Please advise did upgrading to 3.5.5.1 stop these calls?

If not, where now?

For the record, I'm not experiencing the problem, but am conceded a bug may exist that could be exploited.

Iain

I have not upgraded the firmware, but Draytek are fully aware, and are still investigating. They monitored the router for a while but detected no further attempts to access it. External registration was turned off, and given that the router is in a secure cabinet, the problem has gone away, so it wasn't a cleaner plugging an analog phone in at night or anything like that!

I cannot use this client in any way as a guinea pig, as they are trialling one 350 phone on the 2820 as a prelude to a large move over to voip, and any further ag would kill the deal. I am confident that if there IS a hole, then Draytek will find it and plug it.

HTH

Thanks for the update. Let's hope something happens that gives us a solid answer, be it a bug or someone managing to get access....
Iain