Progressive challenge in @doublegram_captcha_bot (challenge escalation) adapts reCAPTCHA difficulty to each Telegram joiner's suspicion score. Legitimate users with complete profiles often verify without clicking anything.
Suspicion score factors
| Factor | Effect |
|---|---|
| No Telegram username | +1 suspicion |
| No profile photo | +1 suspicion |
| Telegram Premium | −1 suspicion |
| Previous failed verifications | +1 suspicion |
On join, @doublegram_captcha_bot checks username, calls Telegram for profile photos, reads Premium status, and stores flags on the verification token.
Challenge levels
| Score | reCAPTCHA type | User experience |
|---|---|---|
| 0–1 | Invisible | Automatic background check, no checkbox |
| 2+ | Checkbox | User must click "I'm not a robot" |
Why this helps
- Bot and raid accounts often lack photos and usernames
- Real users with established profiles verify faster
- Repeat offenders who failed captcha before face stricter checks
Not configurable: Suspicion rules are automatic — admins cannot tune score weights in /settings. Adjust trust and firewall for policy control.
Quick reference
- Low risk: invisible reCAPTCHA
- High risk: checkbox reCAPTCHA
- Signals: username, photo, Premium, history
- Automatic: no admin toggle
Related: force verification on an existing member with /captcha — see Force Verification with /captcha on Telegram.