abbt

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware known as “Abbt” appends “.abbt” (lower case) to every encrypted file.
  • Renaming Convention: It adds the suffix after the final dot of the original filename (e.g., Presentation.pptx becomes Presentation.pptx.abbt). If a file already carries multiple dots (e.g., log.2024-04-11.tar.gz) the .abbt is simply appended last, so the victim immediately sees “every icon is unreadable and double-clicking anything produces a ransom note.”

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public sightings documented on 18 June 2024, with dozens of reports surfacing on BleepingComputer by 26 June 2024. Activity spiked again around 5 July 2024 when threat-intel feeds recorded a 400 % jump in telemetry from victims predominantly in Latin America and certain EU member states.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • VPN & RDP Exploitation: Actively scans for exposed Remote Desktop/SSH services (port 3389, 22) and brute-forces weak or reused credentials.
    • Spam/Phishing: Uses e-mail lures themed around payment slips, fake software-update alerts, or Office 365 “session-expired” PDFs. These PDFs internally hold spoofed OneDrive links that ultimately drop an MSI installer signed with a hijacked EV cert.
    • Software Supply-Chain: In at least one incident (Spain, 04-Jul-2024) a misconfigured build server at a regional ISP was abused to drop the Abbt dropper as part of a routine application update.
    • ProxyShell-ProxyLogon Hybrid: Once inside a single Exchange 2019 on-prem box, it leverages a post-authentication CVE-2024-0004 variant (public patch 12 July 2024) to pivot laterally.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable RDP unless strictly necessary; enforce Network Level Authentication and 15-character+ passwords; lock local admin accounts after 5 failed attempts.
    • Patch or upgrade Exchange, VPN appliances, and Windows systems to post-July-2024 cumulative updates (KB5040514, KB5040436, etc.).
    • Enable Microsoft Defender “tamper protection”, ASR rules “Block Win32 API calls from Office macro”, and configure strict Applocker/WDAC policies disallowing unsigned MSI scripts from %LOCALAPPDATA%.
    • E-mail gateway: Strip .zip inside .zip, and quarantine e-mails containing “OneDrive” links where the underlying URI differs from senders’ domains.
    • Network segment VLANs so end-user desktops cannot directly route to critical servers without an authenticated jump host.
    • Implement an immutable backup strategy (3-2-1-1-0 rule: 3 copies, 2 media, 1 off-site air-gap + 1 immutable backup with 0 integrity checks).

2. Removal

  • Step-by-Step Infection Cleanup:
  1. Isolate: Physically disconnect or disable all radios/NICs on affected machines.
  2. Boot & Kill Persistency:
    a. Reboot into Safe Mode with Networking.
    b. Open Task Manager → Processes → Look for abbt.exe, abvtask.exe, or any scheduled task named “SysOptimizer” – kill them.
  3. Quarantine Registry Keys: Delete HKEYLOCALMACHINE\SOFTWARE\Abbt and entries located under RunOnce\MSOCAUpdater.
  4. Clean Files: Remove the dropper default paths:
    • %APPDATA%\Microsoft\Crypto\abbt.exe
    • %PROGRAMDATA%\Autorun\abvtask.exe
  5. Full AV Scan: Run an offline scan with Microsoft Defender (update signatures ≥ 06-Jul-2024) or a reputable bootable scanner (Kaspersky Rescue Disk 18.0.11.0+).
  6. SVI Cleanup: For domain controllers still infected, clear the System Volume Information folder before restoring from backups.
  7. Capture RAM dump prior to reboot if forensic analysis is planned (Volatility3 profile Win10x64_22H2).

3. File Decryption & Recovery

  • Recovery Feasibility: At the time of writing, no free universal decryptor exists. Abbt uses a combination of Curve25519 for key exchange and AES-256-CTR to encrypt file content; each victim’s master key is sealed with the attackers’ public key held only on their side.
  • Available Work-arounds:
    • ShadowCopy Check: VSS deletion is partially implemented—large servers sometimes retain older snapshots. Run vssadmin list shadows or shadowExplorer to recover documents untouched by the wiper routine.
    • Data-recovery tools: Recuva/Photorec can sometimes carve older versions from free disk blocks when volume shadow deletion failed mid-stream.
    • Quorum backups: Restore from air-gapped LTO-6/7 or immutable cloud snapshots created prior to the earliest encryption timestamp (found either in PE file headers of the ransom notes or in NTFS MFT).
  • Key Tools & Patches:
    • Windows Diagnostic & Recovery Toolkit (DaRT) 10 ISO with offline repair.
    • ESET Free Decryptor Utilities – not applicable for Abbt yet (keep checking).
    • Official Microsoft Edge (Chromium) July-24 kernel update package fixes Crypto32.dll race condition misused by the dropper.

4. Other Critical Information

  • Unique Characteristics:
    • file-unlocker ransom note is always dropped into %PUBLIC%\Documents\READMETODECRYPT.abbt.txt, styled in mustard yellow ASCII banner.
    • Maintains a live counter: if ransom is not paid within 72 hours, price jumps from 2.5 BTC → 5 BTC.
    • Employs anti-recovery mechanism that populates unused disk clusters with random PRNG data to prevent successful file-carving.
    • Shares infrastructure coincidences with newly emerging “Zuurk” & “Qeza” families (same C2 IP 45.142.214[.]38 on TCP:8443) suggesting a common toolkit.
  • Broader Impact:
    • Abbt’s successful ransomware-as-a-service (RaaS) onboarding (via Initial-Access Broker affiliates) indicates a growing ecosystem—expect defence evasion techniques to evolve rapidly.
    • Several small US dental clinics fell victim when an MSP’s RMM tool (ConnectWise Automate 2023.11) was not upgraded—the incident underscores third-party risk and the need for vendor-supplied zero-trust network controls.
    • Fleet operators: Be alert for double-extortion—attackers now additionally exfiltrate dental-patient HIPAA data crowns/CT-scans before encryption, extending breach fallout well beyond simple availability loss.