Someone made a CAPTCHA where you play Doom on Nightmare difficulty - Ars Technica
- Someone made a CAPTCHA where you play Doom on Nightmare difficulty Ars Technica
- Protect Your Site With A DOOM Captcha Hackaday
- New Captcha requires defeating three enemies or you're Doomed to repeat it Tom's Hardware
- Prove you're human by playing Doom in a captcha Boing Boing
- People are playing a new DOOM-themed CAPTCHA TechCrunch