Multi-accounting is the #1 abuse vector for SaaS platforms, marketplaces, and gaming sites. One person creates dozens or hundreds of accounts to exploit free trials, promotions, referral programs, or voting systems.

Why It's Hard to Stop

Traditional approaches fail because fraudsters have evolved:

  • Email aliases: Gmail's dot trick (j.ohn vs john) and + aliases create unlimited email addresses
  • Residential proxies: Each account appears to come from a different home IP — clean, no flags
  • Antidetect browsers: Tools like Kameleo and GoLogin create unique device fingerprints for each account
  • VPNs: Cheap VPN subscriptions provide thousands of IP addresses

IP blocking doesn't work (residential proxies). Email verification doesn't work (unlimited aliases). CAPTCHAs don't work (AI solvers). Even device fingerprinting alone doesn't work (antidetect browsers spoof it).

What Actually Works

The solution is layered detection — combining multiple signals that are hard to fake simultaneously:

  • Device fingerprinting + tampering detection: Detect if the browser fingerprint is spoofed (antidetect browsers leave detectable traces even when spoofing)
  • Network intelligence: Flag VPNs, proxies, and residential proxy networks
  • Behavioral analysis: Detect patterns across accounts (same typing speed, same navigation patterns)
  • Visitor identification: Persistent device IDs that survive cookie clearing and incognito mode

Implementation with Sentinel

Sentinel combines all four layers in a single API call. When a user signs up:

  1. The Sentinel SDK collects a security token (invisible to the user)
  2. Your backend sends the token to POST /v1/evaluate
  3. Sentinel returns whether the connection is suspicious + a persistent visitor ID
  4. You check if that visitor ID has already created an account

If isSuspicious: true or the visitor ID matches an existing account → block the signup. No CAPTCHA, no friction for real users.

Results

Platforms using this approach typically see 90-97% reduction in multi-accounting within the first week. The key is that antidetect browsers can spoof individual fingerprint signals, but they can't spoof the tampering indicators that Sentinel detects.

Try it free at sntlhq.com — 1,000 requests/hour, no credit card required.