alert tcp $EXTERNAL_NET any -> $HOME_NET 5060 (msg:"ET SCAN SipCLI VOIP Scan - TCP"; flow:established,to_server; content:"|0D 0A|User-Agent|3A 20|sipcli/"; fast_pattern; threshold:type limit, count 1, seconds 60, track by_src; reference:url,www.yasinkaplan.com/SipCli/; classtype:attempted-recon; sid:2017161; rev:2; metadata:created_at 2013_07_17, confidence Medium, signature_severity Informational, updated_at 2019_10_08;)