After loosing my eye on this site for some time, I found my site (again, surprisingly) flooded with heaps of search query that contains porn links.

The bot just keep sending queries via the search function on my weblog...
I mean, I've spent a lot of time on writing codes to prevent and to block spam content on my site. For example having user to input image verification code, filtering offensive words & blacklisting domains name before user can post any shout, comments or even pm me. But there are always something spammers/bots can do to surprise you.
The IP
84.16.240.251 belongs to GERMANY and it's now banned. The IP is static and didn't change in a month -_-