alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE W32/InstallMonster.Downloader Checkin"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/api"; http.user_agent; content:"Mozilla/3.0|20|(compatible|3b 20|Indy Library)"; endswith; fast_pattern; http.protocol; content:"HTTP/1.0"; http.header_names; content:!"Referer"; content:!"Content-Type"; reference:md5,70a6d9cb37e346b4dfd28bd4ea1f8671; classtype:command-and-control; sid:2017656; rev:6; metadata:created_at 2013_11_01, signature_severity Major, updated_at 2020_08_17;)