alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET INFO Psiphon VPN Related Activity (POST)"; flow:established,to_server; http.method; content:"POST"; http.uri; bsize:1; content:"/"; http.header_names; to_lowercase; content:"|0d 0a|content-length|0d 0a|content-type|0d 0a|cookie|0d 0a|accept-encoding|0d 0a 0d 0a|"; fast_pattern; content:!"|0d 0a|referer|0d 0a|"; http.content_type; bsize:24; content:"application/octet-stream"; http.cookie; pcre:"/^[A-Z]=[A-Za-z/+0-9=]{200,400}$/"; reference:md5,912e361d280d881980caca25cd0b80d4; classtype:bad-unknown; sid:2037033; rev:3; metadata:attack_target Client_Endpoint, created_at 2022_06_17, deployment Perimeter, performance_impact Moderate, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_04_30;)