alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET INFO Certificate with Unknown Content M1"; flow:established,to_client; file.data; content:"-----BEGIN CERTIFICATE-----|0D 0A|"; startswith; fast_pattern; byte_test:1,!=,0x4D,0,relative; reference:url,blog.nviso.be/2018/07/31/powershell-inside-a-certificate-part-1/; classtype:misc-activity; sid:2026649; rev:4; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2018_11_26, deployment Perimeter, performance_impact Moderate, confidence Medium, signature_severity Major, updated_at 2024_04_14;)