alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE S400 RAT Client Checkin"; flow:established,to_server; stream_size:server,<,5; dsize:5; content:"|33 00|FCC"; fast_pattern; reference:md5,41ca8d5782ef5ac7a371b44f51dc48d9; classtype:command-and-control; sid:2034063; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_09_30, deployment Perimeter, malware_family S400, confidence High, signature_severity Major, tag RAT, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_09_30;)