alert http1 $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Possible Sinkhole banner"; flow:established,to_client; http.server; content:"You got served|21|"; startswith; reference:url,community.emc.com/community/connect/rsaxchange/netwitness/blog/2013/12/30/detecting-sinkholed-domains-in-your-environment; classtype:trojan-activity; sid:2018117; rev:7; metadata:created_at 2014_02_12, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_04_18;)