What is a data breach?
2 min read · Updated October 15, 2026
A data breach is an incident where information is accessed, copied or exposed without authorisation. It can happen through hacking, stolen credentials, misconfigured databases or insider mistakes. Leaked data often includes email addresses, passwords, names and phone numbers, which criminals reuse for phishing and account takeover.
How data breaches happen
- ✓Hacking: attackers exploit a software flaw to reach a company’s database.
- ✓Stolen credentials: employee logins obtained through phishing or malware open the door.
- ✓Misconfiguration: a database or cloud storage left open to the internet without a password.
- ✓Third-party failure: a supplier or partner is breached and your data goes with it.
- ✓Human error or insiders: files sent to the wrong recipient, or staff copying data they should not.
What kind of data is exposed
It depends on the company. Typical records include email addresses, usernames, hashed or plaintext passwords, full names, phone numbers, physical addresses, dates of birth and sometimes partial payment or ID details.
Even a basic record, just an email and a hashed password, is valuable. An email address links your identity across services, and a password, if cracked or reused, can open other accounts.
Find out if your email is in a known breach
Run the free Leakill check. No password needed, no signup, and you see the result in seconds.
Why old breaches still matter
Leaked data does not expire. Records from a breach years ago are sold, traded and combined with newer leaks. Attackers run huge lists of email and password pairs against popular sites in a technique called credential stuffing. If you reused a password that was leaked in an old breach, an account you created much later can still be at risk.
How to find out if you were affected
Companies are supposed to notify affected users, but many breaches are discovered by researchers and never reach your inbox. The practical approach is to check your addresses with a breach lookup tool and to watch for official notices. Leakill’s free check shows whether your address appears in known breach records.
Frequently asked questions
What is the difference between a data breach and a data leak?+
In everyday use they overlap. A breach usually implies an attack, while a leak often means data was exposed by mistake. The consequences for you are similar.
Are passwords always exposed in a breach?+
No. Some breaches only include emails or personal details. When passwords are included they may be hashed, which makes them harder (not impossible) to crack.
Can I get my data removed from a breach?+
Not once it has circulated. You can reduce the damage by changing affected passwords, enabling 2FA and watching for scams.
Stop guessing. Check your email in seconds.
The free Leakill check looks for your email address in known breach records and tells you whether it was exposed. If it was, an optional detailed report lists the incidents, dates, sources, the kinds of data involved and practical next steps. It is a one-off report, not a subscription.
A breach match is a warning signal, not proof that someone has access to your account today. No public database covers every breach, so a clean result lowers risk without guaranteeing safety.