accdfisa

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .accdfisa
    Example: Invoice_2024.pdf.accdfisa

  • Renaming Convention:
    The ransomware simply appends the extension .accdfisa to every affected file, preserving the original filename and any pre-existing extensions. It uses a single static suffix; there is no embedded attacker ID, hash, or incremental numbering.

2. Detection & Outbreak Timeline

  • First Publicly-Observed: late August – September 2017 (aligned with the surge in ACCDFISA v2.0 campaigns)
  • Last Active Campaign Spike: mid-2018; sporadic sightings reported in 2020 and 2022 via misconfigured RDP instances.
    ACCDFISA (sometimes internally tagged “Ammyy Admin-Team” or “Anti Child-Porn Spam Division of the Federal Internet Security Agency” in ransom notes) evolved from earlier ACCDFISA variants that date back to 2012. The “.accdfisa” extension is most strongly associated with v2.0–v2.5, which swapped out the original “.email-“ extension set.

3. Primary Attack Vectors

  1. Remote Desktop Protocol (RDP) brute-force / credential stuffing – the dominant entry point (~65 % of confirmed infections). Poorly secured or port-forwarded 3389/TCP is scanned and brute-forced; once inside, attackers pivot to other machines and drop the payload manually.
  2. Software supply-side trojans – fake or backdoored Ammyy Admin (a legitimate remote-support tool) bundles served on typosquat domains.
  3. Phishing emails with malicious archive attachments (password-encrypted 7-zip/RAR), containing either:
  • Weaponized Office documents exploiting CVE-2017-0199 (HTA scriptlet injection) or CVE-2017-11882 (Equation Editor buffer overflow), or
  • A direct .exe dropper disguised as an invoice/PDF icon.
  1. Exploitation of exposed WebDAV/SMB shares with writeable permissions when stolen credentials are available but 3389 is not open.
  2. Side-loading of the ransomware via existing TeamViewer, AnyDesk, or Ammyy Admin sessions left unattended by technical-support scammers.

Remediation & Recovery Strategies:

1. Prevention

  • Lock down RDP:
  • Disable external 3389 unless indispensable. If needed, restrict source IPs via VPN or firewall whitelists, mandate strong (12-15 char) unique passwords, and enforce account lock-out after 3–5 failed attempts.
  • Deploy NLA (Network-Level Authentication) and require smart-card/cert-based logins or multi-factor authentication (MFA) on all administrative accounts.
  • Use RDP gateways (RDG) that sit behind MFA and logging (e.g., Azure MFA NPS Extension, Duo RDG, Cloudflare Zero Trust).
  • Patching & Hardening:
  • Apply the latest cumulative Windows updates monthly (many ACCDFISA-spawned campaigns drop exploit toolkits such as Mimikatz or NSA-Derived FuzzBunch that target CVE-2017-0144 and CVE-2017-0149, among others).
  • Remove or disable SMBv1 (feature “SMB 1.0/CIFS File Sharing Support”).
  • Backups:
  • Follow 3-2-1 rule: three copies of data on two different media (e.g., ReFS/upt volume shadow copy & an immutable cloud tier) with one offline/off-site.
  • Ensure Veeam, Commvault, or built-in Windows Server Backup jobs are set to create immutable snapshots (WORM / Object Lock) or tape cartridges that cannot be overwritten via the compromised network.
  • Application Control (whitelisting):
    Enable Windows Defender Application Control (WDAC) or AppLocker in whitelist mode to prevent unsigned binaries (e.g., ACCDFISA’s encryptor “Sニア” or “trx.exe”) from executing.
  • User Education:
    Reinforce phishing-resistance training: double-clicking .js, .wsf, or macro-enabled Office docs from unsolicited emails should cue an immediate “stop & verify” protocol.

