Stop Credential Stuffing, Session Replay & Account Takeover
Attackers replay stolen credential lists through rotating residential proxies and hijacked sessions through antidetect browsers — so every attempt reaches /login looking like a real user on a clean IP. Sentinel checks the network and device behind each login invisibly, in under 40ms.
What you're up against
Credential stuffing behind residential proxies
Stolen credential lists get replayed through rotating residential proxies, so every attempt arrives from a different clean home IP. Rate limits and IP blocklists key on exactly the thing the attacker rotates for free.
Stolen sessions replayed in antidetect browsers
Attackers import hijacked cookies into Kameleo or GoLogin and impersonate the victim's browser well enough to pass naive fingerprint checks. The session token is genuine — only the environment replaying it gives the attack away.
Automation that paces itself like a human
Headless browsers with stealth patches spread attempts across hours and thousands of exit IPs, staying under every velocity threshold. By the time login-failure dashboards show a spike, most of the list has already been tested.
Takeovers you learn about from support tickets
A successful takeover looks like a normal login in your logs. You find out when the victim writes in — after the email was changed, the payout redirected, or the stored card used — and each of those tickets costs trust a refund won't win back.
What Sentinel does for you
- See the network behind every login attempt — residential proxy, VPN, datacenter, or Tor — not just the IP
- Detect antidetect browsers and automation on /login before a session is issued
- Link one device to the many accounts it touches — the signature of tooling working a stolen list
- Catch the new-device + VPN + automation combination on established accounts — the classic takeover shape
- Score every login in under 40ms — no CAPTCHAs, no step-up friction for legitimate users
reduction in fake account registrations at an EU fintech — caught with the same VPN, antidetect, and automation signals that expose takeover attempts at login
[ Read Full Case Study ]Where the check goes
One call site matters most: login, after credentials validate but before you issue a session — that is where credential stuffing and replayed sessions surface. Add the same check to password reset and to sensitive post-auth actions like email or payout changes, where a successful takeover actually does its damage. The client snippet rides along on the page; the server asks Sentinel for a verdict before your session logic runs.
// After credentials validate, before the session is issued
const res = await fetch('https://sntlhq.com/v1/evaluate', {
method: 'POST',
headers: {
'Authorization': 'Bearer ' + process.env.SENTINEL_KEY,
'Content-Type': 'application/json'
},
body: JSON.stringify({ token: req.body.sentinel_token })
});
const risk = await res.json();
if (risk.decision === 'block') return res.status(403).json({ error: 'Request rejected' });
if (risk.decision === 'review') flagForReview(risk.reasons);The signals that matter here
Network context on every attempt. Credential-stuffing runs rent rotating residential proxies precisely so that every attempt arrives on a clean home IP no blocklist has seen. Sentinel classifies the network behind each request — residential proxy, VPN, datacenter, Tor — so a stuffing run reads as what it is: hundreds of never-seen devices arriving through rotating residential exits, not hundreds of returning customers.
One device, many accounts. Takeover tooling works a stolen list from one machine. Sentinel keys its cross-browser "times seen" counter to a hardware-level device ID, so every account a single device logs into within your app links together — and the fiftieth account touched by the same laptop stands out even when each attempt arrives from a different IP and a fresh browser profile.
The ATO shape: new device, VPN, automation. An account that has signed in from the same laptop for a year suddenly authenticates from a first-seen visitor_id, over a VPN, with automation_detected in the reasons array. Any one of those signals is survivable; the combination on an established account is the takeover pattern, and the one worth routing to review or step-up rather than silently allowing.
Replayed sessions, exposed by the environment. A stolen session cookie is genuine; the browser replaying it is not. Antidetect browsers importing victim cookies leave measurable artifacts, which Sentinel surfaces through device.antidetect and the tampering_score — and because the verdict is an API response rather than a challenge, the account's real owner never sees a CAPTCHA.
Common questions
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Free tier: 1,000 requests/hour. No card, no expiry. Detects residential proxies, antidetect browsers, and AI bots.