Layer7 regexp for SIP

Hello,

can someone help me with creating regexp expressions for filtering sip headers to block scanners and so on?
at linux it can be done like this

iptables -A INPUT -p udp -m udp --dport 5060 -m string --string "sip-scan" --algo bm -j logdrop

list of scanner agents like this: “sundayddr sipsak sip vicious friendly-scanner iWar sip-scan sipcli”

thanks in advance.