What are the best security advices you can give?
The following write-up provides good information on securing Asterisk installations:
Bryan, are you kidding ?
Did you see viewtopic.php?t=79350 ?
The best security advice is to do the exact opposite of what I specified in the post linked from my signature.
The “recipes” used can be found in variety of publications about asterisk (many including digium’s own)
As a resident of Huntsville, I’m obligated to say “Hide Yo Kids, Hide Yo Wife.”
Don’t expose Asterisk outside of your internal network. VPN. TLS & SRTP. Limit the hosts that can connect. Use good passwords.