How does Stack Overflow handle spam?
2 Answers
new user limits (only 1 url allowed in posts, only 1 question per 20 minutes, only 1 answer per 3 minutes)
captcha
script detection heuristics and "honeypots"
user flagging (spam / offensive / moderator attention)
auto-removal of some items based on certain flag thresholds being met
active moderator participation throughout the day to look at moderator flagged items
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1So why do established accounts still get the captcha occasionally?– Perpetual Motion GoatJul 6, 2009 at 14:18
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"Established accounts" could be picked-up and used by scripts after human-establishment.– SampsonJul 6, 2009 at 14:26
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What are these "honeypots" that you speak of (in the context of SO, not in general)?– AnandJul 6, 2009 at 15:00
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auto-removal of some items based on certain flag thresholds being met - does this mean Spam-Assassin-style Bayesian filtering? May 7, 2010 at 13:39
They use reCAPTCHA to ask for CAPTCHA's if there are frequent actions performed (although this is more a preventative measure than for actually dealing with it).
There are also the moderators in place, who can delete posts that are deemed as spam, and the community, who are the ones who flag posts as spam to get the moderators' attention.