alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Backoff Variant Checkin"; flow:established,to_server; http.method; content:"GET"; http.uri; content:".php?a=start&id="; fast_pattern; pcre:"/&id=[A-F0-9]+$/"; http.header_names; content:!"Referer|0d 0a|"; reference:md5,d8e7983004c5545df6de868bc0c5a947; classtype:command-and-control; sid:2019636; rev:4; metadata:created_at 2014_11_04, signature_severity Major, updated_at 2020_09_25;)