alert tcp $EXTERNAL_NET any -> $HOME_NET 21 (msg:"GPL FTP RETR format string attempt"; flow:to_server,established; content:"RETR"; nocase; pcre:"/^RETR\s[^\n]*?%[^\n]*?%/smi"; reference:bugtraq,9800; classtype:attempted-admin; sid:2102574; rev:2; metadata:created_at 2010_09_23, signature_severity Unknown, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)