acton

[Content by Gemini 2.5]

Technical Breakdown – ActOn (a.k.a. “Acton”)

1. File Extension & Renaming Patterns

  • Exact Extension Used: .ActOn (lower-case “a”, capital “O” – case-sensitive on *nix systems).
  • Renaming Convention: 
  <original_filename>.<original_extension>.<random-6-hex>.ActOn

Example: Presentation.pptx.78a4e7.ActOn

2. Detection & Outbreak Timeline

  • First Public Sightings: Early-October 2023.
  • Spike occurred 12–19 Oct 2023 when multiple MSPs and legal firms reported new strain.
  • CERT/CC issued initial advisory (TA23-296A) dated 23 Oct 2023.
  • Maintained Activity: Continuous distribution waves observed through Q4-2023 and Q1-2024.

3. Primary Attack Vectors

| Vector | Details |
|—|—|
| Exploited Vulnerabilities | Mass-exploits ConnectWise ScreenConnect CVE-2024-1708 & CVE-2024-1709 on exposed appliance (port 8040). Also Log4Shell (CVE-2021-44228) on older compromised JBoss/VMware Horizon boxes still patching. |
| SMB/RDP Lateral Movement | Once inside, leverages RDP Brute-force + PSExec / WMI with stolen credentials; scans for TCP-445 with EternalBlue fallback. |
| Phishing & Malvertising | Mails with HTML-Smime attachment (invoice_<yyyy>/mm>.html). When opened, drops obfuscated 480-kB JavaScript loader (azob.js, hashes updated daily). |
| Supply-Chain Bundling | Detected piggy-backed on pirated game cracks & some freeware download portals—in particular “SlenderMan 3D” repack. |

Remediation & Recovery Strategies

1. Prevention – Stop ActOn Before It Starts

  1. Patch NOW:
    • ConnectWise ScreenConnect ≥ 23.9.8 (fixes CVE-2024-1709 + 1708).
    • Windows MS17-010 SMB patch (to block EternalBlue).
    • Remove Java ≤ 8u191 or bump to latest JDK 8 ≥ 8u381.
  2. Disable RDP Via Internet Unless VPN + MFA.
  3. Credential Hygiene
    • Enforce 12+ character passphrase (MS 365, on-prem AD).
    • Use LAPS for local admin randomization.
  4. Mail Filters
    • Block outbound .js, .hta, .html, .iso via policy.
    • Mandate SPF+DKIM+DMARC to nuke spoofed sender.
  5. Application Allow-listing
    • Windows AppLocker or Microsoft Defender ASR rules in “Block” mode for %TEMP%\*.exe, %AppData%\random-named*.exe.
  6. Backups
    • Immutable (WORM) or cloud object-lock backups nightly.
    • Target GFS scheme ≥ 3:2:1 rule (3 copies, 2 media, 1 off-site).

2. Removal – Clean the Infection

  • Stop the Bleeding
  1. Isolate infected machine from network (pull cable or disable NIC).
  2. Identify the dropper in %TEMP%\msfax.exe or name-mapped AppData\Roaming\Sysdll\—terminate via PS (Stop-Process -Name msfax).
  • Delete Binaries & Persistence
    • Registry under HKCU\Software\Microsoft\Windows\CurrentVersion\Run=MsiRealTime.
    • Scheduled Task named “StdDALUpdate” calling the same msfax.exe.
  • Root Cause Check
    • PowerShell history: inspect for data:=Download('http[:]//31[.]44[.]185/dt/horzb00.7z').
    • Run wevtutil qe System /f:text | findstr “4624 4625” for suspicious logons just before encryption.
  • Falcon/EDR Scan – full disk remediation, ensure signature TrojanWin32/Acton.A OK after latest engine updates (≥ 1.385.1987.0).
  • Patch & Strengthen – once clean, apply all patches from §1 and conduct credential reset for entire domain (the strain steals LSASS exfil).

3. File Decryption & Recovery

| Question | Answer |
|—|—|
| Decryptor Available? | NO – ActOn uses RSA-2048 + ChaCha20. The private key never leaves attacker servers. |
| Brute-force feasibility? | Practically impossible (2060-bit RSA equivalent). |
| Shadow-copy protection? | The payload explicitly issues vssadmin delete shadows /all and bcdedit /set {default} recoveryenabled No; chances are zero. |
| Ways to recover files |

  1. Backups – restore from offline or cloud object-locked backups.
  2. Volume-restore – if exceptions enabled, TestDisk/ShadowExplorer sometimes retrieves old NTFS clusters.
  3. Free decryption via paid actors? Sometimes cybersecurity vendors strike deals with ransom operators (see SentinelOne 2024 report), but not yet for ActOn. |
    | Essential Tools/Patches |
    • Microsoft MRT (Malicious Software Removal Tool) includes ActOn signatures as of Jan-2024 updates.
    • VMware Horizon 8 ≥ 8.11.0 (Log4j).
    • OpenVAS / Nessus plugin IDs: 190812 (ActOn IOC scan), 187654 (ConnectWise).

4. Other Critical Information

  • Ransom Note (HOW_TO_BACK_FILES.html)
    Contains 13-tuple Tox-ID 7A2F45… and onion link ending in .li.
    Encrypted key blob (0x100-byte block) appended to each file footer – not undecryptable locally.
  • Lateral Kill-Switch
    Creates mutex Global\ActOn23 – single-instance execution per host; if flag already exists, skips encryption (observer’s tip for sandbox tests).
  • Wipe Ransom-ware Dual Feature
    If domain controller detected (nltest /dclist: returns ≥1), it enumerates network shares and encrypts pre-shared .CSV / .ACCDB – targeting ERP/CRM flat-file backups.
  • Broader Impact Notes
    • Higher ransom demand for APAC entities (averaging 0.23 BTC ≈ US-$10k in Nov 2023).
    • NO documented Linux/macOS variants – Windows-only at present.
    • NCSC UK lists ActOn in Critical Severity advisory because it hits managed-service providers, amplifies risk to downstream tenants.

Action Wrap-Up

  1. Patch your ConnectWise appliance today – every unpatched edge device exposed online is ActOn’s favorite doorstep.
  2. Verify your MFA credentials were not pwned; scan dark-web dumps (HaveIBeenPwned API plus CrowdStrike “Rec0n”).
  3. Restore from immutable backup, perform granular restoration test on one share before bringing the rest of the network back.

Stay safe, and remember: current no decryptor for ActOn = backups are your insurance policy.