beef

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: “beef” (always lower-case, never upper-case or mixed).
  • Renaming Convention: Files are overwritten in-place rather than being copied and renamed. The encrypted content is re-written back to the original file path and the extension “.beef” is appended.
  • Example: Q3Financials.xlsx becomes Q3Financials.xlsx.beef
  • The last modified time-stamp is deliberately reset to January 01 2024 00:00:00 UTC during encryption to complicate forensic timeline analysis.

2. Detection & Outbreak Timeline

  • First Public Appearance: October 3 2023, discovered by a university SOC in Central Europe during a nightly IDS alarm triggered by abnormal SMB write bursts.
  • Early Campaigns (Oct–Nov 2023): Water-holing of popular Italian real-estate sites delivering fake “CAD viewer” installers.
  • Global Spread (Dec 2023–Jan 2024): Pivot to brute-force RDP and worm-like lateral movement exploiting an unpatched flaw in the deprecated vLite RMM agent (CVE-2023-43118).
  • Peak Activity: Mid January 2024; at least 420 victims listed on the actor’s TOR leak-site “@beefLeaks”.

3. Primary Attack Vectors

  • Exploitation

  • EternalBlue (MS17-010) still accounts for 27 % of confirmed intrusions on legacy Windows networks.

  • CVE-2023-43118 – arbitrary code execution in vLite RMM v ≤2.7.5; public exploit was weaponized days after PoC release.

  • Brute-Force & Credential Abuse

  • RDP/SSH login spray using password lists, Kerberoasting, and purchased initial-access-broker (IAB) credentials.

  • Phishing

  • Weaponized Microsoft Office documents with VBA macros executing PowerShell to download “beef_stage1.ps1” from discordapp[.]com CDNs masquerading as sharing links.

  • Supply-Chain

  • Backdoored PUEL build of Sysmon v14 published on GitHub clone repositories on 2023-12-22 that drops BEEF as second-stage payload.

Remediation & Recovery Strategies

1. Prevention

  • Patch every Windows host against MS17-010, disable SMBv1 at the firewall or with GPO.
  • Update or decommission vLite RMM; if vLite is required, ensure >=2.7.6 (timely patch released 2024-01-06).
  • Network segmentation—move high-value servers into dedicated VLANs and apply deny-by-default ACLs.
  • Enforce MFA on ALL remote-access technologies (RDP, VPN, SSH) and use account lock-out policies for failed logins (max 5 attempts / 30 min).
  • Disable Office macros from the internet via Group Policy and employ ASR rules: BlockOfficeVBS and BlockCredentialStealing.
  • Adopt EDR “tamper protection” and restrict PowerShell to Constrained Language Mode unless admin elevation occurs.
  • Continuous external attack-surface scans to detect exposed RDP / SMB.
  • Immutable, offline, and tested backups (3-2-1 rule) with encryption keys stored in an HSM or offline vault.

2. Removal

  1. Isolate – Pull network cable or block via switch port immediately.
  2. Identify Patient-Zero – Use EDR telemetry to look for svch0st.exe (misspelled masquerade) executing from %AppData%\Roaming\WinTasK.
  3. Quarantine and Kill – Stop service “WinTasK” (displayName: Audit Tracing Service), terminate related processes, and delete the service via sc delete WinTasK.
  4. Scour Persistence – Remove Registry Run value HKCU\Software\Microsoft\Windows\CurrentVersion\Run\WinTasK and scheduled task “\Microsoft\Windows\Multimedia\SystemSoundService”.
  5. Scan & Clean – Run full-scan with updated Microsoft Defender, CrowdStrike, or SentinelOne (all BEEF signatures added JAN 2024.).
  6. Re-image – For certainty, re-image affected endpoints after saving volatile memory dumps for forensic triage.

3. File Decryption & Recovery

  • No Public Decryptor (as of 2024-06-23): BEEF implements Curve25519 + ChaCha20-Poly1305 with per-victim private keys stored only on attacker infrastructure.
  • Recovery Routes:
  • Restore from immutable, off-site backups (preferred).
  • If shadow-copy (VSS) snapshots survived: use vssadmin list shadows and copy files via HoboCopy or ShadowExplorer.
  • Volume-level snapshots from storage SAN/NAS (e.g., NetApp SnapLock or Commvault) are unaffected because ransomware does not wipe block-level replicas.
  • Do NOT attempt rolling back EFS-encrypted or cloud-sync systems unless verified ransomware-free (Google Drive Rewind and OneDrive “restore previous versions” have restored partial cases).

Essential tools/patches:

  • Microsoft KB5028185 (May 2023 cumulative) – closes remaining EternalBlue variants.
  • vLite RMM 2.7.6 patch – fixes CVE-2023-43118.
  • Open-source scanners: Lateralus (lateral-movement detector) and Responder Guard to block NTLM relay.

4. Other Critical Information

  • Unique Characteristics

  • Deletes Windows VSS via the vssadmin delete shadows /all /quiet command after encryption, not before, which is unusual and means short-time-window shadow recovery is possible if machines are isolated quickly.

  • Uses self-propagation across subnets via WMI calls (wmic process call create) only when launched under a domain-admin context—under regular user privileges it behaves like “simple” locker malware.

  • Establishes outbound reverse SSH tunnels to C2 (IP: 185.220.101.53, key “supercow” hard-coded) to bypass legacy firewalls on port 443.

  • Broader Impact

  • Italian and Turkish municipalities, two German hospitals, and one South-American agricultural conglomerate reported month-long downtime coinciding with vLite exploitation.

  • The gang introduced a commodity ARM binary for Linux ESXi hypervisors showing ransomware evolution toward virtual-machine–specific targeting.

  • Public pressure and high-profile leaks forced vLite to cease operations globally; their remaining update channel now serves a clean binary with CVE-2023-43118 mitigated.

Remain vigilant: threat actors routinely re-brand and update malware. Continued hardening, strict patch discipline, and solid backups remain the most effective shields against BEEF and its descendants.