New POP3 vulnerability?

[Neil Joseph Schelly]

I'm wondering if anyone knows of any new POP3 vulnerability out there?  Twice 
in the last few days, I've seen password guessing attacks on my POP3 server, 
akin to the obviously common SSH password guessing stuff (using usernames 
like root, admin, etc).  I was wondering if anyone else has noticed this 
behavior and/or what has caused this recent uptake.  Or maybe the problem is 
just mine?
-N