alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET WEB_CLIENT Tech Support Scam Landing 2018-07-18"; flow:established,to_client; http.stat_code; content:"401"; http.header; content:"WWW-Authenticate|3a 20|Basic realm=|22|Microsoft has detected suspicious activity"; fast_pattern; classtype:social-engineering; sid:2025831; rev:3; metadata:affected_product Web_Browsers, attack_target Client_Endpoint, created_at 2018_07_18, deployment Perimeter, confidence High, signature_severity Major, tag Tech_Support_Scam, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_01;)