A PPTP VPN server — obsolete, cryptographically broken, and still everywhere on old routers.
PPTP splits itself in two: a TCP 1723 control connection that negotiates and tears down tunnels, and GRE (IP protocol 47) carrying the encapsulated PPP frames. RFC 2637 documents it, and Microsoft shipped it in every Windows since NT 4, which is why it lives on in consumer routers, older RRAS servers, and appliance firmware. Its security rests on MS-CHAP v2 and MPPE, and Microsoft itself issued Security Advisory 2743314 telling customers to stop using unencapsulated MS-CHAP v2 after the 2012 demonstrations that reduced it to a single DES key search. Microsoft has since deprecated PPTP in Windows Server RRAS.
Do not expose
A captured PPTP handshake yields the user's password hash to an offline attack that finishes in hours, so an internet-facing 1723 is a credential leak waiting to be collected — replace it with WireGuard, IKEv2, or OpenVPN.
$ nmap -p 1723 --script pptp-version TARGETSeen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.