alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET HUNTING Possible COVID-19 Domain in SSL Certificate M2"; flow:established,to_client; tls.cert_subject; content:"covid"; nocase; content:!".jhu.edu"; isdataat:!1,relative; content:!".ncsc.gov.ie"; isdataat:!1,relative; content:!".nhs.wales"; isdataat:!1,relative; content:!".govt.nz"; isdataat:!1,relative; content:!".nhp.gov.in"; isdataat:!1,relative; content:!".oracle.com"; isdataat:!1,relative; content:!".cdc.gov"; isdataat:!1,relative; content:!".canada.ca"; isdataat:!1,relative; content:!"CN=*.nicovideo.jp"; classtype:bad-unknown; sid:2029706; rev:5; metadata:affected_product Web_Browsers, attack_target Client_Endpoint, created_at 2020_03_23, deployment Perimeter, confidence Medium, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_08_02;)