alert tcp $EXTERNAL_NET any -> $SMTP_SERVERS 25 (msg:"ET MALWARE Post Express Inbound bad attachment"; flow:established,to_server; content:"Post Express|22|"; nocase; content:"Content-Disposition|3a| attachment|3b|"; nocase; content:"filename=|22|Post_Express_"; nocase; content:".zip|22|"; nocase; classtype:trojan-activity; sid:2012445; rev:6; metadata:created_at 2011_03_09, signature_severity Major, updated_at 2019_07_26;)