alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Knockbot Proxy Response From Controller"; flow:established,from_server; content:"|0d 0a 0d 0a|command|7c|file|7c|http"; depth:250; nocase; content:"|7c|"; within:150; reference:url,www.malwaredomainlist.com/mdl.php?search=knock.php; classtype:trojan-activity; sid:2010787; rev:5; metadata:created_at 2010_07_30, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)