alert http $EXTERNAL_NET any -> $HTTP_SERVERS any (msg:"ET SCAN Simple Slowloris Flooder"; flow:established,to_server; threshold:type limit, track by_src, count 1, seconds 300; http.method; content:"POST"; http.header; content:"Content-length|3a 20|5235|0d 0a|"; fast_pattern; http.header_names; content:!"User-Agent|0d 0a|"; reference:url,www.imperva.com/docs/HII_Denial_of_Service_Attacks-Trends_Techniques_and_Technologies.pdf; classtype:web-application-attack; sid:2016033; rev:5; metadata:created_at 2012_12_14, confidence Medium, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_05_08;)