alert tcp $EXTERNAL_NET any -> $HOME_NET 110 (msg:"GPL POP3 APOP USER overflow attempt"; flow:to_server,established; content:"APOP"; nocase; isdataat:256,relative; pcre:"/^APOP\s+USER\s[^\n]{256}/smi"; reference:bugtraq,9794; classtype:attempted-admin; sid:2102409; rev:2; metadata:created_at 2010_09_23, confidence Medium, signature_severity Major, updated_at 2019_07_26;)