I have updated ispconfig to 3.0.5.2, it auto block customers ip. I run #iptables-save|grep 61.240.36.94 It show -A DENYIN -s 61.240.36.94/32 ! -i lo -j DROP -A DENYOUT -d 61.240.36.94/32 ! -o lo -j DROP What happen?
A user with that IP entered a password several times wrong e.g. for pop3, imap or ftp and was blocked for a few minutes. This is done to protect your server against brute force password attacks.