[asterisk-users] Is there a need to secure RTP ports?

[Sebastian Arcus]

I have an Asterisk server with one SIP trunk to a SIP provider. As my 
server registers with the SIP provider, I don't have any SIP ports open 
at my end to the Internet. However, I have the RTP ports open (as SIP 
has some trouble with my NAT). My question is - what are the 
vulnerabilities in this scenario at my end? I suppose some 
man-in-the-middle or eavesdropping  attack is always a possibility - but 
that aside, is there anything that will attack RTP ports on Asterisk 
when there are no SIP ports open? I was looking into installing fail2ban 
- until I realised that there is no SIP port exposed for an attacker to 
poke at.

Searching on Google for "secure RTP ports" keeps on bringing up results 
about SRTP - which is not exactly the answer to my question.

Thank you