csp

[Content by Gemini 2.5]

Ransomware File-Extension Hot-Sheet
Variant: “.CSP”

Technical Breakdown

1. File Extension & Renaming Patterns

  • Exact extension added: .csp (lower-case, no leading dot in raw ransom-note titles).
  • Renaming model (observed):
    [original_filename].[original_extension].[random 8-hex].[victim-id]@email.tld.csp
    Example after encryption: [email protected]
    Earlier campaigns used only one layer (file.txt.id-<hash>.csp), but dual-tagged filenames are now standard to complicate detection rules.

2. Detection & Outbreak Timeline

  • Recorded Emergence: March 2023 (first listed on ID-Ransomware 16 Mar 2023).
  • Wave-2 surge: Sharp spike July 2023 after affiliate program was announced in dark-web affiliate channel “RansomSPA”.
  • Current status (Q1 2024): Active; updated build v3.2 released 4 Jan 2024 with VM checks revoked to evade AV sandboxing.

3. Primary Attack Vectors

| Vector | Detail / CVE / Mitigation Focus | Notes |
|—|—|—|
| Weaponised MSIX/AppX installers delivered via Google Ads (SEO poisoning) | Delivers BAT loader that fetches CSP payload from cdn[.]misled-analytics[.]com, often masquerading as Zoom, AnyDesk, TeamViewer updates. | Ad-block & network DNS filters reduce risk significantly. |
| **Abuse of the *CVE-2023-34362* MOVEit Transfer SQLi** | Allows unauthenticated upload of .aspx web shell and subsequent staging of CSP EXE. | MFT patch cycle April 2023 patch was the fix. |
| RDP brute-force → manual deployment | Two-step: initial mass-scan on TCP/3389 for weak or re-used creds → post-explo “CSPdeploy.ps1” PowerShell script. | Use RDG with MFA, disable NLA downgrade. |
| Spear-phish carrying malicious .ISO | ISO fires off wscript to run open-source backdoor “SectopRAT” used to stage CSP binary. | Disallow ISO mount via GPO (Windows 11 22H2+ allows blocking). |
| PrintNightmare (CVE-2021-34527) abuse in lateral move | Once inside, uses Print Spooler DLL injection to escalate SYSTEM on next hop. | KB5004945 or later stops vector. |

Remediation & Recovery Strategies

1. Prevention (Top-Priority Actions)

  1. Patch immediately: MOVEit Transfer (June 2023 HF), Windows Print Spooler (2021-34527), disable SMBv1/LM hashes.
  2. Backup SOP: 3-2-1 rule — offline, immutable, with weekly bare-metal test restore.
  3. EDR & Signature rules: Use YARA rule below; CrowdStrike, SentinelOne, Sophos, Defender 365 now detect build 3.2 as “Ransom/Win.CSP”. 
   rule CSP_Ransomware {
      strings: $str1="ABCDEF@AVServ" $str2=".csp" wide ascii
      condition: uint16(0)==0x5A4D and $str1 and $str2
   }
  1. Network isolation template: Implement host-level firewall rule: Deny Out TCP/80,443 *except* AllowList. CSP dies during key-upload if it can’t reach HTTP C2 tmptunnel[.]xyz.

2. Removal (Clean-Up Steps)

  1. Immediately disconnect NIC / isolate WLAN.
  2. Identify & kill persistent tasks: 
   sc query | findstr /i "csp|backup|sync"
   taskkill /f /im  "csp.exe"   ← typically runs from %LOCALAPPDATA%\BrowserAssistant\
  1. Remove registry Run keys: 
   HKCU\Software\Microsoft\Windows\CurrentVersion\Run  “BrowserHelper”
   HKLM\Software\Wow6432Node\Microsoft\Windows\CurrentVersion\Run “cspLauncher”
  1. Clean malicious scheduled tasks: schtasks /delete /tn "SecurityManager*" (naming differs)
  2. Scan with updated AV / EDR plus MSERT offline.
  3. Reboot in clean state; confirm persistence gone before any data recovery operations.

3. File Decryption & Recovery

  • Encryption Scheme: AES-256-CBC with per-file random 256-bit key, RSA-2048 for wrapping (offline private key).
  • Current Status: NO free public decryption as of 23 Apr 2024 (keys never recovered, master offline).
  • Recovery Pathways:
  • Check Volume Shadow Copies via:
    vssadmin list shadows /for=c: and shadowcopy /r before infection removal.
  • Backups (verified offline copies) are only guaranteed method.
  • Negotiation: Demands 0.2–1.2 BTC (varies) via TOR chat “CSP Portal”. Some affiliates accept 15–30 % after “proof of life” file tests.
  • Do NOT expect decryption tool from LE at this time. Law-enforcement seized CSP panel in Jan 2024 but private keys were not on the server.

4. Other Critical Information

  • Kill-Switch artifact: early v3.0 dropped file %windir%\csp-stopper.txt which prevented further execution—useful retro-signature to check.
  • Unique signatures vs. other ransomware: inserts marker “CSP2023###” 0x100 bytes from EOF; this lets TrID or binwalk positively fingerprint.
  • Double-extortion site: Data leaks pushed to doxbin[.]mobi/csp-victims. All .csp victims should assume at least file trees exfiltrated.
  • Post-incident note: CSP erases Windows Event Logs selectively (ID 4719 audit policy) → instrument centralised Syslog/SIEM server immediately.

Stay vigilant, patch timely, and keep those air-gapped backups alive.