177
XDMCP
High RiskUDP — Remote Access
Port Overview
Port Number
177
Service Name
XDMCP
Transport Protocol
UDP
Category
Remote Access
Security Risk
High
Port Range
Well-Known (0-1023)
What is Port 177?
XDMCP (X Display Manager Control Protocol) allows X Window System display terminals to request a login session from a remote XDMCP server. Transmits credentials in cleartext.
UDP
Remote Access
Security Considerations
Port 177 (XDMCP) is classified as high risk. This port is a common target for automated scanning and brute-force attacks. If you must expose it, restrict access to known IP addresses.
Recommendation: Use firewall rules to whitelist trusted IPs. Enable rate limiting and intrusion detection.