[Freeswitch-users] Question about SIP security

I'm running FreeSWITCH version 1.0.6 on a box that is live on the internet, but is not yet in use by us. Over the last 48 hours, someone from an IP in China has been connected to our server. We observed about 36 Kbps of UDP traffic. According to the cdr-csv logs, it looks like they were sequentially dialing extension numbers. They were not able to get any calls through to termination, due to the nature of our system. I'm reasonably certain that I removed all the default accounts. What should I be looking for? Mike van Lammeren