alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE ProxyBox - HTTP CnC - POST 1-letter.php"; flow:established,to_server; urilen:6; http.method; content:"POST"; http.uri; content:".php"; pcre:"/^\/[a-z]\.php/"; http.user_agent; content:"Indy Library"; reference:url,www.symantec.com/security_response/writeup.jsp?docid=2012-071005-4515-99&tabid=2; classtype:command-and-control; sid:2015504; rev:6; metadata:created_at 2012_07_21, signature_severity Major, updated_at 2020_10_28;)