asterisk hide version from nmap scan

I'm looking for methods (iptables rules, etc...) to prevent the asterisk version from showing on a nmap udp scan without closing (drop) the port. If I open it for some ip address, a nmap udp scan to port 5060 from this ip address can resolve the asterisk version(nmap -sU -sV -p 5060 <ipaddress>):

PORT     STATE  SERVICE VERSION
5060/udp open   sip     Asterisk PBX 1.8.13.0

Is there some way that only shows port 5060 open? Is it possible to hide this asterisk info or change it?

Solution

I think you can use pbx info by followin in sip.conf

useragent=SIPClient XXX

But actualy on my host that command show:

[root@pro-sip ~]# nmap -sU -sV -p 5060  78.47.XXX.XXX

Starting Nmap 4.11 ( http://www.insecure.org/nmap/ ) at 2012-12-05 22:35 UTC
Interesting ports on pro-sip.net (78.47.XXX.XXX):
PORT     STATE         SERVICE VERSION
5060/udp open|filtered sip

Nmap finished: 1 IP address (1 host up) scanned in 52.025 seconds

so maybe on your host it just find some issue and guess it is asterisk version XXX