alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET POLICY Observed External IP Lookup SSL Cert"; flow:from_server,established; tls.cert_subject; content:".iplocation.com"; nocase; fast_pattern; tls.cert_issuer; content:"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3"; classtype:external-ip-check; sid:2026882; rev:4; metadata:attack_target Client_Endpoint, created_at 2019_02_05, deployment Perimeter, performance_impact Low, confidence High, signature_severity Informational, tag IP_address_lookup_website, updated_at 2024_09_19, mitre_tactic_id TA0007, mitre_tactic_name Discovery, mitre_technique_id T1614, mitre_technique_name System_Location_Discovery;)