Why is it dangerous to use the same password everywhere? Link to heading

It’s easier to remember one password. That’s understandable. But if you use the same password for your banking app, your email, and a forum you haven’t visited in a long time, a single data breach is enough to compromise all your accounts.

What is credential stuffing? Link to heading

When a website is hacked, the leaked username-password pairs quickly end up on the dark web. Attackers use automated programs to try these lists on other sites - this is called credential stuffing.

The logic is simple: if your password has been leaked on a small forum, the attacker will try to use it to log into your Gmail, online banking, and social media accounts. Unfortunately, the chances of this happening are not negligible.

How big is the problem really? Link to heading

The HaveIBeenPwned database currently lists more than 14 billion leaked accounts. Almost everyone is affected to some extent - often from sites they don’t even remember visiting.

Some well-known cases:

  • LinkedIn (2012): 117 million account passwords leaked
  • Adobe (2013): 153 million accounts
  • RockYou2024 (2024): nearly 10 billion passwords in one file

These lists are publicly available. Attackers just need to download them.

A real-life scenario Link to heading

  1. You register with a small online store in 2018, using the same password you use everywhere else
  2. In 2020, the online store is quietly hacked and its database is leaked
  3. In 2024, an automated program tries the email + password combination on Gmail
  4. It works. From there, it accesses your bank notifications, password reset emails, everything.

You don’t have to be a target. This happens automatically, on a massive scale.

What can you do about it? Link to heading

Use a unique password for each account. This is the only real defense. If one password is leaked, your other accounts remain secure.

Of course, this means a lot of passwords - it’s impossible to manage them all from memory. That’s what password managers are for: they collect all your other randomly generated passwords behind a single strong master password. We’ll talk about this in a separate post.

In the meantime, it’s worth checking this website to see if your email address has been involved in a known data breach: haveibeenpwned.com

Summary Link to heading

A reused password is like a universal key - if someone gets it, they can open every door. Unique passwords are not inconvenient if you manage them with a password manager. The next step is to learn how they work.

This article is part of a series that aims to explain the basics of online security in simple terms.