alert http $HTTP_SERVERS $HTTP_PORTS -> $EXTERNAL_NET any (msg:"ET ATTACK_RESPONSE HTTP 401 Unauthorized"; flow:from_server,established; content:"401"; http_stat_code; threshold:type both, count 1, seconds 300, track by_dst; classtype:attempted-recon; sid:2009345; rev:8; metadata:created_at 2010_07_30, signature_severity Unknown, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)