alert http $HOME_NET any -> $EXTERNAL_NET any (
msg:"ET MALWARE Win32/Voltron/Spectre Stealer Checkin Activity (GET)";
flow:established,to_server;
http.method;
content:"GET";
http.uri;
content:"/v4/api_t.php?id="; startswith; fast_pattern;
http.user_agent;
content:"UserAgent"; bsize:9;
http.header_names;
content:!"Referer";
classtype:trojan-activity;
sid:2034038; rev:1;
metadata:attack_target Client_Endpoint, created_at 2021_09_17, deployment Perimeter, malware_family Win32_Voltron_Spectre, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_09_17;
)