alert tcp $HOME_NET any -> $EXTERNAL_NET 1863 (msg:"GPL CHAT MSN login attempt"; flow:to_server,established; content:"USR "; depth:4; nocase; content:" TWN "; distance:1; nocase; threshold:type limit, track by_src, count 1, seconds 60; classtype:policy-violation; sid:2101991; rev:3; metadata:created_at 2010_09_23, signature_severity Informational, updated_at 2019_07_26;)