TCP 6666
Synopsis
- Internet Relay Chat (IRC): Many IRC servers expose a cleartext listener on TCP 6666 (alongside 6665, 6667–6669).
- Examples include UnrealIRCd, InspIRCd, ircd-hybrid, and Ergo; public networks such as Libera.Chat and EFnet commonly accept client connections on 6666 as an alternative to 6667 (TLS is typically on 6697).
- IRC bouncers/services: ZNC is often configured to present a client port on 6666 for plaintext connections.
- Security note: Because 6666 is a common IRC port, several IRC-based botnets/malware (e.g., Kaiten/Tsunami and Agobot/Phatbot variants) have used it for command-and-control traffic.
Observed activity
Last 30 days
Detailed chart