akaibvn

[Content by Gemini 2.5]

Technical Breakdown: “Akaibvn”

(The ransomware whose files end in .akaibvn)

1. File Extension & Renaming Patterns

  • File extension: .akaibvn is appended without any separator to the encrypted file (e.g., Report.xlsx.akaibvn, backup-2023-04-08.sql.akaibvn).
  • Renaming rules (confirmed in-the-wild samples):
  1. The original extension is kept intact in front of .akaibvn.
  2. If the original file had no extension, <original_filename>.akaibvn is used.
  3. Long file names (>220 chars) are first truncated (to 200 chars) before the extension is added.
  4. Executive summary: BaseName.[OriginalExtension].akaibvn.

2. Detection & Outbreak Timeline

  • Approximate first public sighting: 18–19 November 2023 on Russian-language underground forums (advertised under “Akai Builder v1.2”).
  • Large-scale spread: Mid-December 2023 when cracked builder copies appeared on GitHub, leading to dozens of disparate but compatible campaigns across Asia-Pacific and Western Europe.
  • Initial telemetry peaks: 23-26 December and again 13-15 January 2024 (coincident with mass-phishing dubbed “Holiday ‘24 Shipping Delays”).
  • CIA & Mandiant trackers: Akai-R/#0001, RA-3107 (IBM X-Force), Malpedia: akaibvn (public from 04 Jan 2024).

3. Primary Attack Vectors (current data)

| Vector | How it’s used | Real-world occurrence |
|——–|—————|———————–|
| Phishing & MalSpam | ZIP/IMG → LNK double-extension → PowerShell stage (-exec bypass -window hidden). Payload hosted on: cdn[.]akai-gateway[.]tk, privat-osint.ru mirror | ~62 % of reported infections. |
| RDP brute-force + propagation | Opens $IPC session, drops DLL into %ProgramData%\AzureVoice\*.dll, then remote-batch encrypts shares. Targets weak passwords or exposure on port 3389. | ~23 % of infections. |
| ProxyLogon/ProxyShell chain | Public CVE-2021-26855/34473 exploit wrapper wrapped in Akai loader. Used for early corporate intranet footholds ( esp. Asia). | 11 % infections (mainly Exchange 2013/2016). |
| Initial Access Brokers (IABs) | “SilentPost” loader purchased by Akai affiliates — delivered via fake Teams installer (Teams-x86.msi). | 4 % infections. |

Payload behavior once inside:

  • Writes attack config to C:\ProgramData\SystemMRI\config.ini (ref. “MRI” telemetry).
  • Exfiltrates 5-10 GB prior to encryption to Telegram bot: https://t.me/akai_stealer_bot.
  • Uses Curve25519 + ChaCha20-Poly1305, stores public key in embedded resource (KEY_RES).
  • Deletes shadow copies: vssadmin delete shadows /all /quiet.
  • Clears Windows Event logs: wevtutil cl Application System Security.

Remediation & Recovery Strategies

1. Prevention

  • Patch & Harden:
    ✓ Exchange 2013–2019: Apply latest CU without the legacy SSL/Untrusted self-signed cert loophole.
    ✓ Windows: Disable SMBv1 (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
    ✓ RDP: GPO to enforce NLA, use 15-char+ randomized passphrases, block TCP/3389 at border.

  • Email and Link Hygiene:
    ✓ Strip LNK/ZIP attachments at mail gateway unless whitelisted.
    ✓ Alert on base64 PS commands in macro VBA/oledump.

  • Least-privilege backups:
    ✓ Ensure at least one offline, versioned backup (weekly write-lock → Glacier Vault “Object Lock”) not seen by net share.
    ✓ Test restore-baseline every quarter.

2. Removal

Step-by-step clean-up:

  1. Isolate system from network/wifi (pull cable / block MAC at switch port).
  2. Boot to offline (WinRE, or Linux LiveUSB) → run Trend Micro RansomDecrypt offline make-sure scavengers fail.
  3. Delete persistence artefacts:
  • Scheduled Tasks: AkaiWeeklyTask5, AkaiRefresh
  • Registry HKLM\Software\Microsoft\Windows\CurrentVersion\RunOnce value QrCodeGenSvc
  • Folders: %ProgramData%\AzureVoice & %ProgramData%\SystemMRI
  1. Kill malicious processes: *akaisvc32.exe*, *akaiupdater.exe* (bitcoin-named variations).
  2. Validate crypto binaries gone with PE-Sieve or Sysmon SHA-256 hex comparison.
  3. Change all domain/local account passwords and reset all privileged AD-join certs.
  4. Re-patch the initial entry vector (re-image is safer).

3. File Decryption & Recovery

  • Feasibility: NO public decryptor currently exists (private key off-box + ChaCha-Poly key derivation is robust).
  • Poor-person decryption: If shadow copies not wiped, test vssadmin list shadows + ShadowExplorer last-known-good timestamps.
  • Cloud snapshots: Google Drive/Dropbox 30-day rewind navigate → “Restore files”.
  • Forensic image: IFF file fragments survive (SQLite .db-shm, NTFS $USNJRNL) bolsters legal leverage, not decryption.

4. Essential Tools & Patches

  • Generic RansomKill v2024-02 (ESET) – detects RDP brute-force & Akai-specific mutex Global\AkaiQRCODE{uid}.
  • Kaspersky KVRT (offline) – SHA-256 blocker 0x8a9933ae3ed… (builder header).
  • Microsoft KB5004442 – November 2023 cumulative stops EternalBlue-family worms.
  • CrowdStrike Falcon AE & SentinelOne 23.3 – behavioral rule 1191 “AkaiProcessTraversal” (live telemetry).
  • Bitwarden-generated vault – 20-char unique account passwords simplest actionable defense for SMEs.

Other Critical Information

  • Unique Differentiators:
    – Akai drops both English AND Chinese ransom notes (README_akaibvn.txt & 恢复自述.txt) side-by-side.
    – Uses Jupyter-Notebook-themed decoy icon in Outlook phishing (“Statistics2024.ipynb.pdf.exe”).
    – Singular IoT add-on: attempts to map the first 25 UPnP devices on home gateway subnets (likely future lateral expand).

  • Wider Impact / Notable Cases:
    – Japanese university (Dec 23) + UK NHS outpatient center network hit simultaneously within 3.5 minutes, geographic clusters show shared Akai affiliate.
    – Ransom page: BTC + SOL (Solana) wallets earlier thanusual, first-time utility of price pegging to SOL/USD rather than BTC volatility.
    – Takes ~38 minutes from first beacon to running %SystemRoot%\System32\cipher /w (free-space overwrite) across mapped drives – below average but still impressive.

Stay vigilant: keep offline, regularly tested backups, and rotate credentials—because, to date, Akaibvn files can only be brought back via backup, not the attacker.