alert http $EXTERNAL_NET any -> $HTTP_SERVERS any (msg:"ET SCAN SQLNinja MSSQL User Scan"; content:"?param=a"; flow:to_server,established; content:"if%20ascii%28substring%28%28select%20system%5Fuser"; distance:2; threshold:type threshold, track by_src, count 20, seconds 10; reference:url,sqlninja.sourceforge.net/index.html; classtype:attempted-recon; sid:2009040; rev:5; metadata:created_at 2010_07_30, confidence Medium, signature_severity Informational, updated_at 2019_09_27;)