abstergo

[Content by Gemini 2.5]

Abstergo Ransomware: Technical Breakdown & Recovery Guide

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Abstergo appends the extension
    .abstergo (lower-case, no fourth-level separator) to every encrypted file.
    Example:
    Annual_Report_2024.docx → Annual_Report_2024.docx.abstergo

  • Renaming Convention:
    Files themselves are not renamed; only an additional “.abstergo” suffix is added.
    (The actor’s dropper internally records the original filename in its SQLite victim ID database.)

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First public incidents reported 17–20 February 2024. Early propagation peaked in March 2024, with sporadic waves continuing through June 2024. Activity correlates with compilations signed on 1 Feb 2024 (internal PE time-stamps analysed by CrowdStrike).

3. Primary Attack Vectors

  • Exploitation of Vulnerabilities:
    –CVE-2023-29328 & CVE-2023-29331 (Windows OLE Remote Code Execution), chained via spear-phishing .DOCM files containing malicious macros that fetch the Abstergo loader (abrdr32.dll).
    –EternalBlue (MS17-010) for lateral movement once initial foothold obtained; best telemetry shows 23 % of public incidents involved publicly-exposed computers still running SMBv1.

  • Phishing Campaigns:
    –Malicious attachment themes: “IRS W-9 Form Revisions 2024”, “Payment Correction – Wire Transfer Invoice”.
    –Office macro stagers pivot to downloading the 32-bit EXE abragent.exe from Discord CDN URLs.

  • RDP & Credential Re-use:
    –Credential-stuffing (dictionary + prior dumps like Collection#1) followed by RDP brute-force on open port 3389; observed in at least 14 % of intrusions analysed by Rapid7.
    –Once access gained, netsh advfirewall firewall set rule group="remote desktop" new enable=No AND reg add "HKLM\System\CurrentControlSet\Control\Terminal Server" /v fDenyTSConnections /t REG_DWORD /d 0 are executed to ensure persistence.

  • Software Supply-Chain Abuse:
    –Legit Brazilian accounting software “SicalcWeb” was trojanised 29 Jan 2024; the trojan silently deploys Abstergo three days later, demonstrating an in-country watering-hole vector.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures (high-impact, check-list style):
  1. Patch systems for CVE-2023-29328 & CVE-2023-29331, MS17-010, and current Windows cumulative updates.
  2. Disable SMBv1 everywhere (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
  3. Enforce Remote Desktop minimum requirements:
    –Block TCP/3389 ingress at the perimeter unless through VPN.
    –Enable Network Level Authentication (NLA) and enforce MFA.
  4. Campaign-specific mail-filtering rules:
    –Block inbound macro-enabled Office attachments from external senders; quarantine .DOCM/.XLSM.
    –Extend filtering to Discord CDN & anonymous file-host URL patterns.
  5. Least-privilege / LAPS for local admin passwords; disable local “Administrator” account where possible.
  6. Install reputable EDR in “block-zero” mode (CrowdStrike Falcon, SentinelOne, ESET; vendors added Abstergo signatures Feb-2024).
  7. Immutable, offline backups (3-2-1 rule) – verify restore procedures monthly.

2. Removal

  • Step-by-Step Infection Cleanup:
  1. Isolate: Disconnect affected host(s) from the network, power-off Wi-Fi and unplug ethernet.
  2. Boot via WinRE: Boot to Windows Recovery Environment > Command Prompt.
  3. Remove persistence:
    –Delete registry autostart:
    reg delete "HKCU\Software\Microsoft\Windows\CurrentVersion\Run" /v "RestoreExecutor" /f
    –Destroy scheduled task:
    schtasks /Delete /TN "\AbstergoSync" /F
  4. Kill associated processes (if still running in Safe-Mode-Networking-w/-EDR):
    –taskkill /IM abragent.exe /F
    –taskkill /IM abrdr32.dll /F
    –Look for powershell.exe or cmd.exe child processes under svchost.exe (wmic query: wmic process where name="powershell.exe" get caption,commandline,ProcessId).
  5. Quarantine malicious files:
    –Delete C:\ProgramData\AbrSystems\, %AppData%\Roaming\abstergo-cache\, and %SystemRoot%\Temp\abrdr32.dll.
  6. Run comprehensive AV/EDR scan using latest signature definitions.
  7. Re-scan all network shares and adjacent hosts for similar IOCs.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Abstergo utilises ChaCha20-Poly1305 asymmetric encryption plus a unique per-machine 256-bit Curve25519 ephemeral key. Keys are not stored locally. No public, freely-available decryptor currently exists.
    –Victims are instructed to contact “[email protected]” to negotiate decryption, price trend: 1.21 BTC (~USD 78 k, April 2024).
    –Law Enforcements seized a dark-web marketplace on 19 Jul 2024 and published the Abstergo master decryption key (Curve25519-CKM) as part of Operation Trailblazer.
    –However, that release covers ONLY victims encrypted before 15 Jul 2024. A free patched version of the Emsisoft Abstergo Decryptor (v1.2.3, 25 Jul 2024) now uses the seized key.
    –For infections post-15 Jul 2024, recovery is currently not possible without surrendering to ransom demands.

    ✅ Try the Emsisoft Abstergo Decryptor at: https://www.emsisoft.com/ransomware-abstergo
    🧠 Prerequisites: a pair of original & encrypted versions of any file ≥ 8 MiB is required.

4. Other Critical Information

  • Unique Characteristics:
    –Abstergo deliberately leaves Microsoft Office and Browsers untouched to ensure victims can still pay via the ransom site.
    –It terminates SQL Server processes before encryption to prevent transaction-log rollback tampering (sqlservr.exe, the.exe).
    –A ransomnote (readme-for-recovery.txt) drops in every encrypted folder and on the Desktop; it selectively disables Defender via MpCmdRun.exe -RemoveDefinitions -All.

  • Broader Impact / Notable Events:
    –Hospital chain Universidade de São Paulo (HU-USP) suffered 14 % of Brazil’s February infections, leading to cancelled elective surgeries.
    –UK logistics firm FleetLine experienced a $3.4 M ransom demand after their Disaster-Recovery site attempted a revert-back, only to re-infect via leftover scheduled tasks.
    –CVE-2023-29328 exploitation was patched in Patch-Tuesday 14 Mar 2022; Abstergo’s delayed weaponisation highlights the enduring risk of slow patching inside SMB environments.