alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Connectivity Check of Unknown Origin 3"; flow:established,to_server; urilen:16; http.method; content:"GET"; http.uri; content:"/images/logo.gif"; http.user_agent; bsize:24; content:"Mozilla/4.0 (compatible)"; http.host; bsize:21; content:"www.study-centers.com"; fast_pattern; http.header; content:"Cache-Control|3a 20|no-cache|0d 0a|"; http.header_names; content:"|0d 0a|User-Agent|0d 0a|Host|0d 0a|Cache-Control|0d 0a|"; startswith; classtype:trojan-activity; sid:2013351; rev:5; metadata:created_at 2011_08_04, confidence Medium, signature_severity Major, updated_at 2024_03_05;)