demon

[Content by Gemini 2.5]

Comprehensive Guide on “Demon” Ransomware (File-Extension .demon)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .demon (lower-case, without further decoration).
  • Renaming Convention:
    Original path → <original_name>.<original_extension>.demon
    Example: Annual_Report_2024.xlsx becomes Annual_Report_2024.xlsx.demon

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First public sightings: mid-June 2021, with active global campaigns peaking between August-December 2021.
    Incremental new builds were still propagated throughout 2022 and resurfaced in 2024 Q1 via affiliate kits (RaaS).

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing payloads (.iso, .vhd, .lnk inside .zip email attachments) masquerading as invoices, job résumés, or COVID-tracker forms.
  2. RDP/SMB compromise – exposed RDP (3389) or SMB (445) harvested from Shodan lists, brute-forced or accessed via compromised credentials.
  3. ProxyLogon-Similar Exploits – chains CVE-2021-34473, CVE-2021-34523, CVE-2021-31207 against un-patched Microsoft Exchange servers to deliver backdoor cmd, then payload.
  4. Malspam campaigns beginning with a SmokeLoader or QakBot infection that fetches Demon binaries from a Discord CDN URL or temporary MEGA links.
  5. Software vulnerabilities – notably Confluence (CVE-2021-26084), SonicWall VPN (CVE-2021-20016), and Log4Shell (CVE-2021-44228) used for initial foothold.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
    • Patch immediately: Windows March 2020 SMB fix (MS17-010 retro-fixes included in every cumulative rollup), Exchange security updates released post-May 2021, Confluence, SonicWall, and Log4j library patches.
    • Segment networks and disable SMBv1 where possible.
    • Enforce MFA on all external RDP/VPN portals; disable RDP if not needed.
    • Email filtering: block .iso/.vhd/.lnk inside ZIP, strip macro Office docs by policy.
    • Endpoint protection with behavioral rules (look for *.demon writes, disable vssadmin.exe delete shadows).
    • Offline or immutable backups plus 3-2-1 rule.

2. Removal

  • Infection Cleanup – Quick Step List:
  1. Isolate the host from the network (physically or via NAC).
  2. Identify the running persistence path (%AppData%\Microsoft\UserDataSvc\userdtsvc.exe or similar random path).
  3. Boot into Safe Mode with Networking or Windows Recovery Environment.
  4. Run an on-demand scanner:
    – Microsoft Defender Offline (update first)
    – Kaspersky Rescue Disk or Bitdefender Rescue CD
    – SentinelOne ActiveEDR (if enterprise)
  5. Check scheduled tasks, services, and registry Run keys (HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run).
  6. Collect forensic images of affected drives before re-imaging.
  7. Wipe and reinstall OS (or, at minimum, restore pre-infection restore point taken offline).

3. File Decryption & Recovery

  • Recovery Feasibility:
    Demon generally uses an offline RSA-2048 key plus AES-256 session key (unique per victim). At this time there is no publicly available decryptor for the master key set—only a few early 2021 test builds have keys reversed by Avast, but those keys are not compatible with later affiliate campaigns.

  • Practical Recovery Paths:
    – Re-build from offline/encrypted backup created prior to infection.
    – Attempt file-carving (PhotoRec, R-Studio, Stellar, GetDataBack) on un-reallocated drive space if VSC or Shadow Copies were not wiped.
    – Always validate backups are malware-free before restore; Demon sometimes drops secondary payloads.

  • Essential Tools / Patches Recap:
    – Windows Update KB5006670+ (Exchange fixes)
    – Confluence 7.13+ or steps per Atlassian advisory
    – Log4j library 2.17.0+
    – Latest Defender engine & signature Microsoft KB2267602
    – CrowdStrike Falcon, SentinelOne, or Sophos IPS rules for “demon.exe detections”

4. Other Critical Information

  • Unique Characteristics:
    – Demon stores XOR-encrypted onion link in each ransom note (README_FOR_DECRYPT.txt dropped in every folder).
    – Contains VM-safeguard: if detects VMware Tools or VirtualBox drivers, it activates faster encryption routine and deletes itself.
    – In memory it dynamically builds DLL path strings and loads via RtlDecompressBuffer to evade YARA hooks.
    – Affiliate model (RaaS) so each actor can re-brand the toolkit, causing slight build variance—hash-tier does not alone guarantee original build.

  • Broader Impact:
    – Target overlaps with industrial control, healthcare, and legal verticals (affiliate group targeting).
    – Average ransom demand ~US $150 k in Monero (XMR) or ~US $400 k in BTC for SMB cases.
    – Historical precedent of triple extortion in later waves (DDoS threats + potential data auction on dark markets).

Stay vigilant: continuous monitoring, immutable backups, and up-to-date patches remain the most reliable defense against Demon ransomware reinfection.