alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Linux/ChinaZ DDoS Bot Checkin"; flow:established,to_server; content:"|00 00 00 00|"; depth:4; content:!"|00|"; within:1; content:"MHz|00|"; distance:0; content:"|20 2a 20|"; distance:-12; within:5; pcre:"/^\d+MHz\x00/R"; content:"|20|MB|00|"; distance:0; fast_pattern; reference:url,kernelmode.info/forum/viewtopic.php?f=16&t=3682; classtype:command-and-control; sid:2020188; rev:1; metadata:created_at 2015_01_15, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)