alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/SystemBC CnC Checkin (null key) M1"; flow:established,to_server; dsize:100; content:"|00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00|"; startswith; content:"|89 40|"; distance:2; within:2; content:"|46 ad 57 90|"; fast_pattern; endswith; reference:md5,b8fb4ba9ef16fcaa442c2857bb045640; classtype:command-and-control; sid:2033004; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_05_20, deployment Perimeter, malware_family SystemBC, performance_impact Moderate, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_05_20;)