Rule History

alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET HUNTING Observed Let's Encrypt Certificate for Suspicious TLD (.icu)"; flow:established,to_client; tls.cert_subject; content:".icu"; endswith; tls.cert_issuer; content:"Let's Encrypt"; classtype:bad-unknown; sid:2026890; rev:3; metadata:attack_target Client_Endpoint, created_at 2019_02_06, deployment Perimeter, confidence Medium, signature_severity Minor, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_09_16;)