alert http $EXTERNAL_NET any -> $HTTP_SERVERS any (msg:"ET WEB_SERVER Possible XXE SYSTEM ENTITY in POST BODY."; flow:established,to_server; content:"ENTITY"; nocase; pcre:"/^\s+?[^\s\>]+?\s+?SYSTEM\s/Ri"; http.request_body; content:"DOCTYPE"; nocase; fast_pattern; content:"SYSTEM"; nocase; classtype:trojan-activity; sid:2018056; rev:4; metadata:created_at 2014_02_03, confidence Medium, signature_severity Major, updated_at 2020_09_22;)