Login Spam

Lately, I have been getting a lot of obvious bots signing up. Their usernames are random alpha-characters, and their email addresses, so far, have been [whatever]@[domain].info. Here’s the latest, extra space removed:

———————————————
New user registration on your blog [my blog]:
Username: frkksptn
E-mail: fkfxbsdpw@obdolbin.info
———————————————

I’ve been deleting them on a case-by-case basis, but the rate of registrations is increasing. Are there any plans to add image verification (or something) to the registration process?