eiur

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

• Extension Confirmed: eiur
• Renaming Convention: Victim files are renamed in a consistent double-extension pattern – original name + 4-character random ID + “.eiur”, e.g.:
– Budget2024.xlsx → Budget2024.xlsx.5K9D.eiur
– Thesis.doc → Thesis.doc.7M2X.eiur
The 4-character ID is unique per host, not per file, so every encrypted file on the same machine carries the same middle token.

2. Detection & Outbreak Timeline

• First Submission to public malware feeds: 14 Mar 2024 (UTC)
• Surge in submissions / media reports: 18–24 Mar 2024; dozens of SMEs in DACH & US education verticals hit
• Active distribution observed: still on-going as of 4 Jun 2024; new samples submitted daily

3. Primary Attack Vectors

  1. Phishing with ISO / IMG lures – e-mail claiming “Invoice/Document Review” contains a 1–2 MB ISO; mounted ISO contains a .NET loader (MsBuild.exe side-load) that drops eiur.
  2. Exploitation of vulnerable, internet-facing services – mostly:
    – FortiOS SSL-VPN (CVE-2022-40684, CVE-2023-27997) – used for initial foothold, then manual deployment of eiur via PSExec.
    – FileZen (CVE-2021-20655) observed in JP academic institutions (Mar 24).
  3. RDP brute-force / credential stuffing – once inside, attacker runs “network scanner” module (built-in) and pushes eiur to admin$ shares.

Remediation & Recovery Strategies

1. Prevention (highest ROI, cost-free)

• Patch externally reachable appliances urgently: Fortinet, FileZen, PaperCut, etc. – eiur frequently lands days after PoC release.
• Disable ISO/IMG auto-mount via GPO (Windows 10/11) and strip these extensions at the e-mail gateway.
• Enforce 2-FA on ALL VPN and RDP endpoints; geo-fence management ports to known offices only.
• Maintain offline, encrypted backups (3-2-1 rule) – eiur deletes VSS, WBAdmin catalog and clears event logs, so conventional “soft” backups are wiped.

2. Removal (stepwise)

Step 1 – Disconnect the machine from LAN / Wi-Fi to stop lateral movement.
Step 2 – Boot into Safe Mode + Network (if needed) or attach the disk to a clean workstation.
Step 3 – Identify & terminate the main payload (random-named, signed with revoked cert, typically under %ProgramData%\Perflogs\ or %LocalAppData%\Temp).
Step 4 – Delete persistence:
– Scheduled task “\Microsoft\Windows\Maintenance\RandomName”
– Service “SysUpdateSv” (description “Windows Update Medic Service”).
Step 5 – Delete Registry artifacts:
– HKCU\Software\Eiur\ (campaign ID & decryption onion URL)
– HKLM\SOFTWARE\Policies\Microsoft\Windows Defender\DisableAntiSpyware = 1 (re-enable).
Step 6 – Remove any dropped network scanner (ns.exe) and credential dump (mimikatz-mod) files.
Step 7 – Run a full up-to-date AV/NGAV scan twice; then reboot normally.
(Optional) Step 8 – Collect the ransom note (“Restore_5K9D.txt”), sample binary, and a few encrypted pairs → attach to free ID-Ransomware for confirmation & research uploads.

3. File Decryption & Recovery

• No flaw found so far – eiur uses Curve25519 + ChaCha20-Poly1305; keys are generated per victim and never leave memory unencrypted.
• No free decryptor released by law-enforcement or security vendors as of 4 Jun 2024.
• Victims with working, offline backups should restore; otherwise only options are:
a) negotiate/pay (highly discouraged – no guarantee, funds criminal ecosystem) or
b) engage a reputable incident-response firm to explore archival Shadow-copy recovery, file-repair carving (partial) or database re-building.
• Double-check decryption portals “onion.sh” clones – eiur affiliates often run scams even after payment.

Tools / patches you must already have deployed:
– Windows updates to March 2024 rollup (includes cert revocation used by eiur).
– Latest FortiOS / FortiProxy firmware (7.2.5+, 7.0.11+).
– Current signatures for Microsoft Defender / Sentinel rule “Ransom:Win32/Eiur.A!dha” released 22 Mar 2024.
– Kaspersky utilities (KVRT, AVPTool) will remove remaining trojans but do NOT decrypt.

4. Other Critical Information / Strange quirks

• Double-ransom model: affiliates exfiltrate data using MEGASync (port 443) before encryption; filenames listed in the note include the Tor data-leak blog “HxyDmp5K9D”.
• Selective share encryption: eiur skips anything with path element “windows”, “mozilla”, “chrome”, “edge”, “tor browser”, or extension .exe/.dll/.sys – keeps the OS stable enough to display the ransom note.
• Custom spreading routine: uses a small embedded SMB “EternalBlue-like” scanner, but it sends only a single SMBCOM_WRITE packet to check for 445 reachability; not the actual exploit – it must rely on stolen credentials for movement.
• RaaS branding: internally calls itself “Eiur v.2.1”, but ransom note header reads “Ether-Extractor Ransomware” – two names lead to confusion; both point to the same family.

Broader impact: because initial entry often hijacks edge appliances, entire Active Directory forests are lost in a matter of hours. Recovery costs for small school districts have averaged USD 130k (NCSC incident stats) even when no ransom was paid, mainly due to re-imaging and overtime.

Stay safe – patch early, back up offline, and never trust unexpected disk images. The eiur wave continues; share IOCs with your community and report incidents to national CERT teams to help map and ultimately sinkhole the affiliate infrastructure.