alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Observed ProtonBot User-Agent"; flow:established,to_server; http.user_agent; content:"Proton Browser"; fast_pattern; http.header_names; content:!"Referer"; reference:url,fumik0.com/2019/05/24/overview-of-proton-bot-another-loader-in-the-wild; reference:md5,efb1db340e78f6799d9fbc5ee08f40fe; classtype:trojan-activity; sid:2027384; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2019_05_28, deployment Perimeter, malware_family ProtonBot, performance_impact Moderate, confidence High, signature_severity Major, updated_at 2020_08_31;)