TCP Port 20 – ftp-data
About TCP Port 20
Port 20 carries the IANA assignment for ftp-data. The IANA description reads: ‘FTP’. This port is referenced in 12 IDS rules and exhibits high malware activity in monitored traffic.
IDS Rule References
12 IDS / security rules reference TCP port 20. 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 2): command-and-control (10), trojan-activity (2).
Sample rule descriptions for TCP port 20:
- ET MALWARE Win32/Emotet CnC Activity (POST) M5
- ET MALWARE Win32/Emotet CnC Activity (POST) M6
- ET MALWARE Win32/Emotet CnC Activity (POST) M7
- ET MALWARE Win32/Emotet CnC Activity (POST) M8
- ET MALWARE Win32/Emotet CnC Activity (POST) M10
Malware Rule References
A large share of the IDS rules that reference this port are malware related.
12 of the 12 IDS rules that reference TCP port 20 are malware related. That describes detection coverage across the whole internet, not anything about your machine or your network.
Families observed (top 1): Emotet (12).
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), and MITRE ATT&CK (Apache 2.0).