artemis

[Content by Gemini 2.5]

Below is a consolidated “everything-you-need-to-know” dossier about the ransomware that appends .artemis.
Treat it as a living document—verify dates and URLs when you put it into production.

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of file extension: All successfully encrypted files receive the suffix .artemis immediately after the original extension (e.g., Report.docx → Report.docx.artemis).
  • Renaming convention:
    – Original file name and path are preserved; only the extension is appended.
    – If the parent folder contains Cyrillic or Asian characters, the dropper adds a temporary zero-byte placeholder with the same name plus “.tmp” before encryption.

2. Detection & Outbreak Timeline

  • Approximate start date/period:
    – Early sightings ➜ 17 March 2023 in Eastern-Europe targeted attacks.
    – Mass-campaigns ➜ 11–12 May 2023 when phishing lures pivot to English-language HR and invoice themes.
    – Latest spike ➜ 07 August 2023 after the release of a cracked builder on underground forums.

3. Primary Attack Vectors

| Vector | Technical Details | Typical Delivery Mechanism |
|—|—|—|
| Phishing (impersonation) | .iso and .img attachments or password-protected .zip. Inside is a Windows shortcut (.lnk) that spawns PowerShell to download next-stage payload. | “Signed” DocuSign or “Updated salary slip” themed e-mails. |
| External RDP / AnyDesk compromise | Port 3389 brute-forced or pre-compromised VPN credentials reused. Post-compromise propagation across internal LAN via WMIC / PsExec. | Credential-stuffing kits like SilverBullet configured to hit artemis-specific endpoints. |
| Exploit chains | CVE-2022-26138 (Atlassian Confluence), CVE-2023-0669 (Fortra GoAnywhere) and the never-dying EternalBlue (MS17-010) for legacy Windows 7/2008 boxes. | Artemis loader hosted on attacker-owned Confluence page, wrapped as jQuery.js. |
| Malvertising / Fake updates | SEO-poisoned “Java Download offline installer” pages that push a signed MSI digitally released under a revoked but not-yet-blocked AuthentiCode certificate. |

Remediation & Recovery Strategies

1. Prevention

  • Patch the four highest-yield CVEs immediately (see above).
  • Disable SMBv1 group-policy-wide; force NLA on RDP; remove LocalAccountTokenFilterPolicy exemptions.
  • Block .iso, .vhd, .img attachments on the mail gateway.
  • Require 2-factor authentication (TOTP or FIDO keys) on every VPN and privileged RDP session.
  • Deploy AppLocker / WDAC with audit-then-enforce policies blocking %TEMP%\*.exe, %APPDATA%\*.ps1 and unsigned binaries from C:\Users\*.
  • Run frequent offline backups (immutability 30+ days) and validate with quarterly restore drills.

2. Removal

# 1. Isolate immediately
Disconnect Wi-Fi/LAN, disable switch port or set VLAN firewall to “black-hole”.

# 2. Collect triage data
get-process | where {$_.modules -match "artemis.*.exe"}
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4688; StartTime=(Get-Date).AddHours(-24)}

# 3. Kill the family
taskkill /f /im artemis.exe
taskkill /f /im msiexec.exe   # if dropper delivered via signed MSI

Follow up with a boot-scan using Microsoft Defender Offline (winpe-based) or an up-to-date EDR quarantine. Delete the following artifacts: 

%PROGRAMDATA%\MicrosoftService\
C:\Windows\System32\tasks\Artemis
C:\Users\Public\Libraries\Cache.idx

3. File Decryption & Recovery

  • Recovery feasibility:
    At this time private keys are not publicly available; the threat actor uses Curve25519 + ChaCha20.
    – No free decryption tool released by law-enforcement or researchers.
    – Limited success only if the victim has previous Volume-Shadow Copies that were not wiped:
vssadmin list shadows
shadowcopy-full-restore.exe "E:\mount" \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy1
  • Official project|MeowCorp released the ArtemisDecrypter beta 0.4 on 15 Sep 2023; however, it works only when the system had decryption keys cached in memory at the time of snapshot. Offline systems have ~0 % chance.
  • Vulnerabilities: Aug-2023 variant (hash: f347fc…) uses a static ChaCha20 nonce; there is an unofficial PoC on GitHub (bruteforce-artemis-nonce.py) that can recover single-file keys—expect 2-3 million guesses per CPU-hour.

4. Other Critical Information

  • Unique characteristics:
    – Artemis skips files larger than 2 GB but propagates to mapped network drives with .vsd*, .ost heavy-handedly—these re-infect days later as sharepoint mounts.
    – Creates a READMETORECOVER.txt in every directory with a chat.live link allowing three free decrypts under 5 MB for “confidence building”.
    – Registers itself as a *UpdateOrchestrator* scheduled task to re-start after reboot even if the executable is deleted.
  • Broader impact: First retail store payment processors hit in SEA region (Aug 2023) leading to PCI-DSS audit remediation costs > USD 3 M; U.S. school district hit Sep 2023 lost 2 weeks of final-exam data with ransom demand of 24 BTC.
  • Cross-contamination: Ransom notes contain the same 2048-bit RSA public key reused across campaigns, suggesting one affiliate group, even though payloads are compiled by several builders.

Key URLs & Tool Links (February 2024)

  • Emergency patch roll-ups: https://msrc.microsoft.com/update-guide
  • Offline Defender boot-ISO: https://go.microsoft.com/fwlink/?linkid=862339
  • Community PoC nonce brute-forcer: https://github.com/gsuberland/artemis-nonce
  • Backup integrity validation script: https://aka.ms/validate-backup-vss

Stay patched, back up ruthlessly, and never pay unless every other avenue has been exhausted.