alert tcp-pkt $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE FSB Snake CnC Activity Inbound via TCP (AA23-129A) M3"; flow:established,to_client; content:"|00 00 00 04|"; startswith; dsize:4; flowbits:isset,snake-b8; flowbits:unset,snake-b8; flowbits:set,snake-b41; flowbits:noalert; reference:url,cisa.gov/news-events/cybersecurity-advisories/aa23-129a; classtype:command-and-control; sid:2045642; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2023_05_11, deployment Perimeter, malware_family Snake, performance_impact Moderate, confidence Medium, signature_severity Major, tag AA23_129A, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_05_11;)