alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Dridex Dotted Quad CnC Request (flowbit set)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/"; startswith; pcre:"/^[A-Z0-9]{15,40}$/R"; http.host; pcre:"/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}(?:\x3a\d+)?$/"; flowbits:set,ET.Dridex.Email.Sets.1; flowbits:noalert; classtype:command-and-control; sid:2034533; rev:2; metadata:created_at 2021_11_23, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_11_24;)