alert tcp $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE ELF/Emptiness v1.1 HTTP Flood Command Inbound"; flow:established,from_server; dsize:<50; content:"Lmh0dHA"; depth:7; fast_pattern; pcre:"/^(?:[A-Z0-9+/]{4})*(?:[A-Z0-9+/]{2}==|[A-Z0-9+/]{3}=|[A-Z0-9+/]{4})$/i"; reference:url,blog.netlab.360.com/emptiness-a-new-evolving-botnet/; classtype:trojan-activity; sid:2027842; rev:2; metadata:affected_product Linux, created_at 2019_08_09, malware_family Emptiness, confidence High, signature_severity Major, tag DDoS, updated_at 2019_10_23;)