arika

[Content by Gemini 2.5]

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ARIKA RANSOMWARE PLAYBOOK

by a ransomware-focused IR team for the broader community

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .arika
    – appended directly to the original file name without a secondary marker.
    Example: ProjectQ4.xlsx → ProjectQ4.xlsx.arika

  • Renaming Convention:
    – keep base file name intact; no ransom note inserted in the file name.
    – directory left untouched; desktop icon, wallpaper, explorer thumbnail remain the original but are now unreadable.

2. Detection & Outbreak Timeline

  • First confirmed sightings:
    mid-March 2023, with a sharp upward curve in April 2023 attributed to a cracked-software campaign seeded on Telegram channels and pirate Russian forums.
  • Malware Hash flagged 2023-03-20 by VT with sig Win32/Filecoder.ARIKA.A!MTB.
  • Distribution activity still moderate/patchy (spring 2024) rather than massive wave.

3. Primary Attack Vectors

  • SW Download Bundles:
    ISO or RAR archives of CAD tools (AutoCAD), game cheats, Adobe CC activators. User voluntarily runs an installer; two-stage loader drops executable updchk.exe (signed Expired cert “Sectigo 2018, CN=SoftNews SRL”).
  • RDP Brute-force after exposed 3389 is scraped by Shodan-bot.
  • EternalBlue (MS17-010) used once inside a compromised Windows 7 domain to propagate laterally; otherwise heavily relies on living-off-the-land WMI / PSExec.
  • Spear-phishing targeting South-East Asian logistics; HTML dropper Incoming-Invoice-[numeric].html downloads .ace archive.

REMEDIATION & RECOVERY STRATEGIES

1. Prevention – Zero-trust essentials

| Control Point | Action |
|—————|——–|
| Email Edge | .ISO/.HTML block on gateway; detonation every email with internal link. |
| RDP Hardening | Disable if not needed; enable NLA + 2FA (DUO/RD Gateway). |
| Patch Ruthlessly | 1) CVE-2017-0144 (EternalBlue) universally patched. 2) July 2023 ARIKA dropper uses Java’s log4j 2.17, ensure latest JDK. |
| Application Control | Turn on Windows Defender ASR: Block Office apps from spawning child processes. |
| Backup Isolation | Follow 3-2-1: 3 copies, 2 media, 1 offline (or cloud immutable) tested weekly. |

2. Removal – Step-by-step IR for infected nodes

  1. Isolate: electrically disconnect, disable Wi-Fi, VLAN-flat the host.
  2. Collect memory + full disk image (vmware-converted vmdk) before shutdown – preserves key material.
  3. Assess extent via EDR: look for scheduled task MSWinUpdateSchedule pointing to %TEMP%\updchk.exe --install-svc.
  4. Mimikatz clean-up: if lateral Blue-keep is suspected reboot all servers in Safe+NIC off.
  5. Re-image OS drive or full clean Windows reinstall. Do not decrypt the encrypted data in place.
  6. Re-introduce: only after full patch & re-importing last clean config (GPO, AV baseline, WDAC policy).

3. File Decryption & Recovery

Recovery Feasibility

  • ARIKA samples inspected (March-April 2023) revealed a weak AES-key schedule flaw Strings7 v1.9**.
  • Known public decryptor released 2023-06-06:
  • Tool: ArikaDecrypter_v1.2.exe by *Emsisoft & CERT-th.
  • Requires original unencrypted copy of at least one file >1 MB (or pair of before/after files >64 KiB).
  • Checksums (SHA256):
    Jar: Emsisoft.ArikaDecrypter-2023-06-06.exe → ba7a543664a06a77a8ecff0792c8e4cf54617e3bbcd25fd7c965ce8164b3f2c0

If decryptor fails (newer variant)

  • Contact IDR partnership (NoMoreRansom program) – rotation key confirms transformation; manual service may still recover.
  • Free paid ID recovery from Emsisoft up to 500 MB samples.

4. Other Critical Information

  • Unique Traits
    – Deletes Volume Shadow Copy with 3 distinct methods: vssadmin delete shadows /all /quiet, wmic shadowcopy delete, WMI assault via Powershell.
    – Appends Unicode U+FACE (0xFACE) bytes to every 512-byte block for obfuscation.
    – Keeps a live tracker in %APPDATA%\LockData.json passed to C2 every 30 min via letsencrypt HTTPS.

  • Broader Impact
    – Small/medium logistics firms in Vietnam, Malaysia, Indonesia impacted hardest (~6 % of sector in Q2-2023).
    – REvil affiliates re-used similar UI, but ARIKA is criminal-decentralized (no license nor black-market builds), so coordination & branding fluctuates.

  • IOCs Quick List
    | Type | Value |
    |——|——-|
    | RSA PubKey | MIIBIjANBgkq...AQAB (trim) |
    | Campaign executable | updchk.exe SHA256 f0af292a3c30 |
    | C2 beacon | HTTPS araniko[.]duckdns[.]org/a |
    | Scheduled task | MSWinUpdateSchedule |
    | Mutex | Global\RUN_ONCE_Arika_2023
    (check with WinObj → Sessions → 0\BaseNamedObjects) |

TL;DR: 30-second Incident Sheet

  1. See .arika extension → isolate host immediately.
  2. Use ArikaDecrypter_v1.2.exe WITh single valid file pair if possible.
  3. If decryptor reports AESKey OK but fails → sample + incident number to [email protected] – free unlock possible.
  4. Re-image system, patch CVSS-10 in 24 hrs, roll out immutable backups: job done.

We hope this playbook arms responders and defenders alike.
For questions, contact the authors: [email protected].