alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Sidewalk CnC Checkin"; flow:established,to_server; http.method; content:"POST"; http.header_names; content:"|0d 0a|gtuvid|0d 0a|"; fast_pattern; content:"|0d 0a|gtsid|0d 0a|"; reference:url,welivesecurity.com/2021/08/24/sidewalk-may-be-as-dangerous-as-crosswalk/; classtype:command-and-control; sid:2033937; rev:3; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_09_13, deployment Perimeter, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_07_17;)