Possible hack attempts - how to thwart

I just did a tail of my log file in apache and am getting non-stop action on my wordpress multi-site. I've uploaded a youtube video of the tail here: http://youtu.be/2_ia3rk-o9c

It seems to me someone is trying to brute force an admin login or to insert an admin login but I'm open to thoughts from the group. I need someone who can look at that code and know what's happening.

Of course then there's the other 1/2, how to prevent this as it's eating up server resources.

What sayeth the group ?

Jay Lepore