The hidden cost of bad sign-ups (and how to stop them)

Every product team wants more users signing up, but not all sign-ups are created equal.

If you’re letting disposable emails, bots, and repeat free trial sign-ups slip through the cracks, your growth numbers may look healthy on paper while hiding costly problems underneath. Fake accounts skew analytics, waste engineering resources, create compliance risks, and can even erode trust with your real users.

Not every new user is a good user. Disposable emails, bots, and repeat free trial sign-ups may boost your top-line growth numbers, but they quietly chip away at your business. Fake accounts inflate KPIs, pollute your analytics, waste engineering effort, and even create compliance risk. Left unchecked, they can undermine trust in your data and damage your bottom line.

The reality is simple: when you can’t trust the quality of your sign-ups, you can’t trust the growth story they’re telling. We built a product that offers a layered defense at sign-up, blocking disposable emails, bots, and repeat abuse before they reach your funnel.

The hidden cost of low-quality sign-ups

Disposable email addresses and automated sign-ups may seem harmless at first. After all, more accounts = more growth, right? But here’s what really happens:

• Abuse of free trials and free tiers: Disposable emails let bad actors spin up endless accounts to avoid paying.
• Inflated metrics: Fake sign-ups distort conversion rates and active user counts, making it harder to judge product-market fit.
• Compliance headaches: Accounts from sanctioned regions or fraudulent identities can expose you to regulatory risk.
• Operational drag: Engineering and support teams waste time handling abuse rather than building the product.

When “sign-up growth” comes at the cost of accuracy and trust, it’s not growth at all.

Why DIY doesn’t scale

Some teams try to fight this with hand-rolled solutions: blocking known domains with regex filters, adding CAPTCHAs, or cleaning user data after the fact.

But attackers adapt quickly:

• Disposable email domains: Thousands of new ones appear each month. Unless your blocklist updates continuously, it’s obsolete.
• Bots: Off-the-shelf tools simulate real browsers, bypassing simple form protections.
• Repeat sign-ups: Even with email verification, abusers rotate through addresses and IPs.
• Compliance: Regulations like OFAC lists change, and monitoring them manually is brittle.

DIY solutions often lag attackers by weeks or months. By then, your sign-up data is already polluted.

A layered defense with WorkOS Radar

Stopping bad sign-ups isn’t solved by a single filter. It takes multiple defenses working together to block abuse without hurting the experience for real users. That’s the approach behind WorkOS Radar: a security stack for your sign-up flow, where each layer targets a different kind of risk.

And while the system under the hood is complex, enabling it isn’t. Each layer can be turned on with a simple toggle, giving you enterprise-grade protection without the maintenance burden.

Layer 1: Blocking disposable emails

Disposable email providers (like mailinator.com or 10minutemail.net) make it easy for bad actors to bypass free trial limits. WorkOS Radar maintains a continuously updated blocklist of these domains, shutting them down before they ever pollute your database.

Radar compares the email domain at sign-up against a managed list of thousands of disposable providers. The list updates automatically as new domains appear, so you’re always protected.

Layer 2: Detecting and stopping bots

Traditional CAPTCHAs only catch unsophisticated scripts. Today’s bots simulate real browsers, randomize mouse movements, and even solve CAPTCHAs via third-party services.

Radar analyzes traffic patterns, request headers, and velocity. For example, a single IP firing hundreds of sign-up requests per minute is instantly flagged. This layer neutralizes automated bulk sign-ups that inflate your metrics.

In addition to detecting that the client is a bot, Radar can differentiate between different types of bots, such as AI agents or search engine crawlers, giving developers the ability to control which kinds of bots are restricted.

Layer 3: Preventing repeat sign-ups

Even with disposable emails blocked, determined abusers try again, rotating through IPs, devices, and identities to farm free trials.

When abusers create dozens or hundreds of accounts, they’re often using the same tools, browsers, or environments. Radar sees those connections. It identifies shared device fingerprints, reused IP pools, and identical behavior patterns across seemingly distinct users.

Layer 4: Enforcing compliance with sanctioned countries

Beyond fraud, some sign-ups create legal and regulatory risk. Accepting accounts from U.S.-sanctioned countries can expose you to penalties.

Radar maintains an always-current list of sanctioned regions. Requests from these geographies are blocked at the network edge, reducing risk without requiring manual monitoring from your team.

The power of layered defenses

Each layer raises the cost of abuse. Disposable email blockers filter out casual freeloaders, bot detection stops automated attacks, repeat sign-up prevention handles persistent abusers, and sanctioned-country blocking enforces compliance.

Together, these layers create a defense-in-depth strategy that makes abuse exponentially harder while keeping friction low for real users.

The payoff of high-quality sign-ups

When you focus on sign-up quality, you don’t just reduce risk, you improve your business fundamentals:

• Accurate analytics that reflect real growth.
• Lower support costs from reduced fraud and abuse.
• Better conversion rates as free trials map to genuine customers.
• Peace of mind with compliance handled out of the box.

Instead of chasing down fake users, you can focus on activating and delighting the real ones.

Final thoughts

Abuse at sign-up is one of those problems that only gets harder (and more expensive) the longer you ignore it. By adding protections now, you keep your data, compliance, and growth engine clean.

‍Sign up today and protect your sign-ups with the click of a button.