alert http $EXTERNAL_NET any -> $HTTP_SERVERS any (msg:"ET SCAN Grendel Web Scan - Default User Agent Detected"; flow:to_server,established; threshold:type limit, track by_dst, count 1, seconds 60; http.header; content:"http|3a|//www.grendel-scan.com"; nocase; http.user_agent; content:"Mozilla/5.0 (compatible|3b 20|Grendel-Scan"; nocase; depth:37; fast_pattern; reference:url,www.grendel-scan.com; classtype:attempted-recon; sid:2009480; rev:10; metadata:created_at 2010_07_30, confidence High, signature_severity Informational, updated_at 2020_10_14;)