alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"ET HUNTING Telegram API Certificate Observed"; flow:established,to_client; tls.cert_subject; content:"CN=api.telegram.org"; fast_pattern; nocase; endswith; classtype:misc-activity; sid:2029322; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2020_01_27, deployment Perimeter, confidence High, signature_severity Minor, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_27;)