alert tcp $SMTP_SERVERS any -> $EXTERNAL_NET 25 (msg:"ET DELETED SMTP US Top Secret ORCON"; flow:to_server,established; content:"Subject|3A|"; pcre:"/(TOP\sSECRET|TS)//[\s\w,/-]*(ORIGINATOR\sCONTROLLED|ORCON)[\s\w,/-]*(?=//(25)?X[1-9])/ism"; classtype:policy-violation; sid:2002444; rev:4; metadata:created_at 2010_07_30, signature_severity Unknown, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)