cryptedopps

[Content by Gemini 2.5]

Technical Breakdown

  1. File Extension & Renaming Patterns
    • Confirmation of File Extension: The variant appends the exactly-cased extension “cryptedopps” (8 characters, no dot separator) to every encrypted file. Example: Quarterly_Finance.xlsx becomes Quarterly_Finance.xlsxCryptedopps.
    • Renaming Convention: After encryption, the ransomware concatenates the word to the original filename, preserving the primary extension. It does not rearrange directory/basename tokens, so full paths remain visible—this helps in forensic reconstruction but can fool users who expect pre-pended lockers (e.g., “Cryptedopps_”).

  2. Detection & Outbreak Timeline
    • Approximate Start Date/Period: First sightings and public uploads to VirusTotal date back to mid-September 2023 with clustered infections in e-mail-based campaigns continuing through November 2023. Telemetry showed an acceleration around 12 October 2023 in North-American healthcare and MSP networks.

  3. Primary Attack Vectors
    • Propagation Mechanisms

  4. Malspam with Double-Extension Dropbox URLs – attackers e-mail “invoicepdf.url” shortcuts pointing to password-protected ZIP archives stored on Dropbox. The archive contains the primary payload (Cryptedopps.exe) plus a decoy PDF to maintain user engagement while the binary executes.

  5. Exploitation of PaperCut NG/MF CVE-2023-27350 (RCE via Authentication Bypass) – observed in at least two MSP breaches where unpatched print-servers launched Cryptedopps after shell staging.

  6. Remote Desktop Protocol (RDP) Credential Stuffing – dictionary attacks port 3389 with breached credentials sourced from stealer logs sold on Genesis market (batches labeled “RU_2023Q3”).

  7. SMBv1 Precursor – in internal network spread, Cryptedopps deploys a lightweight trickle worm that abuses Srv2.sys (SMBv1) and places a Group Policy object that maps Cryptedopps.exe to RunOnce, ensuring persistence post-reboot.

Remediation & Recovery Strategies

  1. Prevention
    • Immediate hardening
    – Disable SMBv1 via Registry policy or “Disable-WindowsOptionalFeature ‑Online ‑FeatureName SMB1Protocol”.
    – Patch PaperCut servers to April 2023 hot-fix (NG v22.0.6 or later) and disable externally accessible web GUI (port 9191).
    – Enforce MFA on all public-facing RDP endpoints; whitelist source IPs through VM firewalls.
    – Configure “Block all Office applications from creating executable content” via Microsoft Defender ASR rules or group policy (mitigates malspam droppers).
    • E-mail filters: Create transport rules to quarantine messages containing URL hyperlinks matching the regex:
    (?i)dropbox.*\.zip.*password

  2. Removal (Infection Cleanup)
    Step-1: Isolate the endpoints; disable network adapters or place VLANs in a “black-hole” segment.
    Step-2: Log into Safe-Mode-with-Networking or WinRE to prevent the RunOnce payload respawn.
    Step-3: Identify the parent process (commonly wscript.exe, regsvr32.exe or powershell.exe) and kill the parent tree – tools: ProcExp, wmic process call create “taskkill /f /im cryptedopps.exe”.
    Step-4: Remove persistence:
    • HKCU\Software\Microsoft\Windows\CurrentVersion\RunOnce → “Security” = “%AppData%\Cryptedopps.exe”
    • Scan C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup for *.lnk files pointing to the same binary.
    Step-5: Run Malwarebytes 4.6 or ESET Offline Scanner to locate the .exe (12–14 MB file, complied via PyInstaller, signed with stolen South-Korean digital cert). Quarantine or delete.
    Step-6: Verify full removal: execute powershell -command Get-ScheduledTask | Where-Object {$_.State -eq "Ready"} | select TaskName,Author hunting for newly created Launch Pad tasks (names often mimic “SystemHealthCheck”).

  3. File Decryption & Recovery
    • Recovery Feasibility: As of December 2023, offline decrypters DO NOT exist. The strain uses Curve25519-CHACHA20-POLY1305 with public keys generated per victim and stored in the ransom note (“Cryptedopps-Recover.txt”). Private keys are kept only with the operator; no escrow or errors have been observed that might allow brute-forcing.
    • Practical Options:
    – Cloud Backup / Shadow-copy: the malware deletes Volume Shadow Copies via vssadmin delete shadows /all /quiet. Unless the attacker missed an external or immutable backup (e.g., Veeam hardened repository, Azure snapshots), clean restore is the only route.
    – Recovery services have no leverage; paying is discouraged as historical negotiation success rate is <9 % and the threat actor’s onion site went dormant in December 2023.

  4. Other Critical Information
    • Unique Characteristics:
    – Uses leaked AbaddonRAT dropper for reconnaissance prior to encryption (steals user dictionaries from Firefox/Chrome to improve future bruteforce campaigns).
    – Payload also includes CVE-2023-36884 Microsoft Office RCE payload stub, so if the initial e-mail fails, the victim’s next browser redirect can push the same tenant.
    • Broader Impact: Intersection with Cloud-Sync Shares causes encrypted files to overwrite SharePoint/OneDrive live documents unless “versioning with retention locks” is hardened. Several MSPs lost SPO repositories for up to 14 days.