alert ftp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/WhiskerSpy - FTP STOR Command M2"; flow:established,to_server; content:"STOR h"; pcre:"/^[a-f0-9]{16}\x0d\x0a/R"; reference:md5,cdf9e79b37ae70fb19b504f81e655d2a; reference:url,trendmicro.com/en_us/research/23/b/earth-kitsune-delivers-new-whiskerspy-backdoor.html; classtype:command-and-control; sid:2044256; rev:1; metadata:attack_target Client_and_Server, created_at 2023_02_20, deployment Perimeter, malware_family WhiskerSpy, performance_impact Moderate, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_02_20; target:src_ip;)