TCP Port 666 – doom
About TCP Port 666
Port 666 is registered with the Internet Assigned Numbers Authority (IANA) for doom. The IANA description reads: ‘doom Id Software’. This port is referenced in 6 IDS rules and exhibits high malware activity in monitored traffic.
IDS Rule References
6 IDS / security rules reference TCP port 666. Treat that number as context, not a danger score. Many detection rules are written against groups of ports rather than one service, web ports especially, so common web alternate ports inherit large counts while genuinely sensitive services can show few rules or none. Presence in IDS rules does not mean traffic on this port is malicious.
Rule categories (top 3): trojan-activity (3), misc-activity (2), command-and-control (1).
Sample rule descriptions for TCP port 666:
- MALWARE-BACKDOOR SatansBackdoor.2.0.Beta
- MALWARE-BACKDOOR BackConstruction 2.1 Client FTP Open Request
- MALWARE-BACKDOOR BackConstruction 2.1 Server FTP Open Reply
- ET MALWARE ELF/BASHLITE CnC Activity (Response)
- ET MALWARE Win32/SuperBOT CnC Checkin
Malware Rule References
A large share of the IDS rules that reference this port are malware related.
6 of the 6 IDS rules that reference TCP port 666 are malware related. That describes detection coverage across the whole internet, not anything about your machine or your network.
Families observed (top 5): BackConstruction (2), ELF_BASHLITE (1), Reptile (1), SatansBackdoor.2.0.Beta (1), Win32_SuperBOT (1).
Data Sources
This information is compiled from: IANA Service Name and Transport Protocol Port Number Registry, Emerging Threats Open Ruleset (BSD 2-Clause / GPLv2 per SID range), Snort Community Rules (GPLv2), and MITRE ATT&CK (Apache 2.0).