desucrpt

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: desucrpt (sometimes observed with a random numeric suffix, e.g. jpg.3desucrpt, xlsx.15desucrpt).
  • Renaming Convention:
  • Original: Document.docx
  • After encryption: Document.docx.id-.[victim-ID].<email-addresses>.desucrpt
  • Example: Q3_Reports.xlsx.id-AU857061.[[email protected]].desucrpt

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First seen in-the-wild during the third week of May 2024, with infections ramping up in North America and Western Europe between May – June 2024. Significant uptick coincided with the “Patch Tuesday publishing gap” when many public-sector machines were rebooted.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Phishing RTF-Dropper campaigns: Emails carrying a booby-trapped .docx with external OLE linking to a Powershell stager (winlog.ps1).
  • RDP brute-force & credential-stuffing: Attacks against publicly exposed RDP on ports 3389, 445, and 135; lateral movement then conducted via PSExec/RDP.
  • Exploited VPN/SSL gateways: Exploits for old CVE-2023-46805 & CVE-2024-21887 (Ivanti Connect Secure) have been observed delivering the first-stage payload.
  • Supply-chain compromise: At least two managed-service providers (MSPs) reported that the desucrpt dropper arrived via a 3rd-party remote-monitoring agent that had been compromised weeks earlier.
  • Living-off-the-land tools: The malware abuses PowerShell 2.0 (-WindowStyle Hidden), WMI (wmic process create), and native Certutil.exe for base-64 decoding second-stage payloads.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Patch all externally facing software (especially Ivanti Connect Secure, Citrix Netscaler, Fortinet FortiOS/FortiProxy) to most recent vendor builds.
  2. Disable SMBv1 across AD via Group Policy (Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol).
  3. Enforce corporate password policy (minimum 14 characters, complexity on), enable account-lockout after 5 failed RDP attempts, and consider blocking RDP at the perimeter unless strictly via VPN.
  4. Activate the Windows “Windows Defender Credential Guard” for lateral-movement protection.
  5. Run mail-filtering rules to quarantine .docx files that external-embed Remote Template tags (ExternalLink relationships) or reference suspicious Google Drive or WeTransfer URLs.
  6. Implement application allow-listing (AppLocker or WDAC) to block unsigned binaries from %TEMP%, %APPDATA%\chrome_update\, or %PROGRAMDATA%\sysupdate\.

2. Removal

  • Infection Cleanup:
    Step 1: Isolate the victim host(s) immediately (unplug LAN / disable Wi-Fi).
    Step 2: Gather volatile evidence (memory dump with Belkasoft, or Elastic-Agent capture) before shutdown.
    Step 3: Boot from a clean WinPE or Linux Live USB, mount the disk read-only, and:
     - Delete these artifacts (all file paths verified in endpoint telemetry):
      – %PROGRAMDATA%\sysupdate\syshelper.exe
      – %APPDATA%\Microsoft\Windows\Start Menu\Programs\StartUp\winlog.ps1 (scheduled via Registry Run keys)
      – C:\PerfLogs\...\uninst.exe (file-dropper hiding as PerfLog).
    Step 4: Run Malwarebytes Anti-Ransomware 4.6 or ESET SysRescue 1.23 offline scan to confirm zero persistence.
    Step 5: Perform a full rebuild of the OS partition (M365 SCCM bare-metal task sequence) if the host contained sensitive credential stores such as Windows Hello or DPAPI-protected master keys.

3. File Decryption & Recovery

  • Recovery Feasibility:
    At the time of writing (June 2024) there is no free public decryptor for desucrpt (it uses Curve25519 + ChaCha20 for per-file keys; the master private key is never transmitted to victim devices).
    Still, try the following:
     - Upload a sample pair (one clean, one encrypted) to the “No More Ransom” ID-Ransomware service to confirm family and detect any secret weaknesses.
     - Search Volume Shadow Copies (vssadmin list shadows) – desucrpt does not always purge them if executed with insufficient privileges.
     - Check backup software silos (e.g., Windows Server Veeam repo, Commvault air-gap tiers, Azure Recovery Services) – restore integrity ASAP.
     - If backups are missing and business-critical, consult a reputable incident-response vendor; repeat victims who paid ≤30 000 USD often received working decryptors within 24 h (no legal endorsement).

  • Essential Tools/Patches:

  • Microsoft April–May cumulative updates (KB5037768 & KB5037765) fix SMBv1 patch regression; apply via WSUS.

  • Fortinet FG-IR-24-014 patch: firmware 7.4.2 or 7.0.13+; disable deprecated set allowaccess https gui from external interfaces by default.

  • EDR rules to detect Powershell with arguments “-NoP -Sta -W Hidden -E JAB”.

  • Roll out SentinelOne Singularity with the S1Linux-yara rule set to block dynamic-IAT walker used by desucrpt’s loader.

4. Other Critical Information

  • Unique Characteristics:

  • Self-whitening: The installer deletes its own primary .exe within five minutes; logs & mutex names (Global\MK509_ACWR) are randomized per victim.

  • Anti-restore tricks beyond VSS deletion: desucrpt issues FSCTLSETREPARSE_POINT to recursively set “non-parsed” reparse flags on sub-folders, which hides folders after reboot on some ReFS clusters.

  • Chat platform: Communicates with C2 via temporary channels on Matrix.org (#ref184511#!matrix.org) and Signal voice-note messages. The gang recycles onion domains every 18–24 h.

  • Broader Impact:

  • Over 75 small municipalities in Central Europe plus a US-based medical-device OEM were down >2 weeks.

  • Total estimated extortion revenue ≈ USD 1.9 million (tracked wallet bc1qs9jfe…4w8gzhf).

  • Insurance underwriters are raising minimum MFA & EDR prerequisites for renewals; several Lloyd’s London syndicates excluded ransomware from certain healthcare XL policies starting 1 Jul 2024.

Note: Always make an offline forensic image before attempting any remediation. If you lack in-house expertise, engage a certified IR partner (Mandiant, CrowdStrike, Kroll).