alert http $HOME_NET any -> $EXTERNAL_NET any (
msg:"ET MALWARE ShadowLink IoT Botnet CnC Checkin Attempt M2";
flow:established,to_server;
http.method;
content:"POST";
http.uri; bsize:5;
content:"/b/in";
http.header;
content:"X-B|3a 20|"; fast_pattern;
http.request_body;
content:"|22|h|22|";
content:"|22|u|22|";
content:"|22|o|22|";
reference:url,ctrlaltintel.com/research/ProxyPCP/;
classtype:trojan-activity;
sid:2068791; rev:1;
metadata:affected_product IoT, attack_target Networking_Equipment, tls_state TLSDecrypt, created_at 2026_04_15, deployment Perimeter, deployment SSLDecrypt, malware_family ShadowLink, performance_impact Low, confidence High, signature_severity Major, updated_at 2026_04_15;
target:src_ip;
)