alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE W32.Nemim Checkin"; flow:to_server,established; http.uri; content:".php?a1="; nocase; fast_pattern; content:"&a2="; nocase; content:"&a3="; nocase; pcre:"/\.php\?a1=(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})&a2=[a-f0-9]{32}&a3=(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/i"; reference:url,symantec.com/connect/blogs/infostealernemim-how-pervasive-infostealer-continues-evolve; classtype:command-and-control; sid:2017599; rev:6; metadata:created_at 2013_10_15, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_05;)