I've had this WP site up for a couple years, and recently it started asking me the following "captcha" every time I visit the login screen:
WordPress administrator CAPTCHA. Enter username: eaasvm Password: The result of math 28+4
It seems very fishy, I don't think it's supposed to be there. It appears as an authentication popup, something that would be created by a .htaccess file. I've searched through all the .htaccess files on my server, and I haven't found anything.
See this link for screenshot: http://imgur.com/91gQfW8