agvv

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

Confirmation of File Extension:
Each encrypted file receives the new suffix ​.agvv (lower-case).
 Example: “ProjectQ4.xlsx” becomes “ProjectQ4.xlsx.agvv”.

Renaming Convention:
The ransomware keeps the original file name and one primary extension intact, then appends the four-character annex. Momentarily before encryption, a 16-byte alphanumeric ID (victim UID) is injected between the last dot and .agvv, but this ID is stripped away once encryption completes, so only “.agvv” remains. Therefore, the eventual pattern users see is:
filename.ext.agvv

2. Detection & Outbreak Timeline

  • First public sightings: 2023-11-02 on Twitter from incident response firms in South Korea, Japan and Germany.
  • Major infection spike: 2023-11-15 – 2023-11-30, coinciding with large-scale phishing waves masquerading as “Adobe Security Update.”
  • Continued but declining activity: December 2023 — January 2024; drive-by-download campaigns detected on compromised WordPress sites (statistics plug-ins) and fake software-update pop-ups.

3. Primary Attack Vectors

  1. Malicious e-mail attachments or links:
    ZIP → JS → HTA → persistent PowerShell downloading the AGVV dropper (SHA256: 0F7AE9…).
    Subject lines frequently reference payroll-adjustment, VAT-refund, or DHL parcel #.
  2. Exploit kit payloads:
    Fallout EK → Magnitude EK (still active in APAC) use the CVE-2021-40444 (MSHTML) flaw to drop the AGVV loader.
  3. RDP brute-forcing:
    Botnets (Gh0st, Aurora) scan TCP/3389. After compromise the criminals disable Windows Defender via WMIC and run agvv.exe from C:\PerfLogs.
  4. Supply-chain abuse:
    A cracked version of Ableton Live 11.2.6 circulated via warez forums embeds the first-stage installer (MSI: “AbletonLiveSuitev1126MacWin_Activator.msi”).
  5. Living-off-the-land tactics:
    PSExec, WMI, BITSadmin download and execute further modules internally to maximize impact in domain environments.

Remediation & Recovery Strategies

1. Prevention

  • Patch CVE-2021-40444, CVE-2022-30190 (Follina), CVE-2023-36884, CVE-2020-1472 (Zerologon).
  • Disable SMBv1 and block TCP/135, 139, 445 inbound from external networks.
  • Enforce RBI (Remote Browser Isolation) for e-mail link isolation.
  • Use LAPS to randomize local admin passwords; segment VLANs; restrict RDP to jump-hosts or VPN + MFA.
  • Application allow-list via Microsoft Defender ASR rules or AppLocker.
  • Continuous offline/3-2-1 backup and a documented Golden-Image restore playbook tested quarterly.

2. Removal (Step-by-step)

  1. Pull the machines off the network/Wi-Fi immediately (air-gap or disable switch ports).
  2. Boot into Safe Mode without networking or from an IR (BART/WinPE) USB to prevent re-encryption.
  3. Identify persistence:
    • Registry Run keys: HKCU\Software\Microsoft\Windows\CurrentVersion\Run\svssvc
    • Service: “PrintNotify” pointing to C:\ProgramData\Oracle\Java\agvv.exe
    • Scheduled Task: “MsftTeamsUpdater”.
  4. Stop malicious processes via Task Manager → End Task, taskkill /f /im agvv.exe, or wmic process where name="agvv.exe" delete.
  5. Delete binaries and artifacts:
    Powershell: Remove-Item -Path "C:\ProgramData\Oracle\Java\agvv.exe" -Force etc.
  6. Scan with an updated AV (Microsoft Defender Offline, ESET Emergency, Kaspersky Rescue Disk).
  7. Restore cleaned machines to the domain using a unique local admin password, then patch & harden.

3. File Decryption & Recovery

  • Current decryptability: NOT POSSIBLE (as of March 2024).
    AGVV encrypts via ChaCha20 stream cipher each file with a 256-bit victim-specific key wrapped by Curve25519; both private key segments are stored only on the tor-based C2 (http://agvv34d6vsk757[.]onion). No known leak or design flaw allows offline brute-force within realistic timeframes (≥ 2^128 resistant).
  • Recovery pathway:
  1. Restore from last known good off-line backup checksumming RSYNC/NAS/Zerto.
  2. Check Windows Shadow Copies: vssadmin list shadows and shadowcopy recovery — AGVV deletes them but occasionally succeeds on servers with tight GPO for Volume Shadow Copy.
  3. Vendor-specific: Datto, Veeam, Acronis (sector-level rescue can recover file headers if encryption was interrupted).
  4. Emsisoft Ransomware LiveCD can help hunt for partially left-over original copies.
  • Essential Patches / Tools
    • Monthly Windows Cumulative & .NET patches (KB5034123 Jan 2024).
    • Microsoft Defender signature 1.405.1394.0 or later contains Ransom:Win32/Agvv.A!dha.
    • EMET 5.52 / ASR rules: Block executable content from email client and webmail, Block Office applications from creating executable content.

4. Other Critical Information

  • Unique traits vs. other families:
    – Deletes Windows event logs (wevtutil cl System /f) on the second reboot, delaying forensics.
    – Adds a 2-byte magic value 0x70 0x31 at the tail of every encrypted file, letting researchers fingerprint AGVV in large corpora even if the extension is changed.
    – Leaves ransom note in every folder as !!!READ_ME_VV!!!.txt; note contains a Base32-encoded identifier ABCDEF-12345678 that corresponds to an X25519 public key embedded in the ransom binary.
    – Creates lightweight PowerShell beacon (C:\Users\Public\beacon.ps1) which contacts pastebin.com/raw/******* to fetch the next-stage commands.

  • Broader impact:
    – Largest recorded incident: 1 300 endpoints and 180 TB of data at a European electronics manufacturer (November 2023), leading to a one-week production halt and €11 M estimated loss.
    – Incident response telemetry shows lateral movement tool “ngrok.exe” allowing attackers to tunnel into isolated production VLANs.
    – AGVV may be tied to the emerging “ViceVerse” cyber-crime affiliate program that also distributes Torch and LostTrust, sharing the same Curve25519 key-management API.

Bottom line: Treat .agvv as a non-decryptable fully-automated extortion agent. Prevention, segmentation, and verified off-line backups are the only reliable escape hatch.