Port 300TLS Secure Login Host Protocol (TACACSS)

Encrypted secure-login host protocol assigned to TCP port 300.

transport: tcp
in transit: encrypted
assignment: official
risk: 1/10
lookups: 0

also known as tacacss

Technical Details

what runs on :300

TLS Secure Login Host Protocol (TACACSS) is registered on port :300 over tcp to IESG, assigned July 2025. We don't have a technical write-up for it beyond the IANA registry entry.

In nmap's internet-wide scan data this port is found open rarely. What's listening is often not the registered service, so check before you assume.

find what's listening on :300

this machine

# linux
sudo ss -tlpn 'sport = :300'

# macos / bsd
sudo lsof -nP -i :300

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :300

another host

nmap -sV -p T:300 <host>

run it? the handshake, the implementations you meet in the wild and the flags that matter come from the engineers who do.

add technical details

Security Information

exposure of :300

risk score

1/ 10safe

routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.

security averages 3.1 across 377 ports — this one sits 2.1 below.

in transit

encrypted

payloads are protected on the wire

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp

every listening transport is another surface to filter at the edge

security overview

no security notes recorded for :300 yet

known exploits, hardening advice, what a compromise looks like — suggest an edit if you know its exposure.

Record

iana registry entry

port: :300
service: TLS Secure Login Host Protocol (TACACSS)
transport: TCP
encryption: tls / encrypted
assignment: iana registered
risk: 1/10safe
category: Security Network Services
usage: TCP port 300 is assigned to the TLS Secure Login Host Protocol, identified by the registry handle TACACSS. The assignment is registered to the IESG; no broader deployment or implementation details are established here.
lookups: 0rank 993
added: 2026-09-15
updated: 2026-09-15
references: IANA service name registry — port 300
RFC 9887

Something wrong?

This record is maintained by the engineers who use port 300. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-09-15.

01edit any field on a page of its own
02a model checks it for accuracy and spam
03clean and confident goes live immediately

edit this record →back to the registry

Related Ports

all 377 in security →

the 8 most looked-up other ports in security — 377 ports carry that label.

port	service	proto	category	risk	views
:8881	Atlasz Secure Server	TCP	Web Services	caution	67.6k
:443	HTTPS	TCPtls	Web Services	caution	65.9k
:8291	Winbox MikroTik Admin	TCP	Security	caution	62.9k
:3268	Microsoft Global Catalog (GC)	TCPUDP	Security	caution	54.6k
:135	Microsoft EPMAP	TCPUDP	Security	caution	51.9k
:3128	Squid Proxy HTTP	TCP	Web Services	caution	45.8k
:8080	HTTP Alternate	TCP	Web Services	caution	44.9k
:7000	Vuze HTTPS Tracker	TCPtls	Security	caution	28.9k

risk mix of the 8 listed

caution100%

2 of 8 encrypted

Port :300TLS Secure Login Host Protocol (TACACSS)

Technical Details

Security Information

Related Ports

Port 300TLS Secure Login Host Protocol (TACACSS)