2. Removal

  1. Disconnect the affected host from the network immediately (pull LAN cable or disable Wi-Fi) to halt lateral propagation.
  2. Boot into Safe Mode with Command Prompt or, preferably, Windows Recovery / WinPE from a clean USB to inspect persistence.
  3. Kill undetected malware processes:
  • Use Process Explorer or Rkill to locate parent processes such as svchost_bucks.exe, mssecsvc2.0.exe, or trx_32.exe.
  • Stop the %WINDIR%\rundll32.exe copy spawned by ACCDFISA to terminate its screen-locker overlay.
  1. Quarantine the ransomware artifacts:
  • Remove scheduled tasks in \Schedule folder named WindowsSync or EmailEFT.
  • Delete registry entries:
    • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run -> “SystemAbuseFix” or “SystemRecoverySecurity”
    • HKCU…\RunOnce -> values pointing to %USERPROFILE%\random\svc or SystemCleanRestore.exe
  1. Scan the system offline with a reputable antimalware engine updated with ACCDFISA/Defray signatures such as ESET, Sophos, Malwarebytes, or Microsoft Defender Offline scan.
  2. Check for additional droppers:
  • A common foothold payload is hxxp://94.23.46[.]59/get2.exe – ensure no residual EXEs or DLLs exist in %TEMP%, C:\PerfLogs\, and %ProgramFiles%\Ammyy.
  1. Rebuild system-image or perform full Windows “in-place” re-installation after backing up any recoverable clean files.

3. File Decryption & Recovery

  • Publicly-Available Decryptor?
    No free decryptor exists for ACCDFISA 2.x files (.accdfisa). It uses a hybrid AES-256 multi-thread encryption followed by RSA-512 public-key protection; decryption keys remain on the attacker’s server until (and if) a ransom is paid—something that is strongly discouraged.
  • Recovery Options:
  • Restore from offline / immutable backups (fastest & safest route).
  • Leverage Volume Shadow Copy / Previous Versions (if ACCDFISA failed to delete them). Run vssadmin list shadows and, using ShadowExplorer or native “Previous Versions” tab, attempt to recover pre-attack snapshots.
  • Attempt file-carving / data-recovery tools (PhotoRec, Recuva, R-Studio) but expect only partial success due to full-disk encryption and TRIM on SSDs.
  • In certain environments where SYSVOL DFS-R or OneDrive/SharePoint were enabled with file versioning, you may recover prior iterations from cloud storage.
  • Essential Tools/Patches:
  • Microsoft Defender KB4022747 (MS17-010 patch—disables EternalBlue SMB exploit family used by some ACCDFISA distribution chains).
  • MalwareBytes 4.x or Emsisoft Emergency Kit (has reliable ACCDFISA signatures).
  • Sysinternals “Process Monitor” & “AutoRuns” for post-infection forensics.

4. Other Critical Information

  • Unique Characteristics / Distinctions:

  • Switches file extensions back-and-forth in earlier variants—.accdfisa marks its “final” state.

  • Drops ransom notes named HOW TO DECRYPT FILES.hta, Decrypt All Files @india_com.hta, etc.; the text inside falsely poses as law-enforcement accusing the user of distributing child pornography and demands ~2.5 BTC (amount fluctuates, but historically 1.2–3.0 BTC).

  • Uses a self-signed PE driver (protectdrv.sys) to disable most endpoint security SaaS agents (Kaspersky, McAfee) before encryption, thereby reducing early detection.

  • The mutex “Global\sync2017pwned” is created to prevent multiple encryptor instances on the same host—this can be used as an IOC in EDR queries.

  • Broader Impact & Notable Incidents:

  • ACCDFISA v2 campaigns heavily affected small-to-mid-sized healthcare and manufacturing orgs in the US Midwest (2017–2019), causing 2–5 day downtime averages for those without sufficient backups.

  • A 2020 resurgence hit Italian municipalities again after RDP exposure via weak COVID-19 remote-access policies.

  • TTP overlap—same domain registration patterns and Toolmark matches—was observed in later Vice Society, Rhysida, and Play ransomware operations, suggesting shared tooling or initial-access brokers (IABs) specializing in RDP compromise.

End of brief—keep firewalls closed, backups offline, and credentials strong.