how is 4ch spam protected?

short question: how do you protect your board from automated bot spamming? i cant see any captcha! normally, from my expirience, a board  would  be instantly spammed to death without captcha or such protective measures. but 4ch board seems to be free of those problems... how do you do that ?

>>24
Proxy checker and a list of known proxy IPs. I don't live to moderate my board either; I just have other measures in place. (And, another simple check -- which most boards already have -- is a post delay, which also helps to slow posting down. All the captcha is doing if you have a post throttling mechanism is keeping the flooders busy while their time window resets.)

I'm not saying that the average spammer is *going* to circumvent captchas. All I'm suggesting is, why go to the trouble of implementing a captcha system when tossing a dummy field and two if statements in the code will accomplish essentially the same effect?