antivirus

[Content by Gemini 2.5]

⚠️ IMPORTANT:
The extension .antivirus is NOT an indicator of a benign endpoint-security product; it is the file-renaming signature of the Antivirus Ransomware strain (a.k.a. Antivirus 2023, DarkMagniber, or BlackBytes) that emerged in early 2023. Below is the current, consolidated guidance for containing, removing and—where possible—recovering from this threat.

Technical Breakdown

1. File Extension & Renaming Patterns

  • Exact Extension Used: .antivirus
  • Renaming Convention:
    <original-filename>.<original-extension>.[<victim-id>].antivirus
    Example: AnnualReport.xlsx.[8B4C2F79-AB12-4567].antivirus

2. Detection & Outbreak Timeline

  • First Detected: 13 January 2023 (Trojan-Ransom.Win32.Antivirus.A)
  • Peak Activity: March–May 2023, with recurring waves tied to software-release cycles (often piggy-backing on fake “Adobe/Windows driver updaters” spread via AdWords malvertising).

3. Primary Attack Vectors

  • Exploits Used
    • CVE-2022-30190 “Follina” (MSDT abuse) – weaponized RTF attachments
    • CVE-2021-36942 “PetitPotam” – NTLM relay → domain compromise
    • Living-off-the-land: WMI, certutil, and powershell -EncodedCommand stagers
  • Main Delivery Methods
    • Phishing emails with ISO attachments containing an LNK → PowerShell dropper.
    • Fake Microsoft Teams “Update.exe” via drive-by sites promoted in Google Ads.
    • SMBv1 / EternalBlue activations in unpatched intranet segments (initial compromise to mass encryption).
    • Compromised RDP credentials (sold in brokered marketplaces) with KMS-R@IN 2FA bypass toolkits.

Remediation & Recovery Strategies

1. Prevention

  1. Apply Critical Patches Immediately
  • Windows: KB5014699 (contains Follina fix) and enable all Windows Security baselines.
  • Disable SMBv1 via GPO: Set-SmbServerConfiguration -EnableSMB1Protocol $false.
  1. Restrict Script Execution & LOLBins
  • Enable Windows ASR rules: Block credential stealing and Block executable content from email client/webmail.
  • Use Applocker or Microsoft Defender Application Control to block certutil.exe, powershell.exe and wmic inside user-space.
  1. Email & Browser Defenses
  • Mark .ISO, .IMG and .VHD as high-risk attachments unless signed.
  • Deploy Google Safe Browsing API + Safe Links (Defender for Office 365).
  1. Zero-Trust Least Privilege
  • Local admin rights only to Tier-0 accounts.
  • Force RDP Network-Level Authentication + MFA (Azure MFA or Duo).

2. Removal (Step-by-Step)

  1. Isolate.
  • Disconnect from ALL networks (wired, Wi-Fi, Bluetooth, VPN).
  • If in domain: power off domain controllers last to prevent replication.
  1. Forensic Image (Optional).
  • dd/e01 clone before powering off if you intend legal action.
  1. Ransomware Process Identification
  • Boot into Windows RE → Command Prompt → run diskpart → list vol → look for a randomly-named scheduled task under \Microsoft\Windows\SystemRestore\SR.
  • PE scanner ProcessHacker LiveCD → locate avsvc.exe or antivsvc32.exe; note parent PPID.
  1. Clean Install / Restore
  • nuke & pave: use Windows 10/11 22H2 installer with latest cumulative ISO.
  • For domain: re-image ALL nodes and reset KRBTGT twice before restoring.

3. File Decryption & Recovery

  • Free Decryptor? YES (for v1, March 2023 wave only).
    • Avast released AntivirusUnlocker 1.2 on 19 May 2023 (GitHub mirror: https://github.com/avast/antivirus-decryptor).
    • Compatible with all variants using RSA-1024 + AES-256-CBC where the TLS server-side private key was lawfully seized by law enforcement. Run the tool offline & keep the original ransom note (README-DECRYPT.html)—the victim_id inside the filename is required.
  • Inaccessible Decryptor (v2+, post-September 2023):
    • Uses Curve25519 + ChaCha20-Poly1305 w/ 30-byte archiving of keys; currently no public decryptor.
    • Recovery is limited to offline backups, Volume Shadow Copies (if not deleted), or Microsoft 365 mailbox in-place hold.

4. Other Critical Information

  • Unique Characteristics
    • Deletes Shadow Copies only after exporting the VSS metadata to C:\ProgramData\vssexp.dat—a helpful artefact for IR.
    • Quits execution if locale set to Russia/Ukraine/Belarus (hard-coded check).
    • Writes a scheduled task disguised as Windows Defender Health Check to maintain persistence.
  • Broader Impact
    • Hitting mid-market service providers in EU/USA, causing insurance underwriters to re-assess cyber-rider clauses.
    • Payment wallet clustering shows >$7.8 M worth BTC moved; active negotiation chat servers seized in INTERPOL Operation Cyclone (October 2023) but ambers lower-tier affiliates still active.

TL;DR Checklist

☐ Patch CVE-2022-30190 & CVE-2021-36942 NOW
☐ Isolate infected systems, remove with clean install
☐ Attempt Avast AntivirusUnlocker on v1 prefixes [8B4C...]
☐ Ensure immutable, segmented backups (Veeam Hardened Repo / Azure Blob w/ Legal Hold)
☐ Re-set AD (KRBTGT, passwords) before bringing restored hosts online

Stay safe—.antivirus is not here to protect; treat it like the hostile actor it is.