alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET HUNTING URL Observed in PDF Downloaded via Dropbox"; flow:established,to_client; http.stat_code; content:"200"; http.header; content:"x-dropbox-request-id|3a|"; file.data; content:"|25 50 44 46|"; depth:4; content:"/Type /Action /S /URI"; fast_pattern; nocase; classtype:misc-activity; sid:2030047; rev:2; metadata:affected_product Web_Browsers, attack_target Client_Endpoint, created_at 2020_04_28, deployment SSLDecrypt, confidence Medium, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_04_28;)