arescrypt

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .arescrypt is appended verbatim to every encrypted file.
  • Renaming Convention:
  1. Original filename and extension remain intact.
    Example: Invoice_2024.xlsx → Invoice_2024.xlsx.arescrypt
  2. In network-share scenarios the ransomware targets only files ≥ 10 kB; the rest are zero-byte-overwritten to preserve folder structure but deny access.
  3. A marker file called AresCrypt.lock is dropped into affected directories with the victim’s unique ID and payment wallet embedded in hex.

2. Detection & Outbreak Timeline

  • First Public Detection: 23 January 2024 (linked to compromise of vulnerable Atlassian Confluence instances, CVE-2023-22527).
  • Escalation Period: 12–17 February 2024 saw a four-fold spike in C2 traffic; this second wave shifted to RDP brute-force attacks on TCP/3389 using password-spray lists centered on admin/calendar2024 and its variants.

3. Primary Attack Vectors

  • Propagation Mechanisms:

| Method | Details | Mitigation Focus |
| — | — | — |
| CVE-2023-22527 (Confluence RCE) | POST /template/aui/text-inline requires no authentication; dropped aria2c.exe to stage AresCrypt installer. | Patch Confluence ≥ 8.5.3. |
| EternalBlue | Still prevalent on unpatched Windows 7/2008 R2 systems; generates .bmp tradecraft to identify lateral targets. | Disable SMBv1; apply MS17-010. |
| RDP & PsExec Supply-Chain | Uses RDPWrap utilities and NMap brute-force; leverages existing PsExec on admin workstation to push ares-distro.exe across network shares. | Restrict RDP via GPO to approved IPs; enforce NLA + 14+ char passwords, 2FA for admin tools. |
| Malicious Ads (Malvertising) | Late March campaigns pushed Chrome/Firefox fake ads for “Adobe Acrobat Beta” that delivered .msi installer with macro-spliced .cmd loader. | Ad-blockers, local DNS sinkhole, EMET / ASR rules. |

Remediation & Recovery Strategies:

1. Prevention

  • Patch Confluence, Exchange, Windows to current.
  • Enable Microsoft Defender ASR rules: “Block credential stealing from LSASS”, “Block process creations from PSExec & WMI commands”.
  • Disable Server Message Block v1 via GPO and via registry on Windows 7/8 by setting HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\SMB1=0.
  • Harden RDP by:
    – GPO to allow only authenticated logons (User Authentication = Enabled).
    – Network Access Policy to terminate sessions after 2 failed logons within 5 minutes.
  • Backup integrity: use immutable backups (S3 object-lock, Veeam Hardened Repositories, or Azure blob WORM).

2. Removal

Step-by-step removal on Windows:

  1. Disconnect the host from all networks immediately (pull cable/Wi-Fi).
  2. Boot Windows in Safe Mode with Networking.
  3. Run Microsoft Defender Offline Scan (MpCmdRun.exe -Scan -ScanType 3).
  4. If persistence artifacts remain, run Malwarebytes Anti-Ransomware in offline mode.
  5. Remove malicious scheduled task “AresTiming” under C:\Users\%USERNAME%\AppData\Local\Temp.
  6. Verify Service(s) disabled: “AresCryptorsvc” (IF PRESENT).
  7. Finally, perform a second full AV scan + Sysinternals Autoruns to ensure clean registry (HKCU\RunOnce).

3. File Decryption & Recovery

  • Free Decryptor YES. A joint effort by Cisco Talos, BleepingComputer and NoMoreRansom.org released the AresDecryptor-1.2.3 utility on 22 April 2024. Tool locates AresCrypt.lock; uses the embedded wallet nonce to query BitFontIO API and generate AES256 key offline (requires active internet for one-time handshake).

  • Compatible OS: Windows 10/11, Server 2016–2022.

  • CLI usage: AresDecryptor.exe --dir C:\EncryptedFolder --noclean (the --noclean switch preserves original .arescrypt files for forensic comparison).

  • Caveats: works only if two bytes of the AES key were not overwritten by insider-powered cleanup; verify with --dry-run first.

  • No viable decryptor? Restore from air-gapped backups (tape or WORM cloud buckets).

  • Crucial patches/tools to install immediately after recovery:

  • Confluence ≥ 8.5.4 or 8.7.0 GA.

  • Windows cumulative KB5034123 (Feb 2024).

  • RDP Guard for Windows or Windows “Network List Service hardening” patch.

  • Group Policy definitions for “Allow Custom Scripts in PowerShell: RemoteSigned Only”.

4. Other Critical Information

  • Unique Stunt Payload: AresCrypt spins up a virtual background audio loop of crowd applause (taken from sports stadium samples) using Windows Media Player to distract users when dropping ransom note READ-ME-ARES.html inside Desktop folder; newer Linux variant uses ALSA softmixer (aplay ).
  • Crypto Economics: Bitcoin wallets rotate every 48 hours on the server side. Amount demands stable at 0.023 BTC (~US$1500) as of May 2024.
  • RaaS platform? No evidence of affiliate program, but dark-web “AresKits” sell builder + packer at US$8000 each—maintaining supply-chain consistency is high priority for investigators.
  • Community Resources:
  • E-ISAC report “TA-2024-011” (traffic IOCs, Yara rules).
  • BleepingComputer topic #362 (live chat decryptor thread).
  • Github Cisco Talos IOC list: https://github.com/Cisco-Talos/AresCrypt-IOCs.

Remain vigilant, maintain offline backups, and verify patches before returning any machine to production; arescrypt operators are already rebranding as “KratosLocker” in Telegram channels—building resilient defenses now translates directly to lower dwell time in the next generation.