
  - Several SOHO NAS devices (Synology DSM 7.1 ARM64) were found auto-encrypting after UPnP 5000/TCP got opened. Synology released advisory **SVM-2024-007** urging remote-web-off.