alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET WEB_CLIENT Tech Support Phone Scam Landing M1 Oct 16 2016"; flow:from_server,established; http.stat_code; content:"401"; http.header; content:"WWW-Authenticate|3a 20|Basic realm="; nocase; content:"Error"; nocase; distance:0; fast_pattern; content:"-"; distance:0; pcre:"/^WWW-Authenticate\x3a\x20Basic\x20realm=[\x22\x27][^\r\n]*Error[^\r\n]*-/mi"; classtype:social-engineering; sid:2024844; rev:5; metadata:created_at 2017_10_16, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_01;)