Port 6601Microsoft Threat Management Gateway SSTP VPN

TCP 6601 is registered for Microsoft Threat Management Gateway's SSTP VPN service; SSTP carries PPP traffic through a TLS-protected connection.

inSecurity Remote Access

transport: tcp
in transit: encrypted
assignment: official
risk: 4/10
lookups: 0

also known as mstmg-sstp, SSTP, Microsoft SSTP

Technical Details

what runs on :6601

The registry associates TCP 6601 with Microsoft Threat Management Gateway SSTP. SSTP establishes a TLS-protected connection over TCP, then uses HTTP-based setup and SSTP control messages to carry PPP frames, typically for remote-access VPN connections. TCP 443 is the usual SSTP port; 6601 is not a generally recognized SSTP default, so confirm the application before assuming an open port is this service.

Security Information

exposure of :6601

risk score

4/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

security averages 3.0 across 409 ports — this one sits 1.0 above.

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

If this is an SSTP VPN listener, it is intended to provide remote access and should be exposed only when needed, with current TLS settings, strong authentication, and appropriate account protections. Encryption protects the tunnel in transit but does not eliminate risks from stolen credentials, vulnerable gateway software, or misconfiguration; no specific vulnerability follows from port 6601 itself.

Record

iana registry entry

port: :6601
service: Microsoft Threat Management Gateway SSTP VPN
transport: TCP
encryption: tls / encrypted
assignment: iana registered
risk: 4/10caution
category: Security Remote Access
usage: The assignment identifies Microsoft Threat Management Gateway SSTP, a VPN service using Microsoft's Secure Socket Tunneling Protocol. SSTP is more commonly associated with TCP 443, so an open 6601 listener may be a configured alternate endpoint rather than a common default.
lookups: 0rank 993
added: 2026-10-11
updated: 2026-10-11
references: IANA service name registry — port 6601

Something wrong?

This record is maintained by the engineers who use port 6601. 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 2026-10-11.

01edit any field on a page of its own
02a model checks it for accuracy and spam
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edit this record →back to the registry

Related Ports

all 409 in security →

the 8 most looked-up other ports in security — 409 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 :6601Microsoft Threat Management Gateway SSTP VPN

Technical Details

Security Information

Related Ports

Port 6601Microsoft Threat Management Gateway SSTP VPN