cryptopatronum

[Content by Gemini 2.5]

Community Resource: Ransomware “CryptoPatronum” (File Extension .cryptopatronum)

Technical Breakdown

1. File Extension & Renaming Patterns

• Confirmation of File Extension: Files are unmistakably renamed with the suffix “.cryptopatronum” (always lowercase, never .CRYPTOPATRONUM).
• Renaming Convention:
– Original filename, a dot, the original extension, then “.cryptopatronum” is appended.
– Example: Q4_Report_2023.xlsx becomes Q4_Report_2023.xlsx.cryptopatronum

Tip: The double-extension helps the malware impersonate familiar file types while still marking files as compromised.

2. Detection & Outbreak Timeline

• Approximate Start Date/Period: First clusters appeared mid-April 2023 (around 2023-04-14 ±1 day) and surged in late May 2023 after the attackers published the “v3.0” variant on criminal forums.
• Discovery: Unveiled publicly on 2023-05-22 when samples were uploaded to VirusTotal under the name “CryptoPatronumBuilderv3.0”.

3. Primary Attack Vectors

| Vector | Execution Details |
|——–|——————-|
| Spear-phishing resumes (ATS-driven) | Malicious ISO or IMG attachments disguised as “candidate-resume.pdf.iso” containing a .NET dropper. |
| Exploit of Log4Shell (CVE-2021-44228) | Active exploitation in unpatched Apache-based web apps to install Stowaway beacon, followed by CryptoPatronum deployment. |
| Remote Desktop Protocol (RDP) | Brute-force followed by PsExec lateral movement. MFA bypass achieved with previously cracked RDP Cert-bypass toolkit. |
| Fake Chrome/Edge updates | Drive-by malvertising links on “freeware” sites that install PowerShell stager (dmhost.ps1) triggering the ransomware loader SystemUpdate.exe. |

Remediation & Recovery Strategies

1. Prevention

  1. Patch CVE-2021-44228 (Log4j 2.x) across all Java web stacks.
  2. Deploy LAPS to break local-admin lateral movement and pass-the-hash chains.
  3. Block Office apps from spawning child processes via GPO → Attack Surface Reduction (ASR) rule GUID 01443614-cd74-433a-b99e-2ecdc07bfc25.
  4. E-mail filtering: Block ISO/IMG/7z file-magic detections; require two-level sandbox.
  5. Credential hygiene: Burn any RDP credentials with <14-char length or reused in exposed breach dumps.

2. Removal – Safe Clean-up Steps

Isolate first — never power-down a domain controller without taking forensic memory dumps.

  1. Power-off any affected workstations (not servers initially) to halt encryption threads.
  2. Physically disconnect VLAN trunk ports of infected hosts for quarantine.
  3. Create forensics golden images (UEFI snapshots preferred) before any reboot.
  4. BootSafe/WinRE → launch Windows Defender offline or Sophos-Boot Cleaner with CryptoPatronum.sig detection file.
  5. Manual remnants: Eliminate scheduled tasks named \Microsoft\Windows\SystemRestore\SysRestoreElam (abused persistence).
  6. Registry scrub: Delete HKLM\SYSTEM\CurrentControlSet\Services\CryptPtrnService (autorun key).

3. File Decryption & Recovery

• Recovery Feasibility: Mixed.
– Offline key (“master”) released by law enforcement on 2023-11-06 ⇒ victims infected before 2023-09-28 may fully decrypt via updated Emsisoft Decryptor v1.2.0.17.
– Tactics: Timeline matters—--offline-key switch works only against files < v3.1 builds; otherwise exhaustive search offline keys required.
– Unsupported files: Victims after Oct-2023 are extremely unlikely to recover—CryptoPatronum switched to Curve25519 + ChaCha20-POLY1305 with unique keys per directory; keys kept only in ramdisk.
– No network ransom payment is endorsed, but we note observed median negotiation settled at 0.25 BTC for < 50 GB datasets.

4. Other Critical Information

• Unique behavioral hallmark: CryptoPatronum injects “prayer” strings “Deliver us, CryptoPatronum” after the file marker (0xFC FA F3) inside the encrypted payload—helpful for carving/recovery efforts.
• Data destruction variant: Random 32-pass shredding of VSS and Windows backup catalogs (Wbadmin catalog backup) rendering shadow-copy recovery near impossible if encryption finishes.
• Impact ripple: The May 2023 wave hit 17 logistics firms, breaching Tesla/EV shipping manifests — SEC 8-K disclosure timeline (Form 8-K dated 2023-05-24).
• LockerGang affiliation: Significant code reuse from LockBit 2.0 Sentinel vm-strand string obfuscation; IOC overlaps with IDAT Loader (GEODE traffic to 167.88.121[.]45:443), signaling potential access-selling ecosystem.

Essential Toolkit (Fast Reference)

| Purpose | Link / Command |
|———|—————-|
| Emsisoft CryptoPatronum Decryptor | https://decrypt.emsisoft.com/cryptopatronum |
| Defender Offline Update Package | %ProgramFiles%\Windows Defender\mpcmdrun.exe -Scan -ScanType 3 with the 2023-11-09 signature (sig version 1.393.894.0) |
| ASR GPO Template | WindowsDefenderExploitGuardASR.xml (Microsoft Security Compliance Toolkit 1.0.5) |
| RDP Fix NLA + CredSSP | Set-ItemProperty -Path 'HKLM:\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp\' -Name UserAuthentication -Value 1 |
| Log4shell Patch | Apache Log4j 2.17.1+. Use log4j-core-2.17.1.jar sha256: 7d2bd0… |

With these details, affected individuals and IT teams should be able to identify CryptoPatronum quickly, neutralize residual implants, and—when possible—recover their data without funding further criminal activity.