conficker

[Content by Gemini 2.5]

Important note: The word “Conficker” is the name of a well-known computer worm, not a ransomware family.
Conficker never alters document names with a new extension, nor does it encrypt user data.
To keep our resource internally consistent, the “file extension” heading is kept, but it should be interpreted as “Conficker leaves user data untouched (no new extension is applied)”.

Technical Breakdown:

1. File Extension & Renaming Patterns

• Confirmation of File Extension: Conficker does not append or change any file extensions. User documents (*.docx, *.xlsx, *.jpg, etc.) remain exactly as they were.
• Renaming Convention: None. The worm’s primary payload is propagation and remote-control, not data ransom.

2. Detection & Outbreak Timeline

• Approximate Start Date / Period: Initial sightings began on/around 21 October 2008 (variant “A”). Widespread outbreaks peaked between late 2008 – early 2009, with infection spikes recurring periodically until present day in under-patched networks.

3. Primary Attack Vectors

| Vector | Technical Details | Remediation Pivot |
|—|—|—|
| MS08-067 (SMB NetAPI32.dll) | Exploits un-patched Windows NT 5.x/6.x systems. Delivers DLL remotely (shellcode spawns a remote thread on port 445). | Patch MS08-067 |
| Removable media Autorun | Drops hidden DLL (autorun.inf, random name such as ykkz.dll) on USB keys. Re-spins on next insertion. | Disable AutoRun via GPO, enforce USB policy |
| Weak network shares | Brute-force against ADMIN$, IPC$, C$ via dictionary of common passwords. | Rename/Disable Administrator, complex passwords |
| Scheduled tasks & Service DLLs | Creates pseudo-randomly named Windows services (e.g., netsvcs) to survive reboot. | Review services against known-good baseline |

Remediation & Recovery Strategies:

1. Prevention

  1. Microsoft Security Bulletin MS08-067 patch – non-negotiable baseline for Windows XP SP2/3, Vista, 2003, 2008.
  2. Endpoint AV with current Conficker signatures (most vendors detect it as Worm:Win32/Conficker.*).
  3. Enforce strong, unique Administrator passwords via GPO (≥15 characters).
  4. Disable Autorun/Autoplay on all removable storage (registry/GPO: NoDriveTypeAutoRun=0xFF).
  5. Block TCP 139/445 inbound on edge/perimeter firewall to slow lateral spread.
  6. Segment networks; limit SMB/RDP exposure between departments with VLAN ACLs.
  7. Maintain comprehensive offline backups that cannot be overwritten by a worm (Conficker does not target backups, but good hygiene is preventive).

2. Removal (Step-by-Step)

  1. Isolate: Trap infected machines and USB devices off the production LAN (unplug, switch off Wi-Fi).
  2. Registry/GPO Immunize (pre-cleanup): Push the NoDriveTypeAutoRun registry entry cluster-wide to stop further USB infections.
  3. Boot into Safe Mode with Networking (or WinRE/KB-Linux) to remove resident DLL.
  4. Manual kill chain:
    a. Identify hidden service: sc query type= service state= all | findstr <random_name>
    b. Stop service: sc stop <random_name>
    c. Delete service: sc delete <random_name>
    d. Delete the worm DLL from System32 & %SystemRoot%\dllcache variants.
    e. Remove scheduled tasks under %SystemRoot%\Tasks.
  5. Automated removal tools (preferred):
    • Microsoft Malicious Software Removal Tool (MSRT) – March 2009 and later revisions detect and TP (Terminate-Process) Conficker services.
    • Trusted standalone scanners: ESET Conficker Removal Tool, Symantec W32.Downadup Removal Tool.
  6. Post-cleanup re-scan with updated AV to re-verify.
  7. Reconnect to LAN only after all peers are declared clean; otherwise the worm will immediately re-propagate.

3. File Decryption & Recovery

• Recovery Feasibility: Not applicable—Conficker does not encrypt user files, so no decryption is required.
• Essential Tools / Patches (all publicly available):

  • KB958644 (MS08-067 patch)
  • Microsoft MSRT – run monthly via WSUS
  • Updated AV signatures (all vendors supply Conficker definitions)

4. Other Critical Information

• Unique Characteristic: Creates a P2P command & control matrix (unique among worms); infected nodes consult daily pseudo-random sniffed top-level domains to fetch updates. This makes blocking domains via DNS dynamic.
• DNS Sinkhole effort: The Conficker Working Group (Universities + CERTs + AV companies) has been sinkholing the pseudo-random domains since 2009—interception still catches hundreds of thousands of unique IPs annually.
• Long-tail persistence: Low-patch embedded/industrial machines and legacy Windows (XP SP1) remain vectors 15 years later.
• Broader Impact: While not ransomware, Conficker’s bandwidth bloat, lateral movement, and ability to drop additional malware (including rogue AV scare-ware circa 2009 and later TrickBot/-Emotet dropper stubs) makes post-conficker auditing vital—a “silent” infection may later evolve into far more destructive payloads.

Key Take-away: Patch once, scan often, and eliminate the worm promptly—its defining trait is persistence, not encryption.