alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET EXPLOIT_KIT CoolEK Payload Download (9)"; flow:established,to_server; http.uri; content:".txt?f="; fast_pattern; pcre:"/^\d+$/R"; http.header_names; content:!"Referer|0d 0a|"; classtype:exploit-kit; sid:2016976; rev:12; metadata:created_at 2013_06_06, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_28;)