alert tcp $EXTERNAL_NET any -> $SMTP_SERVERS 25 (msg:"ET POLICY SMTP Executable attachment"; flow:established,to_server; content:"filename="; nocase; content:".exe"; nocase; distance:0; pcre:"/filename=\s*[^\n]+\.exe/i"; classtype:policy-violation; sid:2003325; rev:4; metadata:created_at 2010_07_30, confidence High, signature_severity Informational, updated_at 2019_07_26;)