alert tcp $HOME_NET any -> $EXTERNAL_NET 80 (msg:"ET MALWARE QDIGIT Trojan Protocol detected"; flow:to_server,established; content:"|51 31 39 21 00|"; depth:5; dsize:5; reference:url,www.commandfive.com/papers/C5_APT_C2InTheFifthDomain.pdf; classtype:trojan-activity; sid:2014222; rev:2; metadata:created_at 2012_02_14, signature_severity Major, updated_at 2019_07_26;)