alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE [PTsecurity] Botnet Nitol.B Checkin"; flow:established,to_server,no_stream; dsize:<400; content:"|00 00 77 00 00 00|"; depth:30; fast_pattern; content:"MHz"; within:350; content:"|00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00|"; depth:120; classtype:command-and-control; sid:2025135; rev:4; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2017_12_06, deployment Perimeter, malware_family nitol, performance_impact Moderate, confidence High, signature_severity Minor, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_08_19;)