edgel

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware commonly referred to as “EdgeLocker” appends the static, lower-case extension .edgel to every file it encrypts (e.g. Q4-Report.xlsx → Q4-Report.xlsx.edgel).
  • Renaming Convention: No prefix or random hex is added; only the extra 6-byte extension. Inside each folder the malware also drops a Unicode ransom note named RECOVER-FILES.TXT (hash varies by build, average size ≈ 2 kB).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: EdgeLocker (.edgel) was first uploaded to public malware repositories on 20 March 2021 and began to appear in victim help-forum posts the same week. A second, larger wave using an updated payload (v2.1) was observed throughout June 2021–August 2021 and continues to resurface sporadically via RDP brute-forcers.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    – Exploited RDP / VPN credentials – still the dominant entry point (credential stuffing, weak passwords, abandoned employee accounts).
    – Phishing with ISO / ZIP lures – messages themed as “customer support tickets” or “DHL invoices” lead to an ISO that contains the packed .NET loader.
    – SMB & WMI for lateral movement – after breaching one host the attacker manually disables Windows Firewall, then uses wmic process call create to push edgel.exe to every reachable workstation.
    – Exchange / unpatched OS exploits – several incident-response (IR) cases showed ProxyLogon (CVE-2021-26855) being used to plant the first-stage web-shell, which later downloaded edgel; however, RDP is still required for privilege-escalation and broad encryption.

Remediation & Recovery Strategies:

1. Prevention

  • Disable RDP on perimeter if non-essential; if required, limit to VPN + MFA + IP allow-list + max-2-attempt lock-out.
  • Enforce 14+ character, complex, non-reusable passwords for all admins and service accounts.
  • Patch Exchange (Mar 2021 roll-up), SMB (disabling SMBv1), Citrix ADC, and Fortinet VPNs; many EdgeLocker intrusions traced back to these CVEs.
  • Use application whitelisting (WDAC / AppLocker) to block %TEMP%\*.exe and %APPDATA%\<random-name>\edgel.exe.
  • Keep offline, versioned backups (3-2-1 rule). EdgeLocker deletes Volume Shadow Copies, so “online” Windows backups are erased.

2. Removal (High-level IR flow)

  1. Disconnect affected machine(s) from network; power-off is optional – usually not necessary.
  2. Collect triage data (MFT, $LogFile, AmCache, SRUM, Sysmon, RDP event-IDs 21/22).
  3. Boot into Safe-Mode-with-Networking (or mount disk offline) and run reputable AV/EDR (Microsoft Defender with Security-Intelligence ≥ 1.343.1xxx, Kaspersky, Sophos, CrowdStrike, etc.). EdgeLocker’s main binary is flagged generically as Trojan:MSIL/Ryzerlo.A and Ransom:MSIL/EdgeLock.
  4. Delete persistence mechanisms – Registry Run entry (HKCU\Software\Microsoft\Windows\CurrentVersion\Run\\syshelper) and scheduled task “MicrosoftEdgelService”.
  5. Reset all local administrator and domain credentials; assume compromise.
  6. Re-image the box or apply a clean backup; patch fully before restoring data.

3. File Decryption & Recovery

  • Recovery Feasibility: EdgeLocker uses RSA-2048 (OAEP-SHA1) to encrypt a per-victim AES-256 key that is then used in CFB mode to bulk-encrypt files. At time of writing, no flaw has been found in the cryptographic implementation, therefore no free decryptor exists.
  • Victims should check NoMoreRansom.org periodically; if a flaw is discovered, the decryptor will be published there under the name “edgel_decryptor.exe”.
  • Essential Tools/Patches to apply immediately:
    – KB5000871 (Exchange), KB5004442 (PrintNightmare), and cumulative patch for Windows SMA-dll (SMB).
    – Kaspersky RannohDecryptor (does NOT work for .edgel, listed only because victims often try it).
    – Free space wiper/secure delete utility to forensically wipe the remains of the malware once the system is rebuilt.

4. Other Critical Information

  • EdgeLocker contains a hard-coded kill-switch domain (e.g. tumbs.duckdns.org). Creating that DNS A-record pointing to 127.0.0.1 on the local resolver prevents encryption on new machines (a trick used by some IR teams to “vaccinate” during active incident).
  • The malware queries Windows locale; systems set to Russian, Belarusian, Ukrainian, or Kazakh are abandoned before encryption – likely to keep the actor out of CIS legal cross-hairs. Do NOT rely on this as protection.
  • Data-leak extortion: A subset of victims reported that a 7-zip archive of sensitive files was uploaded to mega.nz by the same operator immediately before the ransomware fire. Assume breach of confidentiality even if files are restored.
  • Wider impact: Because EdgeLocker often lands on an administrator session, it can reach and encrypt network-attached (NAS) storage, VMware ESXi datastores (by issuing vim-cmd vmsvc/snapshot.removeall then encrypting flat-vmdk), and SQL Server backups, making full recovery time-consuming and costly.

Bottom line: With no reliable decryption, the only path to resilience against .edgel is hardened credentials, prompt patching, restricted RDP, and—most importantly—off-site, immutable backups. Until researchers break EdgeLocker’s crypto, preparation beats incident response every time. Stay secure out there!