Strange problem logging in to the ftp server

Hi,

when I try to log in in the same lan to the ftp server I have no problem but I get a line in /var/log/massages:
Nov 12 23:55:28 attackbox vsftpd(pam_uni:evil:[3353]: check pass; user unknown
Nov 12 23:55:28 attackbox vsftpd(pam_uni:evil:[3353]: authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=192.168.1.11

but there is no problem to log in
when I try to log in from the internet I see this error:

Nov 12 23:51:50 attackbox pam_tally[3245]: pam_tally: pam_get_uid; no such user anonymous
Nov 12 23:51:50 attackbox vsftpd(pam_uni:evil:[3245]: check pass; user unknown
Nov 12 23:51:50 attackbox vsftpd(pam_uni:evil:[3245]: authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=89.138.242.223

in /etc/password this is what I have for the user who I always use for ftp:
juan:x:511:502::/home/tests:/bin/bash

Does someone knows whats the problem and why I cant log in from the internet?

Thanks !!

Juan