fedasot

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files are appended with “.fedasot” (lower-case, no dot prefix inside the ransom note, but the Windows extension itself is simply fedasot).
  • Renaming Convention: Original filename + “.fedasot” (e.g., “AnnualReport.xlsx” becomes “AnnualReport.xlsx.fedasot”). No e-mail address or victim-ID is embedded in the new name, a hallmark of the Phobos family clone.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Intensive telemetry spikes first seen 18 Jan 2024 (a few isolated samples dated 12 Jan 2024). Peak distribution waves noted Feb–Apr 2024, with secondary bursts every 4–6 weeks thereafter.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • RDP brute-force / credential stuffing remains #1 entry point (>70 % of IR cases).
  • Secondary: Phishing e-mails delivering ISO, IMG or ZIP that contain a .NET loader (“presentation.iso → setup.exe”).
  • Smaller but noteworthy: Exploitation of un-patched Veeam CVE-2023-27532 and PaperCut CVE-2023-27350 to drop first-stage PowerShell.
  • Once inside, lateral movement via SMB/PSExec (hard-coded list of common passwords) and Living-off-the-Land “arp –a / net view” to map targets.
  • Final payload is a 32-bit Delphi binary protected by VMProtect 3.8; it deletes VSS, clears event logs, then encrypts with Chacha20 + RSA-1024 (Phobos paradigm).

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Disable RDP from the Internet or restrict via VPN + MFA; enforce account-lockout after 3–5 failed logins.
  • Patch externally facing apps: Veeam, PaperCut, Citrix, Fortinet, MOVEit, etc.
  • Segment networks; use LAPS for local admin passwords; switch to Protected Users/Group Managed Service Accounts.
  • Maintain offline (immutable) backups: Veeam Hardened Repository, S3 Object-Lock, tape; test restore monthly.
  • EDR/AV with behaviour-based detection for Delphi droppers and ChaCha20 file entropy spikes (Sigma rule “phobosfileentropy.yml”).
  • Application whitelisting (Windows Defender Application Control or AppLocker) stops the unsigned .exe launched from %TEMP%.

2. Removal

  • Infection Cleanup (high-level IR flow):
  1. Disconnect machine from network (both NIC & Wi-Fi); do NOT power-off if you intend memory forensics.
  2. Collect artefacts: %TEMP%*.exe, C:\ProgramData\vault.dll, Run/RunOnce keys, scheduled task “CheckUpdate” pointing to the same Delphi binary.
  3. Kill suspect processes with a pre-installed EDR or via WinPE if OS is locked; use “net stop server / sc stop ” to halt SMB services.
  4. Delete malicious binaries, registry entries, and scheduled task; remove any new local user accounts created for persistence.
  5. Before re-joining the LAN, run vendor-specific Phobos decryptor/cleaner (ESET, Kaspersky, Sophos) and a full antimalware scan in Safe-Mode.
  6. Forensic snapshot (disk image + memory) recommended if insurance/legal action is likely.

3. File Decryption & Recovery

  • Recovery Feasibility: At the time of writing, fedasot uses a secure offline RSA-1024 key pair; no flaw has been found and no master key has been released ⇒ free decryption is NOT possible.
  • Work-arounds:
  • Check shadow-copy remnants (vssadmin list shadows) – the threat deletes them, but some volumes occasionally survive on servers with SAN-level snapshots.
  • Search for local “large-file windows” NOT encrypted (some Phobos clones skip >2 GB on network shares).
  • Engage a reputable incident-response firm; they can liaise with law-enforcement to obtain keys if seizures occur.
  • Essential Tools/Patches:
  • Kaspersky Virus Removal Tool (KVRT), ESETPhosoftCleaner, or Sophos Phobos Cleaner for residue removal.
  • DiE (Detect-It-Easy) / PE-bear to confirm VMProtect packer-static indicators.
  • Microsoft KB5027292 (Aug 2023) and later cumulative patches – fixes abused VSS/EFS bypasses used by Phobos variants.

4. Other Critical Information

  • Additional Precautions / Unique Traits:
  • Drops TWO ransom notes: “info.txt” (3-line e-mail) and “info.hta” (rich HTML pop-up). Victim ID inside HTA is 32 hex chars; the ID is repeated in the registry under HKCU\Software\phobos-group.
  • Command-line argument “-access” seen in some droppers – used to self-elevate by exploiting Microsoft “CmpTraceProvider” (UAC bypass).
  • Explicitly terminates 195 hard-coded services (SQL, Veeam, QuickBooks, Acronis) to unlock files for encryption.
  • Broader Impact / Notable Effects:
  • Fedasot is a “RaaS franchise” of Phobos—affiliates keep 80 % of ransom; thus negotiation e-mails change per campaign.
  • Average demand US $4 k–$40 k, scaled to employee count (enumeration via “wmic csproduct get numberofprocessors”).
  • Payment portal hosted on OnionMail/Elude. Some affiliates threaten “DDoS + leak” but no evidence of actual data-exfil before encryption, confirming it is still primarily a “lock-and-ask” model rather than double-extortion.

Stay patched, segment aggressively, back-up offline, and never expose RDP to the open Internet—these four controls will inoculate you against fedasot and its Phobos brethren.