Spam comment a lot, how to solve?

As the title question, here my problem is the items can be comment without many restrict (Attach pic below).

So that a few people jz put many spam info in my website.
To better to solve this problem I think it is a good choice to only let register user comment.

Is there any way can achieve that?

(Means anonymous users cannot comment, there will be "Please login to leave comment", and comment form will hide.
The registered user can comment as normal.)

Please give any idea to solve?

Hello dongeyoung,

You can change the parameter called "Global setting for comments" in K2 Parameters > Comment

Please see the picture for more details. Good Luck