[asterisk-users] getting invites to rtp ports ??

[sean darcy]

I'm getting invites to very high ports every 30 seconds from a 
particular ip address:

Retransmitting #10 (NAT) to 5.199.133.128:52734:
SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 
0.0.0.0:52734;branch=z9hG4bK1207255353;received=5.199.133.128;rport=52734
From: <sip:37120116780191250 at 67.80.191.250>;tag=1872048972
To: <sip:3712011972592181418 at 67.80.191.250>;tag=as3a52e748
Call-ID: 1504207870-295758084-609228182
CSeq: 1 INVITE
.......
WARNING[150318]: chan_sip.c:4127 retrans_pkt: Timeout on 
1504207870-295758084-609228182...

I thought invites had to go to port 5060 or so. I don't understand why 
somebody (let's assume a bad guy) is trying ports above 50000.

sean