alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Suspicious Fake Opera 10 User-Agent"; flow:established,to_server; http.user_agent; content:"Opera/10|20|"; fast_pattern; http.header_names; content:!"Accept|0d 0a|"; reference:url,dev.opera.com/articles/view/opera-ua-string-changes; reference:url,blog.avast.com/2013/05/03/regents-of-louisiana-spreading-sirefef-malware; classtype:trojan-activity; sid:2016823; rev:6; metadata:created_at 2013_05_04, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_18;)