alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET RETIRED Possible Bot CnC Checkin (GET)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"?register=V2luZG93"; fast_pattern; http.header_names; to_lowercase; content:!"|0d 0a|referer|0d 0a|"; reference:md5,d4fdd80e3f4b1ef0e6c3904d91e5d319; classtype:bad-unknown; sid:2036381; rev:4; metadata:attack_target Client_Endpoint, created_at 2022_04_26, deployment Perimeter, former_category HUNTING, performance_impact Low, confidence Medium, signature_severity Major, updated_at 2024_09_12, reviewed_at 2024_09_12;)