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Ports 1723 and 1701 · TCP

Ports 1723 and 1701: PPTP VPN (1701: L2TP)

Point-to-Point Tunneling Protocol, a VPN built into Windows since the 1990s. UDP 1701 is L2TP, normally wrapped in IPsec.

Protocol
TCP
On Windows
svchost.exe (Remote Access Connection Manager)
Risk if open to the internet
Medium

Seeing it on your PC

A built-in Windows VPN connection of the PPTP or L2TP type.

Should you block it?

PPTP's encryption is broken and should not be relied on. Move to IKEv2, WireGuard or OpenVPN if your provider offers them.

Check it on your PC

Run this in PowerShell to see what is using port 1723 right now, and which program owns it:

Get-NetTCPConnection -LocalPort 1723 -ErrorAction SilentlyContinue | Select-Object LocalAddress,LocalPort,RemoteAddress,RemotePort,State,@{n='Process';e={(Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName}}

No output means nothing is using the port at the moment. For every connection at once, paste netstat -ano into the netstat explainer.

Block it in Windows Firewall

In PowerShell run as administrator, this stops other computers from connecting to this port on your PC. It does not stop your own programs connecting out.

New-NetFirewallRule -DisplayName "Block inbound TCP 1723,1701" -Direction Inbound -Protocol TCP -LocalPort 1723,1701 -Action Block

Undo it with Remove-NetFirewallRule -DisplayName "Block inbound …", using the same name. If you depend on the service on your local network, this rule stops that too.