alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET INFO DNS Over HTTP Style Request (GET)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/d?dn="; fast_pattern; startswith; http.host; pcre:"/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/"; http.header_names; content:!"Referer"; reference:md5,8feb11d15b708736189779ddc51a4a0a; classtype:misc-activity; sid:2048360; rev:1; metadata:attack_target Client_Endpoint, created_at 2023_09_29, deployment Perimeter, performance_impact Low, confidence Medium, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_09_29, reviewed_at 2023_09_29; target:src_ip;)