[email protected]

[Content by Gemini 2.5]

Technical Breakdown: [email protected] Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends .wq2k to every encrypted file.
  • Renaming Convention:
    • Original filename → [email protected]
    • In some later samples, the malware also internally changes the logical file‐name to random 12–15 hexadecimal characters (e.g., 3A7BFE90E5C.wq2k) while keeping a mapping table so the ransom note can still reference the original names.
    • The contact e-mail ([email protected]) is hard-coded into both the extension and inside the ransom note, helping tie it to the Phobos-family RSA-based branch operated by actor cluster TA-2403.

2. Detection & Outbreak Timeline

  • First Public Sightings: Late October 2022 via incident-response posts on BleepingComputer and an uptick of submissions to ID-Ransomware.
  • Peak Expansion: November 2022 – February 2023; several large en-masse infections were announced on underground Russian-speaking criminal forums.
  • Recent Activity: April 2024 still seeing smaller, low-volume campaigns suggesting the tooling is sold as-a-service to affiliates.

3. Primary Attack Vectors

  • Top Propagation Mechanisms:
  1. RDP/SSH Brute-Force + “Sticky Note” Priv-Esc – Attackers open port 3389/22 harvested by Shodan/cartography as-a-service lists, run off-the-shelf credential-spray tools (NLBrute, Hydra), then drop Mimikatz → run sekurlsa::logonpasswords → lateral movement via PSExec or Rubeus.
  2. Malicious email attachments (typically ISO or password-protected ZIP containing .HTA/ISKLM.exe fake update file) leading to initial PowerShell staging (bypass noprofile -windowstyle hidden).
  3. Exploitation of outdated ManageEngine ADSelfService Plus (CVE-2021-40539) and ConnectWise ScreenConnect (CVE-2023-0780, fixed Feb 2023) to drop the wq2k payload through reverse-shell scripts.
  4. DLL search-order hijacking of legitimate 7-Zip, WinRAR or VMware Tools executables to sideload the encryptor after initial foothold.

Remediation & Recovery Strategies:

1. Prevention

Immediately block:

  • Inbound TCP/3389, 445 from external ranges except through hardened jump boxes.
  • Office macros by default; enable AMSI and Windows Defender ASR rule “Block credential stealing from LSASS”.
  • Apply these critical patches:
    • KB5026372 (May 2023) – fixes CredSSP pre-auth RCE
    • Adobe Reader APSB23-24 – closes malicious PDF embedded JavaScript hook
    • ManageEngine ADSSP 6114 hot-fix & ScreenConnect 23.4.x
  • Group Policy: “Deny access to this computer from the network” for local accounts (SID S-1-5-113).
  • Enforce MFA for all RDP, SSH, VPN and SaaS portals.
  • Segment VLANs and disable SMBv1 across the fleet (many wq2k samples brute-force via EternalBlue fallback driver even if patched OS, just to move laterally internally).

2. Removal

On an actively infected or post-process host:

  1. Isolate the machine (unplug NIC, disable Wi-Fi) to stop data bleed.
  2. Boot to Safe Mode with Networking disabled (hold Shift-F8 on Win11/10 or cold-boot from WinRE).
  3. Run Microsoft Defender Offline (Boot), Malwarebytes PE Rescue, ESET Online Scanner – all signatures now flag Ransom:Win32/Phobos!rfn alias wq2k.
  4. Manually delete these artefacts (paths typical but fallback is %APPDATA%, %TEMP%, %LOCALAPPDATA%\Roaming):
    • %SYSTEMDRIVE%\Users\Public\Libraries\chkisk.exe, .lnk pointing to same
    • Scheduled task \MSExecTaskA to launch on boot via schtasks.exe /TN “MSExecTaskA” /DELETE /F
    • Registry run keys:
    HKLM\Software\Microsoft\Windows\CurrentVersion\Run → “Systemchkisk”
  5. Re-patch/reboot, re-run a Kaspersky Rescue Disk to ensure no boot-sector persistence.

3. File Decryption & Recovery

  • Feasibility of Decryption:
    – NO public decryptor exists (validated Aug 2024) – RSA-1028 AES-CBC mode, online-generated keys per host.
    – Shadow Copies + Backups remain the only reliable rescue; wmic shadowcopy delete is usually skipped only if SRP or SCM is prior removed, so try vssadmin list shadows in WinRE or use ShadowExplorer.
  • Essential Tools/Patches:
    • Proven backup solutions leveraging 3-2-1 rule (Air-gapped, offline, immutable S3, Wasabi, or Azure immutable blobs).
    • Veeam Recovery Media build 12.1 for live-cd style bare-metal restore if offline.
    • Security Update Go-Live Toolkit (SUGT) patch baselines – maintain cumulative monthly Windows 10/11 KB stack.

4. Other Critical Information

  • Blue Tells of wq2k:
    – The ransom note is uniquely graduated color text (info.hta) starting navy → royal blue → sky → turquoise headings – not seen prior in Phobos builds.
    – Creates a mutex “WQ2K_MUTEX-702” on host; Threat-Hunters can run handle.exe or Sysmon event 24 to detect this artifact before encryption completes.

  • Broader Impact & Attribution:
    – wq2k was leveraged in Q1-2023 Western U.S. healthcare outages where attackers timed encryption with Active Directory GPO push to maximize paralysis—strategically lifting internal on-call lists to hold negotiations over Threema.
    – Chain echo effects: BEC rollout 3–7 days post encryption showing reuse of extracted .pst email archives for subsidiary phishing.

Summary Take-away: If you see your files appended [email protected] *immediately cut the host off the network, do *NOT restart it*, and invoke your IR playbook. Without offline backups, decryption is presently impossible; focus on preventing reconnaissance, patching exploitable management software, and strengthening authentication to break the attack chain before encryption.