alert http any any -> [$HOME_NET,$HTTP_SERVERS] any (msg:"ET EXPLOIT Microsoft Exchange Pre-Auth Path Confusion M1 (CVE-2021-31207)"; flow:established,to_server; http.uri; content:"/autodiscover"; nocase; fast_pattern; content:"Email=autodiscover/"; nocase; flowbits:set,ET.cve.2021.34473; reference:cve,2021-31207; classtype:attempted-admin; sid:2033681; rev:4; metadata:affected_product Microsoft_Exchange, attack_target Server, created_at 2021_08_09, cve CVE_2021_31207, deployment Perimeter, deployment Internal, deployment SSLDecrypt, confidence High, signature_severity Major, tag Exploit, tag CISA_KEV, updated_at 2022_12_23, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;)