alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Trojan.Bayrob Keepalive"; flow:established,to_server; urilen:9; http.method; content:"GET"; http.uri; content:"/isup.php"; fast_pattern; http.header.raw; content:"Accept-Encoding|3a 20 20 20 20 20 20 20 20 20 20 20 20 20|"; http.header_names; content:!"Referer|0d 0a|"; reference:md5,a4a3fab712b04ee901f491d4c704b138; classtype:trojan-activity; sid:2020621; rev:7; metadata:created_at 2015_03_05, deprecation_reason Age, confidence High, signature_severity Major, updated_at 2024_03_26, reviewed_at 2024_03_26;)