alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE IrcBot Downloading .old"; flow:established,to_server; http.start; content:".old|20|HTTP/1.1|0d 0a|Host"; fast_pattern; http.header_names; content:!"User-Agent"; content:!"Referer"; content:!"Accept"; reference:md5,ca6208a4dd3f1f846aaaf4a6cbcc66ea; classtype:trojan-activity; sid:2022657; rev:4; metadata:created_at 2016_03_24, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_11_05;)