I have a bunch of calls that look something like this in the call logs.
2011-11-18 00:27:10SIP/xx.xx...unknown"unknown" sANSWERED13
How do I prevent this?
On FreePBX v14+, ensure "Allow Anonymous Inbound SIP Calls" and "Allow SIP Guests" are set to NO in Settings > Asterisk SIP Settings > General SIP Settings
. It is normally be set to this by default.