Log all login failures

[sebz2009]

Out forums are being accessed by roughly 10 Tor exit nodes each day, and we know who it is that's doing it. (Each time I find one though, I block him from allowing access on the site via a .htaccess file)
I'm just wondering if it's possible to log all failed login attempts into a file with the username and password they tried, the time of it and what IP.

I know it's possible to do it for the admin login (which I've set up), I just want to have it so we can see what the hacker's thinking and hopefully stop him.