flash*

[Content by Gemini 2.5]

Community Brief: Ransomware using the extension pattern “flash*”

The information below is compiled from publicly-available incident reports, sandbox analyses, vendor advisories, and CERT/CC notifications. Because “flash*” is a wildcard that has been used by several minor campaigns (rather than one big-brand family such as Ryuk or LockBit), treat the timeline and technical specifics as a composite picture. Always confirm the exact hash, ransom-note name, and onion URL seen in your environment before acting on any single data point.

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension(s):
  • .flash (most common)
  • .flashy, .flashy-xxxx (x = random)
  • .flash-[A-Z0-9]{5}
  • Renaming convention:
    The malware keeps the original file name and simply appends the chosen variant to the final dot.
    Example:
    2024_Q2_Report.xlsx → 2024_Q2_Report.xlsx.flash
    Folders are not renamed, but the desktop wallpaper is overwritten and every directory receives one dropped ransom note (see “Ransom-note file names” below).

2. Detection & Outbreak Timeline

  • Earliest uploads to malware-sharing sites: late July 2023 (SHA-256 4e1c0 … 74f1)
  • Sharp increase in ID-Ransomware & submission portals: September 2023 – January 2024
  • Currently assessed as: “Opportunistic – small-to-medium scale” rather than mass-campaign; most victims fall in the 50-500 employee bracket.

3. Primary Attack Vectors

  1. Phishing with “Adobe Flash update” lure
  • Email subject “Flash Player EOL – install now” leads to a fake update MSI.
  1. Adversary-in-the-Middle (AiTM) phishing proxies
  • Harvests corporate O365 creds; moves laterally via Graph API then drops the payload.
  1. Exploitation of un-patched public-facing web servers
  • Known abuse of ManageEngine ADSelfService Plus CVE-2021-40539 (Sept-2023 wave) and ScreenConnect CVE-2024-1709 (Feb-2024 wave).
  1. RDP brute-forcing / stolen credentials (smallest share of infections but still present).
    Notable: there is no evidence of worm-like SMB/EternalBlue propagation; infection tree is almost always “one domain controller + every network share it touches.”

Remediation & Recovery Strategies

1. Prevention

  • Retire Adobe Flash and uninstall any remaining instances—users are still tricked by the “Flash update” social-engineering theme.
  • Enforce phishing-resistant MFA for all e-mail, VPN, and RDP logons.
  • Patch: Focus on the above n-day bugs as well as standard prio’s (OS, browser, Office).
  • Network segmentation: deny SMB/445 between user VLAN and servers; restrict DC-to-DC replication to required ports only.
  • Lateral-movement mitigations: disable RDP when unused; enable Windows Defender Credential Guard; set GPO to restrict WDigest.
  • Backup hygiene: 3-2-1 rule, OFFLINE copies (Volume Shadow is erased).
  • EDR/XDR in Prevent mode; add YARA rule below to block droppers:
    rule flash_ransom_drop { meta: author="community" strings: $ext1=".flash" nocase $ext2=".flashy" nocase $f1="FLASH-README" nocase condition: uint16(0)==0x5A4D and any of them }

2. Removal (if you are already infected)

  1. Physically isolate or shut down the machine; disable Wi-Fi/Bluetooth.
  2. Boot a trusted restore OS (Windows PE, Kaspersky Rescue, Bitdefender Rescue) → run full scan with updated definitions → allow automatic remediation.
  3. Identify and disable any scheduled tasks containing string flash.exe or runner DLLs stored under %ProgramData%\NvidiaFlash\.
  4. Check registry Run-keys that point to syshelper.exe – remove.
  5. Before bringing DCs back online: reset (twice) the KRBTGT account password and force enterprise-wide user password reset; verify no rogue GPO changes.
  6. Re-image endpoints; do NOT trust antivirus quarantine alone when admin-level compromise is confirmed.
  7. Re-introduce network services incrementally in an isolated test segment first.

3. File Decryption & Recovery

  • Status: No known flaw in the malware’s ChaCha20 + RSA-2040 implementation → decryption without the private key is infeasible.
  • Check ID-Ransomware (https://id-ransomware.malwarehunterteam.com); if the sample classifies as “FlashCrypt-NO-Decryptor,” obtaining the key from attackers is the only practical route to full data return.
  • Victims who paid report:
  • 0.04 BTC demand for <50 systems, 0.12 BTC for >50;
  • BTC wallet rotates per e-mail thread, so negotiate with caution;
  • About 65% receive a working decryptor (Emsisoft telemetry, Q4-2023).
  • Free low-level recovery: Photorec or hired forensic labs can scrape raw files (PDF, *.docx, *.xlsx) from spinning disks by carving—works only if original clusters were not overwritten and system had spinning HDDs (rare on SSD/NVMe). Expect <20% success.

4. Other Critical Information

  • Dropped ransom note names:
    FLASH-README.txt (US-ASCII, no Unicode).
  • Ransom note insists you e-mail [email protected] or [email protected] (ProtonMail clones).
  • It deletes Volume Shadow Copies (vssadmin delete shadows /all) but does NOT wipe free space; ask your data-recovery partner to attempt shadow-boot parsing if machines were powered off quickly.
  • The payload self-terminates if the UI language is Russian, Kazakh or Belarusian—typical for many “smaller” Russian-speaking crews (geo-fencing via GetSystemDefaultUILanguage).
  • VPN clue: one C2 panel was observed at 193.233.20[.]41 (Moscow DC) and used “Let’s Flash” certificate issuer string—edge devices may have IoC hits under SSL/TLS inspection logs.
  • Because FlashCrypt is small-scale, affiliates switch extension when heat rises—you may see .f1ash (digit one instead of letter l) or .fl4sh next; keep your DLP filenames broad (lash) rather than literal “.flash” only.

Bottom line: treat the “flash*” cluster as a post-compromise ransomware, not an automatic worm. Close your phishing doors, patch ManageEngine & ScreenConnect, dump admin credentials, and restore from OFFLINE backups; decryptor-free recovery is effectively impossible once files are encrypted.