alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/Coreshell Checkin (APT28 Related)"; flow:to_server,established; http.method; content:"POST"; http.uri; content:"/~xh/sn.cgi?"; fast_pattern; pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})+?$/R"; reference:url,www.fireeye.com/resources/pdfs/apt28.pdf; reference:md5,272f0fde35dbdfccbca1e33373b3570d; classtype:targeted-activity; sid:2019539; rev:5; metadata:created_at 2014_10_28, malware_family Win32_Coreshell, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_05_13;)