alert http $EXTERNAL_NET any -> $HTTP_SERVERS any (msg:"GPL WEB_SERVER perl command attempt"; flow:to_server,established; http.uri; content:"/perl?"; nocase; reference:arachnids,219; reference:cve,1999-0509; reference:nessus,10173; reference:url,www.cert.org/advisories/CA-1996-11.html; classtype:attempted-recon; sid:2101649; rev:11; metadata:created_at 2010_09_23, cve CVE_1999_0509, signature_severity Unknown, updated_at 2020_04_20;)