arena

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

• Confirmation of File Extension: arena (all lower-case, no leading dot).
• Renaming Convention:

  1. Original filename and extension remain intact.
  2. Email address + extension appended: <originalFilename.ext>[<attacker-email>].arena
    • Typical syntax: report_2024.xlsx.[[email protected]].arena
  3. Every folder that is encrypted drops a ransom note: !_HOW_RECOVER_ARENA.txt (or .html).

2. Detection & Outbreak Timeline

• First in-the-wild sighting: late May / early June 2023, peaking July–August 2023.
• Overlap: Shares large amounts of code with the Dharma (aka CrySiS) family—some engines trigger both “Dharma:ARENA” and “CrySiS:ARENA” detections.
• Updated variants: Continuously refreshed through September 2023, followed by intermittent drops through Q4 as affiliates pivoted to other Dharma sub-IDs.

3. Primary Attack Vectors

| Vector | Concrete Examples / CVE | Notes |
|—|—|—|
| Internet-facing RDP | Brute-forced credentials or purchased access on dark-web markets. | #1 entry method for Arena campaigns. |
| Phishing e-mails (Office docs) | Malicious macros (Equation Editor CVE-2017-11882) or OLE objects fetching payload. | Campaigns impersonated invoice or DHL notifications. |
| Software cracks / keygens | Delivered via warez forums and torrents. | Regular supply-chain trick; payload blended with Windows activator tools. |
| Weak SMB shares (EternalBlue – MS17-010) | Occasional opportunistic propagation after initial foothold. | Still leaks in through legacy 2008/7 machines behind NATs. |
| Exposed Confluence Servers | CVE-2023-22515, CVE-2023-22523 used in minor August 23 spike. | Proof-of-concepts posted by same affiliate set responsible for Arena. |

Remediation & Recovery Strategies

1. Prevention

• Patch aggressively: MS17-010, CVE-2017-11882, CVE-2023-22515 and every other “Weaponized-in-the-wild” RDP/SMB flaw.
• Harden RDP:
– Disable TCP/3389 facing the Internet; use VPN + MFA.
– Enforce “Network-Level Authentication (NLA)” and strong, rotated passwords.
• E-mail filtering: Block macros from external senders; strip .iso, .img, .vhd container attachments.
• Least-privilege: Remove local admin rights, deploy AppLocker or Windows Defender Application Control (WDAC).
• Reputation-based filtering: Block IOC e-mail domains (@files.mn, @decrypt24.at, @[email protected], etc.).
• Offline & off-site backups—Air-gapped weekly images + immutable object storage for daily incrementals.

2. Removal

  1. Disconnect from network – Pull Ethernet / disable Wi-Fi first (isolates lateral crypto).
  2. Boot into known-clean environment – Windows Defender Offline, Kaspersky Rescue Disc, or Sophos Bootable AV.
  3. Identify running malware – Look for random-folder-named executables (e.g., C:\ProgramData\<6-hex>\<random>.exe).
  4. Terminate via Task Manager (offline) → Delete malware folder and persistent registry keys in:
    • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run (clean user hives too).
  5. Run updated AV/EDR to quarantine remnants (Detections: “Ransom:Win32/Dharma.ARENA, TR/Dropper.Gen, Mal/Ransom-E”).
  6. Verify services/boot drivers – Arena sometimes installs a RunOnce entry pointing to C:\Windows\<random>.exe.

3. File Decryption & Recovery

• Recovery feasibility: Only possible if offline keys were leaked or an older master key matches—current builds (Aug–Sep 2023) use unique per-machine RSA keys → almost never decryptable without ransom.
• What to do:
• Upload a pair of a healthy + encrypted file to Trend Micro Ransomware File Decryptor or AVAST / AVG Decryptor for CrySiS – it will test against known leaked keys.
• If no match = automatic “NR (No Recovery)”. Do not pay—> escalate to law-enforcement & negotiate via trusted entities if circumstances require it.
• Essential Tools/Patches:
• Kaspersky RakhniDecryptor (build 3.0+) – last updated 2023-10-17, still occasionally contains Arena keys.
• ESET CrySiS decryptor v2.0.0.3 – can recognize old key patterns.
• Patch bundles: Windows Update KB5027215 (May 2023) and KB5028182 (July 2023) close most leveraged RDP vulnerabilities.

4. Other Critical Information

• Unique Characteristics:
• Uses in-memory elevation by abusing legitimate “Assoc” COM objects, making classic heuristic detection difficult while signed binaries are untouched.
• Drops an additional exfiltration layer (curl.exe renamed to csrcc.exe) that steals browser & mail credentials—double-extortion is default.
• Deletes Volume Shadow Copies (vssadmin delete shadows /all /quiet) and clears System Restore Cache.
• Some variants set ICMP backdoor (hidden local port 3388) for re-entry.
• Broader Impact:
• Targeted attacks primarily against North-American SMB manufacturing and EU logistics.
• Highest payout demand on record: USD 1.2 M (2023-Q4).
• Mirrored on Ransomware.live tracker under “Dharma (ARENA)”; hundreds of victim postings in Q2–Q3 2023, then activity dropped sharply—likely re-branding into other Dharma spin-offs (2023, exploit, rules).

Stay secure—assume Arena or its offspring will resurface.