alert tcp $EXTERNAL_NET any -> $HOME_NET 22 (msg:"ET SCAN Potential SSH Scan"; flow:to_server; flags:S,12; threshold:type both, track by_src, count 5, seconds 120; reference:url,en.wikipedia.org/wiki/Brute_force_attack; classtype:attempted-recon; sid:2001219; rev:20; metadata:created_at 2010_07_30, confidence Medium, signature_severity Informational, updated_at 2019_07_26;)