I'm hosting a PPtP server on a ADSL line.

This morning, I noticed the following lines appearing in my interface list:
<pptp-0>
<pptp-1>

Screenshot:


These do not match any of my current secrets, when I remove them, they simply re-appear.
Resetting the router may cause an IP-change and force a disconnect, but first I want to analyze if I have a gap in my security.

How should I proceed?

These interfaces appear when client connects but is not yet authenticated.