If you've landed here, something probably felt wrong. A login alert from a country you've never visited. A Steam or Discord account you can't get into. A friend asking why you sent them a link about crypto. Or you downloaded something you now regret and you're wondering what it did.
The short answer: you can find out in about a minute, for free, with Stealer Check. Enter your email address and we'll search the stolen data criminals are trading for it, then email you what we find. The rest of this post explains what "stolen by malware" actually means, why your antivirus and Have I Been Pwned probably didn't warn you, and what to do if the answer is yes.
What an infostealer does to your computer
An infostealer (sometimes written "info stealer") is a small piece of malware with one job. It runs on your computer for a few seconds, copies everything your web browser has saved, uploads it to the criminal who planted it, and usually deletes itself.
"Everything your browser has saved" is more than you think:
- Every saved password, with the site and username it belongs to. Not scrambled. Readable.
- Session cookies, the little tokens that keep you signed in to Gmail, Facebook, your bank, Amazon and Steam so you don't have to log in every time. With a copy of that cookie, someone else is you, no password and no two-factor code required.
- Autofill data: your name, address, phone number and sometimes card details.
- Crypto wallet files and browser extensions.
- A screenshot of your desktop, a list of installed software, and the make and model of the machine.
That bundle is called a stealer log. Criminals sell them individually, trade them by the thousand, and give older ones away free as advertising. Constella Intelligence counted over 51 million of them in 2025 alone. DarkStrata holds more than 200 billion stolen credentials collected from logs and breaches, which is what Stealer Check searches.
How you probably got infected
Nobody chooses to install malware, but almost everyone who gets infected chose to run something. The usual routes:
- Cracked software and game cheats. The "free" Photoshop, the aimbot, the mod pack from a Discord link. This is the single biggest source of infected home computers.
- Fake downloads from search ads. You search for a popular program, click the sponsored result at the top, and get a lookalike site serving a poisoned installer.
- "Prove you're human" pages that ask you to press Windows+R and paste something. That pastes a command that fetches the stealer.
- Files from strangers on Discord, Telegram or email: a "game beta", a "portfolio", a "contract".
If one of those rings a bell, go and check your email address now, then come back.
Why your antivirus said nothing
Modern stealers are built to run once and vanish. By the time an antivirus signature exists for that week's build, the log has already been uploaded and the malware has removed itself. A clean scan today tells you about today. It tells you nothing about the thirty seconds six weeks ago when your browser was copied.
The stolen data, on the other hand, is permanent. It sits in a log that gets copied from seller to seller. That's why the reliable way to know whether you were a victim is not to scan your computer but to search the logs.
Why Have I Been Pwned didn't warn you either
Have I Been Pwned is excellent and you should use it. But it answers a different question. It tells you which companies lost a copy of their customer list, usually with your password scrambled, often years ago. Change that one password and you're done.
A stealer log isn't a company's breach. It's your computer's. Every site, every password, every signed-in session, taken at once. Changing one password doesn't fix it, and the detail in a log (which sites you use, your usernames, which machine) is far too private to show on a public web page. That's why Stealer Check emails the result to the address you check and nowhere else. Only someone who can open that inbox ever sees it. We've written more on the difference in What are stealer logs?
How to check if your passwords were stolen
- Go to darkstrata.io/en/stealer-check.
- Type your email address. Any address, personal or work. The page never says whether it was found.
- Open your inbox. Within a few minutes you'll get the result, whether or not we found anything.
If you're in a log, the email tells you the malware family, when it was captured, and which services had saved logins taken. With a free account you can also see which device it came from, how many session cookies were copied, and each password masked (enough to recognise it, never the whole thing). It is free, there's no card and no sales call, and you can keep the address monitored so we email you if it turns up in a new log.
You can't check someone else's address. Typing it in only sends them a confirmation. If you're worried about a parent, partner or a friend who loves "free" games, send them the link.
What to do if the answer is yes
The order matters more than the speed. If you reset every password from a computer that's still infected, you've just handed the criminal a fresh set.
- Clean the device first. Run a full scan with a reputable antivirus. Delete the cracked software or cheat that let it in. If in any doubt, back up your files and reinstall Windows.
- Sign out everywhere. Google, Microsoft, Apple, Facebook, Discord, Steam and your bank all have a "sign out of all devices" button in their security settings. This kills the stolen cookies. Do it before changing a single password.
- Change passwords, from a clean device, email first. Your email account resets everything else, so it goes first. Then every service in the result, then anything that shared a password with them.
- Turn on two-factor and check recovery. Prefer a passkey or an authenticator app over text messages. Look in your email settings for forwarding rules or recovery addresses you didn't add. Criminals leave back doors.
The full walkthrough, with screenshots of where each setting lives, is in our infostealer infection guide.
Was it a work laptop?
Here's the part most people don't think about. If the infected machine had your work email, VPN or Teams signed in, your employer's accounts were in that log too. Criminals filter logs by company domain specifically to find that, and the working corporate login inside a ten-dollar log is how a lot of ransomware attacks start.
Tell your IT team. And if you are the IT team, or the person who'd get blamed, DarkStrata's free domain check does for your whole company what Stealer Check does for one address: enter a work email and we search for every exposed credential on your domain, then email an exposure report. From there, continuous monitoring alerts you within hours of a staff or customer credential appearing in a new log, tells you which machine was infected and whether session cookies were taken, and lets the person affected fix it privately through Lens without a manager reading their personal passwords.
Common questions
Is it really free?
Yes. Checking, the result, and ongoing monitoring of your address cost nothing. Businesses pay for domain-wide monitoring, which funds the free personal check.
I got a clean result. Am I safe?
It means your address isn't in the logs we hold. It doesn't mean it's never been taken. Leave monitoring on, and if you know you ran something dodgy, follow the clean-up steps anyway.
Will you show me my password?
Never by email. In a free account, each password is masked: enough to tell which one it was, not enough to use.
What do you store about me?
The address you asked us to check, for 30 days, or for as long as you keep it monitored. You can delete it yourself at any time. Details are in our privacy policy.
The one-minute version
If malware ran on your computer, it copied your browser and sold it. Your antivirus won't tell you, and breach checkers can't. Stealer Check searches the stolen data itself and emails you the answer, free. If it finds you: clean the device, sign out everywhere, then change passwords from a clean machine. Go and check your email address. It takes less time than reading this did.