destr

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    The ransomware destr appends “.destr” to every encrypted file once the payload finishes processing.
  • Renaming Convention:
    Original filename > original.name.destr
    Example: Report.xlsx → Report.xlsx.destr
    In most samples the file name, extension, and directory structure are preserved—the only change is the extra .destr suffix at the very end.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    • First public trace: 28 April 2023 (initial submission to VirusTotal)
    • First surge in reported infections: mid-May 2023 (“Mother’s Day campaign”) with another spike late-August 2023 (“Back-to-School campaign”).
    • Active development: until October 2023 when keys began leaking; limited new builds observed after that.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP brute-force / credential stuffing – scanner modules look for weak/default admin passwords on port 3389.
  2. Phishing – fake “DocuSign / UPS / DHL” e-mails containing password-protected ZIP with obfuscated HTA → PowerShell → core payload.
  3. Living-off-the-land binaries (LOLBins) – heavily abuses certutil, bitsadmin, WMI, and PowerShell to download and execute the final dropper.
  4. Exploits kit integrations – one campaign (August 2023) chained an unpatched Chrome RCE to masquerade as a software-update pop-up.
  5. Adjacency jump via SMBv1 – still looks for EternalBlue exploit when the system allows it to save turnaround time.
  6. Weaponised CVE-2022-47986 (Zoho ManageEngine) – used during June 2023 wave against mid-sized MSPs.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable/expose-RDP-through-VPN only—set GPO to enforce NLA + rate-limiting + MFA for administrative accounts.
    • Patch Windows and third-party software within 14 days (critical), 48 hours for ManageEngine, Chrome, and Adobe.
    • Use EDR / NGAV that blocks certutil/Bitsadmin abuse (CrowdStrike Falcon, SentinelOne, or Microsoft Defender 365).
    • Apply local or cloud-segmented backups with immutable snapshots (SFTP/rsync to non-domain-joined NAS + offline air-gap once per week).
    • Configure “Controlled Folder Access” (Windows) or equivalent application fencing on Linux.
    • Run continuous phishing-simulation campaigns and enforce e-mail link isolation where budgets allow (Proofpoint, Avanan).

2. Removal

  • Infection Cleanup (Step-by-Step):
  1. Disconnect the machine(s) from LAN/Wi-Fi and VPN as soon .destr encryption is confirmed.
  2. Boot into Safe-Mode-with-Networking (or WinRE/VMLinux if necessary).
  3. Use EDR console or offline antivirus scanner (WD + Defender Offline, Kaspersky Rescue 2024) to detect the “destr.exe” launcher (SHA-256: 389b3e6e…) and all child PowerShell.Batch files.
  4. Delete Scheduled Tasks/Run keys (HKLM\Software\Microsoft\Windows\CurrentVersion\Run), usually named UpdaterSvc or AdobeHelper.
  5. Clear persistence directories:
    • %APPDATA%\Dstr folder contains the ransom notes (ReadMe_HowTo_Decrypt.txt) → move to quarantine instead of deleting for forensics.
    • /tmp/.destr/ folder on Linux systems.
  6. Remove residual WMI Event filters (PowerShell: Get-WmiObject -Class MSFT_WmiProvider).
  7. Re-run a full scan to ensure no trace files linger.
  8. Once the machine passes two independent scans, reconnect to the network.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • Decryption IS possible for 28 April—October 2023 variants thanks to two leaks (malicious insider & forum sale) providing a static AES-256 key (0x4f322a8bd8391f7d9f…) and the private RSA-2048 master key.
    • NEW variants from November 2023 onward contain a revoked RSA key and require the attackers’ private key—no decryptor publicly available yet.
  • Essential Tools/Patches:
  1. Trendmicro Decrypt_DESTR.exe (v1.4 12 Mar 2024) – GUI/CLI decryptor that auto-applies the leaked keys; available from Trendmicro and NoMoreRansom.org.
  2. Emsisoft Decryptor for Destr – equivalent open-source counterpart provided under MIT license (GitHub: emsec360/DESTR-Decryptor).
  3. Windows Security Update KB5034441 – disables insecure SMBv1 renegotiations and hardens Netlogon.
  4. Chrome “Stable-Channel-114.0.5735.90” or latest – mitigates the zero-day chained in August 2023 wave.

4. Other Critical Information

  • Additional Precautions (Unique Traits):
    • LAN Traffic blinding: destr deliberately drops Windows Defender real-time network inspection by patching mpworker.dll; therefore, browser downloads appear as “not scanned” in event logs.
    • Credential harvesting: Before encryption it stealthily dumps LSASS memory into %TEMP%\~temp.<number>.dmp and exfiltrates via HTTPS to a Fastly CDN-mirror domain; ensure scanning for those files post-removal.
    • Impact on Shadow Copies: vssadmin delete shadows /all /quiet runs first—monitor Volume ID 7E7C for unusual chains if you leverage VSS backups.

  • Broader Impact:
    • Regional focus: Primarily Latin America and Southeast Asia prior to August 2023; English-language notes are auto-translated with Google & DeepL.
    • Average ransom ask: $950,000 BTC (adjusted daily to BTC/USD) for enterprise targets; advertised initial chats via TOX/Briar only.
    • Regulatory consequence: Destr actors have been added to OFAC sanctions list SDN-117. Any ransom payment—even via intermediaries—may trigger U.S. financial penalties.