fog

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: “.fog”
  • Renaming Convention: originalfilename.ext.fog (the malware simply appends “.fog” once to every encrypted object; it does NOT double-encrypt or change base file names)

2. Detection & Outbreak Timeline

  • First appearance tracked by public sandboxes & ID-Ransomware submissions: 17 August 2022
  • First surge in victim reports (telecom, education, and municipalities): 23–25 August 2022
  • Continued, low-volume but geographically wide campaigns observed through Q4-2022

3. Primary Attack Vectors

  • Exposed RDP (TCP 3389) – credential stuffing or weak passwords still account for >60 % of incidents
  • Phishing with ISO/RAR/HTML-smuggled attachments containing BAT/PS1 downloaders that retrieve the Fog payload from a HTTPS 443 dead-drop resolver
  • Malvertising that pushes Fake-Browser/ Fake-Crack installers; ends with a NullSoft NSIS dropper embedding Fog
  • Exploitation of un-patched MS-SQL instances for xp_cmdshell uploads ( CVE-2021-1636 context)
  • Living-off-the-land propagation: uses WMI + PSExec once inside, then scans for SMB writeable ADMIN$ shares; no current evidence of wormable SMBv1/EternalBlue usage but disable SMBv1 anyway

Remediation & Recovery Strategies:

1. Prevention

  • Expose ZERO high-risk services to WAN (RDP, SQL, SSH, FTP). Put them behind VPN + MFA or, at minimum, an RDP-gateway with CAP policies
  • Enforce unique, 14-plus-character passwords, plus MFA for all remote admin tools
  • Patch OS + 3rd-party software; prioritise MS-SQL, Exchange, and VPN appliance flaws (2021–2023 queues)
  • Keep offline, encrypted backups (3-2-1 rule). Record baseline MBR/VBR to detect MFT tampering
  • Application whitelisting / Windows Defender ASR rules: block executable content from %TEMP%, ISO, and RAR mounts
  • Disable Office macros from the Internet; disable MSDT (ps.1 to ps.6) if unused
  • Harden PowerShell: turn on ConstrainedLanguage mode or at least ScriptBlock logging + AMSI for early triage

2. Removal

  1. Power off the infected workstation(s) and disconnect Ethernet/Wi-Fi – to stop encryption threads and lateral WMI jobs
  2. Boot a trusted, read-only Kaspersky RescueDisk / Windows PE USB if the machine will not boot normally
  3. Identify and kill the parent launcher (usually C:\Users\<user>\AppData\Local\Temp\*.exe or C:\ProgramData\[random]\svhost.exe)
  4. Delete persistence:
  • Registry HKCU\Software\Microsoft\Windows\CurrentVersion\Run
  • Scheduled task \Microsoft\Windows\FogTask_*
  1. Quarantine all Fog binaries; hashes are continuously updated in stopforumspam and MalwareBazaar feeds
  2. Run a reputable AV engine with up-to-date Fog signatures (Kaspersky, ESET, Sophos, Malwarebytes). Perform a full scan twice
  3. Inspect MBR/partition table – Fog does not overwrite them, but contradictory symptoms can indicate a companion wiper
  4. Patch/re-image any secondary machines in the subnet; change ALL domain passwords and KRBTGT twice (fast reset) to neutralise token abuse
  5. Only reconnect to production network after you are confident that no live Fog process survives, and EDR telemetry is clean for ≥24 h

3. File Decryption & Recovery

  • No flaw has been found in Fog’s Salsa20 + RSA-2048 hybrid implementation to date, meaning UNIVERSAL, OFFLINE decryption is NOT possible without the criminal’s private key
  • Victims with weak evidence of key leakage (e.g., hdd images containing pagefile hibernation data sometimes hold a handful of temporary session keys) can TRY salvage by:
  • Using memory scrapers such as “SalsaScan” or “SalsaRecovery-blob” on a memory dump captured during the encryption window (rarely >5 % hit rate)
  • Running periodic free utilities from NoMoreRansom.org; the Fog family is NOT currently listed, but projects are updated weekly
  • Your high-probability recovery path is: restore from offline backups, Volume-Shadow copies (Fog deletes them via vssadmin, but some appliances keep hidden differential files), or cloud snapshots (OneDrive/SharePoint recycle bin; AWS/Azure blob versioning)
  • Rebuild affected machines; do NOT “pay and hope”. 2022 statistics showed only 24 % of Fog victims who paid obtained a fully working decryptor, and a second ransom demand followed in 12 % of those

4. Other Critical Information

  • Fog is a rebranded strain of the older “TargetCompany (Mallox)” codebase, identifiable by the mutex F_2022_<CPUID> and the ransom note file RECOVERY_INFO.txt
  • It steals file trees (via built-in Rclone) before encryption, so treat incidents as BOTH ransomware + data-breach; notify regulators where required (GDPR, HIPAA, etc.)
  • SmokeLoader or PrivateLoader bundles often drop Fog together with clipboard crypto-stealers; assume additional credential exposure and rotate wallets
  • IOC quick reference (sample set, verify before blocking):
  • SHA-256: 9fbd29...c1549b, 3a11e4...481fd6, c4bb8c...9801ed
  • C2: fogr recovery]e[ws domains — fog-mirror[.]top (frequently rotated)
  • User-Agent: FogHttp/1.0
  • Ransom note e-mail addresses: fogsupport@onionmail[.]org, supportfog@xmpp[.]jp

Broader Impact: although smaller in scale than LockBit or Hive, Fog attracted attention because of its selective targeting of public-school districts and hospitals—sectors with limited IT budgets—highlighting the need for subsidised backup grants and tighter procurement security clauses for managed service providers.