[andy]

Zależy od konfiguracji. Może pisze do /var/log/syslog?

Unix syslog Logging
By default, proftpd will log via syslog(3), using the daemon facility (auth for some logging), at various levels: err, notice, warn, info, and debug (debugging is done at this syslog level). The location of the server's log files in this case is determined by your /etc/syslog.conf configuration.

Co mówi man proFTPd?

U siebie mam vsftpd