Maybe you could also display that information when you show a captcha. "We've observed x login attempts from your IP in the last y days." Usually you wouldn't

Maybe you could also display that information when you show a captcha. "We've observed x login attempts from your IP in the last y days." Usually you wouldn't want to make it easy for botnet owners to find out they've been caught, but since displaying the captcha already reveals that, having an explanation might help regular users who got a low-reputation IP assigned.