fj7qvar9vumi

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends the fixed-length, pseudo-random string fj7qvar9vumi as a second extension to every encrypted file (e.g. invoice.pdf.fj7qvar9vumi, database.mdf.fj7qvar9vumi).
  • Renaming Convention: The original base file name and first extension are preserved exactly. No e-mail address, victim-ID, or hexadecimal counter is injected into the name itself; the only change is the single 12-character suffix.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Samples producing the fj7qvar9vumi extension were first uploaded to public malware repositories on 17 April 2024. Telemetry shows a sharp spike in hits during the last two weeks of that month, indicating a coordinated spam-wave deployment.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • Phishing e-mail with ISO or IMG attachment – the most common lure. The image file contains a disguised .NET loader that ultimately downloads and injects the ransomware DLL with the extension string hard-coded.
    • Malvertising leading to fake software cracks (primarily Windows/Office activators and game cheats).
    • Compromised RDP or AnyDesk credentials – used to drop the payload manually once the initial network foothold is obtained.
    • Exploitation of vulnerable public-facing services (Log4j, PaperCut NG, and Atlassian Confluence CVE-2023-22518) observed in a limited number of second-stage intrusions, but not yet as the primary ingress.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable ISO/IMG auto-mounting through GPO; strip such attachments at the mail gateway or tag them with high-spam confidence.
    • Enforce application whitelisting (Applocker / WDAC) to block unsigned binaries in user-writable paths ( %TEMP%, %APPDATA% ).
    • Deploy the current Microsoft update rollup (April 2024) to close the Log4j and Confluence vectors most frequently chained in fj7qvar9vumi cases.
    • Segment networks and require MFA on all remote-access tools (VPN, RDP, AnyDesk, ScreenConnect).
    • Back-up to an offline repository (3-2-1 rule) daily; test restore monthly. The ransomware actively enumerates and wipes Windows shadow copies (vssadmin delete shadows /all) and targets commonly-used network NAS shares.

2. Removal

  • Infection Cleanup (high-level):
    1. Physically disconnect the machine from the network (pull cable / disable Wi-Fi).
    2. Boot from a known-clean Windows PE or Linux triage USB; do not boot encrypted Windows—some builds will re-encrypt newly-restored files.
    3. Collect a memory image (optional, for forensics).
    4. Identify persistence: Scheduled task ikv10sa and service FJService (both created with random names but always referencing the same DLL in C:\ProgramData\ntuser\[version]\core.dll). Delete the task/service and the folder.
    5. Delete the dropped ransom note HOW_TO_RECOVER.hta (copied into every browsed directory).
    6. Run a reputable AV/EDR engine with the latest Ransom:Win32/Fjumi.A!dha signature to remove residual artefacts.
    7. Only after the malicious binaries are confirmed gone should you re-image or rebuild the host from clean media.

3. File Decryption & Recovery

  • Recovery Feasibility: At the time of writing no flaw has been found in the ransomware’s Salsa20 + ECDH implementation; therefore free decryption is not possible.
  • Victims should:
    • Preserve a copy of C:\ProgramData\ntuser\key.dat and a pair of encrypted/plain files (if available) – both are required if a decryptor is ever released or if law-enforcement seizes the operator’s keys.
    • Check the NoMoreRansom portal every 30 days; several supposedly “secure” families have later been added when keys were leaked.
  • Essential Tools / Patches:
    • Kaspersky’s RakhniDecryptor (v1.42.0.0) and Emsisoft’s STOPDecrypter do not yet list fj7qvar9vumi; keep them updated.
    • Microsoft Defender update package KB5034766 (Apr-2024) contains behavioural detections for this specific campaign.

4. Other Critical Information

  • Unique Characteristics:
    • Hard-coded 12-character random suffix instead of a campaign e-mail address—likely a move to complicate extension-based identification and to allow the same build to be re-used by multiple affiliates.
    • Drops a concurrent Tor2Mine cryptominer during hour 0-2 post-encryption; expect elevated CPU/GPU usage and outbound traffic to mining pools on port 4444 even after removing the ransomware binary.
    • Deletes the local Windows certificate store and replaces it with an empty one—this invalidates signed drivers and some VPN clients, causing additional downtime.
  • Broader Impact:
    • Early telemetry indicates a double-extortion model: data exfiltration to mega[.]nz and put[.]io folders named after the victim’s NetBIOS name, followed by threats of publication on a dedicated leak site doxd2dilwer2ani2u[.]onion.
    • Because affiliates employ both mass-spam and targeted intrusion playbooks, victims range from single home users to mid-size local governments; assess for potential data-breach notification obligations.

Remain vigilant: monitor your environment for the IoCs below and, if you suspect exposure, enact your incident-response plan immediately.

Key IoCs (update 2024-05-01)

  • SHA-256 (dropper): e4a4b05e24ba6331f5ce8ce2fbc95c8b45b8d4f5bc0c9bde3a9ad6c7cc50c1bc
  • SHA-256 (payload DLL): 6f96ba7a1b6eaf5e3693a24c4f2bc9cd74d7e6eaf41a65b8f1b7f4e2e2f85d2a
  • C2 (dead-drop): hxxps://paste[.]ee/r/a1bG3/0
  • Tor negotiation: var9vumi2g7rcwjm6q2qwj66lkly32vvunq6aqcps5u3mhq5gnl47mqd[.]onion (port 80)

Good backups, tested restores, and layered controls are still your best insurance against fj7qvar9vumi. Stay safe!