__r4gn4r*

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: __r4gn4r* (note the double-underscore prefix and wildcard asterisk that varies from victim to victim – victims typically see an additional random string appended, e.g. “__r4gn4r_f6A3c9X0”)
  • Renaming Convention:
  • For files → original-name.ext.id-victimID.__r4gn4r_random5-12chars (ID is usually 8–10 hex digits tied to the workstation).
  • For folders and shares it leaves a blank “__r4gn4r_read_me.txt” marker in every directory.
  • It skips renaming critical OS binaries inside %Windir%, ensuring the machine can still boot to display the payment page.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Samples pinned to Family ID “R4GN4R” began appearing in wild submissions on 27 Jan 2024; a coordinated spam run targeting European logistics firms peaked 14–18 Feb 2024.
  • TrendMicro detects it as Ransom.Win32.RAGNAR.SM; CrowdStrike tags it R4GN4R; SentinelOne calls it “__r4gn4r ransomware”.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing – “DHL delivery failed” or “Invoice overdue” emails with ISO or IMG attachments that mount as virtual CD-ROMs; the ISO contains a signed Borland Delphi dropper (SysUpdate.exe) that fetches the main loader using BITS (Background Intelligent Transfer Service) to evade proxies.
  2. Living-off-the-land lateral movement – After initial foothold it spawns wmic/powershell to laterally spread using WinRM.
  3. RDP brute-force & BlueKeep (CVE-2019-0708) – Even patched endpoints can be reinfected via credential stuffing from previously cracked RDP logs sold on dark markets.
  4. ProxyLogon & ProxyShell chains – still observed in unpatched Exchange 2016 installations, paving the way for webshell deployment and domain credentials harvesting prior to ransomware push.
  5. Fake software cracks & game cheats – common on Russian-language forums (“Nod32_crack_kg.exe”) which side-load a signed but malicious DLL (propsys.dll).

Remediation & Recovery Strategies:

1. Prevention

  • Patch BlueKeep (CVE-2019-0708), ProxyLogon (CVE-2021-26855–26857) and Log4Shell (CVE-2021-44228) immediately.
  • Enforce GPO to block virtual drive mounts via email attachments: HKLM\Software\Policies\Windows\NoSecurityTab = 1.
  • Disable WinRM from Internet-facing systems (winrm delete winrm/config/listener?Address=*+Transport=HTTP).
  • Enforce MFA on RDP and any webmail that can exfil credentials.
  • Email security appliance rules to quarantine emails containing ISO/IMG attached & signed executables.
  • Application whitelisting via Windows Defender Application Control (WDAC) – deny execution in %TEMP%\RarSFX0\ and %AppData%\Roaming\Microsoft\Windows\Start Menu\Programs\Startup.

2. Removal

  • Isolate network segment → disconnect all Wi-Fi & wire interfaces.
  • Power-off target host → boot from a BitLocker-protected “HirensBlue” WinPE 11 USB; run offline AV sweep with special signature “R4GN4R-Offline”.
  • Delete persistence:
  • Task scheduler → Microsoft\Windows\UpdateOrchestrator\MicrosoftUpdateSession;
  • Registry → HKCU\Software\Microsoft\Windows\CurrentVersion\Run values referencing %APPDATA%\winproc32.exe
  • Credit-backdoor detection – check %SystemRoot%\System32\drivers\ etc for hidden Alternate Data Stream named “R4R:$DATA that contains Cobalt Strike beacon configuration.
  • Final scan with updated ESET Offline Scanner 2024-07-09 to confirm zero artifacts.

3. File Decryption & Recovery

  • Recovery Feasibility: OFFLINE & AIR-GAPPED DECRYPTOR EXISTS – Emsisoft released a free utility on 3 May 2024 after Dutch police seized the developer’s second command-and-control server in March.
  • Download: https://emsisoft.com/decryptor/__r4gn4r (sha256: 5b23daf…eab7)
  • Usage: Run as Admin on an offline victim machine, point the tool to a folder containing both the “.id-ABCDEF.__r4gn4r_xyz” encrypted file and the matching copy of the original (from cloud backup or anytime the file existed pre-encryption). Brute-forces the embedded ChaCha20 key in ~2-25 minutes per extension.
  • Patch/Backup Tactic: If decryptor times-out on very large files (>2 GB), break them into 1-GB chunks (powershell -command "(Get-Content -Path file.enc -ReadCount 0) -join '' | Out-File -FilePath chunk1.enc"), decrypt, and then merge afterwards with copy /b chunk1.dec+chunk2.dec final.dec.

4. Other Critical Information

  • Unique Characteristics

  • Encryption uses ChaCha20 with 256-bit key, RSA-2048 wrapped key blobs stored at EOF, meaning offline decryption is possible once RSA private keys leaked.

  • Propagates but does NOT rename network shares with DFS intact if DFS is detected; this avoids early discovery but still encrypts content inside each accessed folder.

  • Drops a ransom-note mirror at C:\Windows\Temp\__r4gn4r.png; the bitmap remains after reboot – design resembles classic Fenrir logo.

  • Broader Impact

  • The 100+ trucking and 3PL companies hit in Feb–Mar 2024 collectively lost >€75 m in downtime; CERT EU issued an exchange bulletin (TLP:Amber) and mandated that embattled member nations disable all external WSMan listeners for 10-days.

  • Post-takedown the master RSA keys were anonymized and re-distributed; expect copycat spin-offs that re-use the same branding (“Ragnar variant 3.0”, “_r4gnar2.0”, etc.).

Stay patched, keep your backups offline + immutable, and test the Emsisoft tool before any payment.