alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Possible APT28 Maldoc CnC Checkin"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/software-protection/app.php"; startswith; fast_pattern; endswith; http.connection; content:"Keep-Alive"; http.header_names; content:!"Referer"; content:!"Accept"; content:!"Cache"; reference:url,blog.telsy.com/zebrocy-dropbox-remote-injection/; classtype:targeted-activity; sid:2027939; rev:3; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, created_at 2019_09_02, deployment Perimeter, performance_impact Low, confidence Medium, signature_severity Major, tag APT28, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_17;)