alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET WEB_CLIENT Tech Support Phone Scam Landing M1 Oct 16 2016"; flow:established,to_client; http.stat_code; content:"401"; http.response_header; header_lowercase; content:"www-authenticate|3a 20|Basic|20|realm|3d|"; startswith; nocase; content:"Error"; nocase; distance:0; fast_pattern; content:"-"; distance:0; classtype:social-engineering; sid:2024844; rev:7; metadata:created_at 2017_10_16, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_04_28;)