Credential Stuffing
Somebody buys a list of other people's passwords, points a script at your login page, and calls this a business. Thousands of combinations get tested every hour, and the overwhelming majority fail, which costs our entrepreneur nothing at all.
The small percentage that succeed are the problem: real accounts, belonging to real customers, now in somebody else's hands.
Traditional defenses barely slow the script down. Dregs recognizes the attack for what it is while it's still running, and flags the accounts that fell to it.
The Credential Stuffing Attack Vector
Data breaches are constant. Billions of username/password pairs are circulating on the "dark web", and attackers know that a significant percentage of people reuse the same password across multiple services. Credential stuffing exploits this vulnerability at scale. Automated scripts gather leaked credentials from one breach and test them against every login form they can find... including yours.
The math works in the attacker's favor, which is the entire appeal for a line of work requiring no talent whatsoever. Even a 0.1% success rate on a list of 100,000 credentials means 100 compromised accounts. The overheads are a cloud VM, a proxy list, and an off-the-shelf stuffing tool bought from somebody equally idle. The credentials are often free.
Then the arithmetic stops being funny. Each of those hundred accounts belongs to a customer who did nothing wrong beyond reusing a password, and who is about to discover that their saved payment details, private data, and good name are being spent by a stranger.
The standard defenses in most web applications aren't designed for this type of attack.
| The Traditional Defense | Why It Often Fails |
|---|---|
| IP rate limiting | Distributed botnets spread the attempts across thousands of residential IPs, keeping each address comfortably under your thresholds. The attack is enormous in aggregate while every individual IP looks polite. |
| Account lockout | Lockouts punish the victims rather than the attacker. A stuffing run against your user base locks legitimate customers out of their own accounts, turning the attack into a denial of service you administered yourself. |
| Password complexity rules | Complexity rules govern how passwords are made, not where they've been. The password being tested is often perfectly strong; it's just also the password the customer reused on a site that got breached. |
| WAFs | Signature-based rules recognize attacks that have been seen before. A low-and-slow run with rotating IPs and a current browser fingerprint stays inside every signature and under every rate limit. |
| Login CAPTCHAs | A login CAPTCHA adds friction to every legitimate sign-in, while solving farms clear them for fractions of a cent. The attacker's economics barely move; yours do. |
These traditional defenses either punish your real users with false positives, fail against distributed attacks, or both. You need detection that looks at what the visitor actually is, not just what they're doing on a single request.
How Credential Stuffing Threatens Your Business
A significant credential stuffing campaign doesn't just compromise a few accounts. It creates cascading damage across your entire operation.
Account takeover
Compromised accounts may lead to fraud, unauthorized purchases, data theft, and legal liability. Each taken-over account is a breach incident that may trigger notification obligations, depending on your jurisdiction and what data was breached. Dregs detects the takeovers themselves, not just the attack wave.Lost customer trust
Users who discover their account was accessed by someone else lose confidence in your platform. Even if it was ultimately their fault for reusing credentials, the trust damage ultimately extends far beyond the directly affected accounts.Operational burden
Support tickets flood in. Incident response teams scramble. Forced password resets frustrate users who weren't even affected. Every credential stuffing incident costs engineering, support, and leadership time that should be spent building your product.How Dregs Detects Credential Stuffing
A credential stuffing attack looks very different from normal login behavior, even when the credentials are correct. The password might match, but the visitor behind it has a profile that no legitimate user would produce. Dregs sees the attack from multiple angles at once, and every score opens into the observations behind it, so you can see exactly why a session was flagged.
Login Velocity
This is the most distinctive signal. A real user logs in once and then uses your product. A stuffing attack submits dozens of login attempts per minute, each with different credentials, with mechanically consistent timing between them. The Behavior score measures this velocity directly. Even "slow" stuffing attacks that add randomized delays between attempts still produce a session that contains nothing but login form submissions, a pattern that's impossible to disguise.
Identity Cycling
Normal users have one identity per device. A credential stuffing tool has hundreds. Device fingerprinting makes this inverted relationship immediately visible because the same fingerprint appears in login events for username after username after username. No amount of IP rotation or user-agent spoofing changes the underlying device, so the pattern can persist even when the attacker tries to disguise the source.
Automation Detection
The tools used for credential stuffing (headless browsers, HTTP libraries, automation frameworks) leave signs that are difficult to fake convincingly. The Humanity score catches impossible hardware profiles, missing browser APIs, and rendering inconsistencies. Even sophisticated tools running inside real browser instances produce subtle fingerprint differences that Dregs can detect.
Cross-Account Signal
The Uniqueness score captures the broader pattern. When a single device appears in login events for hundreds of different usernames in a short window, that's the opposite of how real users behave. This cross-identity signal is visible even when individual login attempts look normal in isolation. It's the aggregate that gives the attack away.
Example: Handling a Credential Stuffing Attack
Here's what it looks like when a credential stuffing campaign targets your login page in the middle of the night:
The attack was detected and stopped within a minute. Any accounts that were successfully accessed during that window can be automatically flagged for forced password reset.
Mitigating Credential Stuffing Attacks
Detection is only half the equation. Once Dregs identifies a credential stuffing attack, your team needs to act on it fast. Different stages of the attack call for a combination of automated and manual responses.
Session blocking
Terminate and block affected sessions immediately. The stuffing tool loses its connection and has to start over from scratch, if it can get past detection again at all. This is the fastest way to stop an active attack and protect other user accounts that haven't been breached yet.
Account protection
Force an immediate password reset on any account that was successfully accessed during the attack. Notify the affected users. Invalidate existing sessions. Act quickly to limit the damage window and prevents the attacker from using compromised credentials later.
IP blocking
Block the source IP address or range at the network level. While sophisticated attackers rotate IPs, many credential stuffing operations use a limited pool. Quickly blocking the bad IPs reduces the volume of attempts and forces the attacker to burn through their proxy infrastructure faster.
Dregs can notify your team with escalations and webhooks, depending on your preferred notification channels. This gives you a chance to react quickly to credential stuffing attacks and other suspicious activity, with less manual review: the badge and escalation arrive with the evidence already assembled. Get notified quickly, whether the attack happens at 2 AM on a Tuesday or noon on a holiday.
Credential stuffing is one specific form of bot attack. Dregs detects the underlying automation regardless of the objective, so the same integration that stops credential stuffing also catches unwanted scrapers, spam bots, and fake account bots.
Stop credential stuffing before accounts get compromised.
Dregs detects suspicious activity like automated login attacks so your team can respond quickly. Install the tracking script and start protecting your site.
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