alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE SSL/TLS Certificate Observed (WRAT)"; flow:established,to_client; tls.cert_subject; content:"CN=alsalaf.info"; fast_pattern; tls.cert_issuer; content:"C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3"; reference:md5,7831f12dac1d4ef7dcd6e3218b8dad68; classtype:trojan-activity; sid:2031645; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_02_22, deployment Perimeter, confidence High, signature_severity Major, tag WRAT, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_02_22;)