alert http any any -> [$HOME_NET,$HTTP_SERVERS] any (msg:"ET EXPLOIT Possible Microsoft Exchange RCE Inbound M2 (CVE-2021-34473)"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/autodiscover.json?"; content:"/PowerShell/"; nocase; distance:0; content:"X-Rps-CAT="; distance:0; fast_pattern; content:"Email="; distance:0; content:"autodiscover/"; within:20; reference:cve,2021-34473; classtype:attempted-admin; sid:2033711; rev:3; metadata:affected_product Microsoft_Exchange, attack_target Server, created_at 2021_08_12, cve CVE_2021_34473, deployment Perimeter, deployment Internal, deployment SSLDecrypt, confidence Medium, signature_severity Major, tag Exploit, tag CISA_KEV, updated_at 2024_03_08, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;)