Internet-Security.com UDP port 153 details

UDP port 153 is used by the Simple Gateway Monitoring Protocol (SGMP).
SGMP (RFC 1028) was implemented on early IP routers/gateways as a precursor to SNMP and can still be found on some legacy network devices exposing an SGMP agent on UDP/153.
Because SGMP has little or no authentication and is obsolete, attackers sometimes scan this port for reconnaissance or information disclosure on misconfigured legacy routers.
No other common, modern protocols or applications are known to legitimately use UDP/153.

UDP 153