alert http $EXTERNAL_NET any -> $HOME_NET $HTTP_PORTS (msg:"ET SCAN HTTP HEAD invalid method case"; flow:established,to_server; content:"head "; depth:5; nocase; content:!"HEAD "; depth:5; reference:url,www.w3.org/Protocols/rfc2616/rfc2616-sec9.html; classtype:bad-unknown; sid:2011033; rev:4; metadata:created_at 2010_07_30, confidence Medium, signature_severity Informational, updated_at 2019_07_26;)