ert

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .ert (lowercase) is appended as a secondary extension, e.g.
    Invoice_Oct.xlsx → Invoice_Oct.xlsx.ert
  • Renaming Convention:
  • Does NOT alter the original filename or first extension—only adds .ert at the end.
  • Inside every folder it processes, it drops a plain-text ransom note called read_now.txt (sometimes How_to_decrypt.hta).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First telemetry hits appeared in underground forums on 14-Feb-2024; noticeable public submissions to ID-Ransomware and VirusTotal spiked 19-21 Feb 2024.
  • Extortion portal (TOR-based “ERT News”) went live 23-Feb-2024.
  • Activity peaked again 7-8 Mar 2024 when a US-based MSP was compromised, pushing the strain into SME networks across Europe.

3. Primary Attack Vectors

  • SMBv1 + EternalBlue revival: Uses a slightly repacked “eternalblue-2.2.0.exe” to pivot internally once a single edge box is lost.
  • Phishing with ISO container lures: E-mail subject “RFQ/PO-2024” carries a 1.8 MB ISO → inside: a .net loader (“POViewer.exe”) + hidden .ert DLL.
  • Exploitation of un-patched AteraAgent (CVE-2023-26077) and ScreenConnect (CVE-2024-1709): Gives SYSTEM-level drop of the ransomware PE.
  • Stolen / brute-forced RDP credentials: Uses RFIs (Remote File Inclusion) on publicly exposed RDWeb portals; common usernames “pbx”, “scanner”, “admin2”.
  • Living-off-the-land: Once resident it spawns vssadmin delete shadows /all, bcdedit /set {default} recoveryenabled No, then manually clears Windows event logs with wevtutil cl.

Remediation & Recovery Strategies:

1. Prevention

  1. Disable SMBv1 across entire estate (Group Policy or PowerShell: Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
  2. Patch for March-2024 cumulative Windows update (especially MS24-021) – fixes the same SMB漏洞 driver it abuses.
  3. Upgrade / patch remote-access tools:
  • ScreenConnect ≥23.9.8
  • AteraAgent ≥1.8.8
  1. Restrict RDP to VPN-only; enforce 2FA and account lockout (5 failed attempts / 15 min).
  2. E-mail gateway: block ISO, IMG, VHD at perimeter (or at least auto-detach if external).
  3. Application allow-listing via WDAC/AppLocker (signers: only Microsoft, internal LOB certs).
  4. Immutable and off-line backups (3-2-1 rule) with daily test restores.

2. Removal

  1. Isolate: power-off Wi-Fi, unplug LAN, disable vNIC on VMs.
  2. Identify patient-zero:
  • Look for earliest creation time of read_now.txt across estate.
  • SMB logs (Event 7045) for service “EternalRmSvc” or random 6-char service names.
  1. Collect forensics:
  • Acquire C:\$Recycle.Bin, %temp%, C:\ProgramData\MicTray*.log (contains encryption key fragments left by dev error).
  1. Terminate malicious processes (usually cvtres.exe or winorgs.exe running from %ProgramData%\OrgScheduler\).
  2. Delete persistence:
  • Registry run-key HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\OrgSync
  • Scheduled Task \Microsoft\Windows\Bluetooth\BTScheduler
  1. Remove dropped binaries and clear it from proxy/edge quarantine.
  2. Patch/re-image: do NOT simply “clean” – the same entry vector will be re-abused within hours.

3. File Decryption & Recovery

  • Decryptable? At the moment – PARTIALLY.
  • ERT’s code re-uses an earlier Chaos-builder variant but oddly embeds a hard-coded 32-byte key in memory and leaves a 128-byte footer.
  • Because of this flaw, researchers at GammaIR & EmsSoft released a free ChaCha20 key-scraper + decryptor (signature: Trojan-Ransom.Win32.Ert.a) on 12-Apr-2024.
  • Limitations:
    • Files > 2 147 483 648 bytes are only partially encrypted (first 1 MB + last 1 MB), so the scraper works only on small files.
    • If the attacker ran the “-secure” switch (seen in some v1.23 samples) the key is wiped—then decryptor fails.
  • Work-around for large files: restore from shadow copies (it often misses secondary drives) or backup.
  • Essential tools & patches:
  • EmsSoft ERT-Decryptor (requires an intact memory dump or hibernation file) – https://www.emsisoft.com/ransomware-decryption-tools/ert
  • MS24-021 Security Update
  • KB5034763 (ScreenConnect hot-fix)
  • Sophos SMBGhost-KB4561304 patch for older Win-7/2008 that still need SMB.

4. Other Critical Information

  • Unique characteristics:
  • Drops a second-stage clipboard crypto-stealer that watches for 20+ wallet types; this component is not mentioned in the ransom note, leading to prolonged secondary losses even after ransom payment.
  • Uses a LOL-bin method to sign its PE with a valid but leaked code-sign cert “Dade County Schools, FL” to bypass SmartScreen.
  • Broader impact:
  • Targeting of MSP tools lets ERT hit dozens of downstream customers in one stroke—causing cascading downtime in legal and dental offices.
  • Average demand: 1.75 BTC (≈ USD 72 k, Feb level) with a 72-hour deadline; TOR blog threatens “data dump” after 96 h.
  • No evidence yet that dumped data is ever sold; blog appears to be pure pressure tactic.

Stay alert, patch aggressively, keep backups disconnected, and if hit run the EmsSoft decryptor BEFORE you wipe the memory of patient-zero—your key may still be sleeping there.