The True Cost Of Weak Passwords: 4 Catastrophic Breaches That Hit Hard

The True Cost Of Weak Passwords: 4 Catastrophic Breaches That Hit Hard; Password pandemonium: The simple mistakes fueling the biggest data breaches

Key Points:
Cybersecurity expert explores how weak passwords continue to drive the world’s biggest data breaches
Expert examines four major cases, including a 16 billion password leak and McDonald’s and Yahoo data breaches, and explains why weak passwords remain so widespread, naming the most common offenders
Expert outlines straightforward steps for better security, urging readers to embrace password managers, unique logins, and two-factor authentication
It feels like we hear about cyberattacks and data breaches almost every day. Behind these headlines, we often find the same old culprit: weak passwords.

From reusing the same login across dozens of platforms to setting “123456” as the only line of defense, poor password habits continue to leave billions exposed. With 94% of passwords used to access multiple accounts and only 3% meeting basic complexity standards, cybercriminals barely need to lift a finger to hack into sensitive accounts.
Leading the charge against cybersecurity negligence is Danny Mitchell, a cybersecurity expert and writer for Heimdal Security.

Below, he reveals how a single mistake can snowball into a massive data breach and offers individuals and businesses advice on how to protect their accounts.
4 Infamous Password Fails That Made Headlines

1. The 16 Billion Password Mega Leak

In June 2025, the internet was rocked by one of the largest data dumps in history: a staggering 16 billion stolen passwords and credentials from dozens of past breaches combined into a single leak. While some were recycled from previous incidents, millions were newly exposed. The breach revealed just how reckless password reuse has become, with “admin” and “password” appearing tens of millions of times.
The fallout was swift, as credentials flooded dark web markets, selling for as little as $10 apiece. Hackers could buy access to social media, email, and even bank accounts for the price of a takeaway coffee.

2. McDonald’s Monopoly VIP Mishap

McDonald’s UK faced an embarrassing blunder during its Monopoly VIP prize campaign in 2025. Due to an administrative error, database usernames and passwords were accidentally emailed to prize winners, exposing credentials for both staging and production servers. While the production system was firewalled, some recipients were able to access the staging server, a near miss that could have been catastrophic.
“Even global brands can slip up when it comes to basic digital hygiene,” says Mitchell. “A single misconfiguration or forgotten password rule can put entire networks at risk. What saved McDonald’s was the ethical behavior of the individual who reported it responsibly.”
The company acted fast, changing credentials and apologizing publicly. Still, the incident served as a costly reminder that technical mistakes can travel at the speed of email: instantaneously.

3. The Louvre Password That Made France Blush

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In one of this year’s more surreal cybersecurity muck-ups, a 2014 security report resurfaced, revealing that the Louvre’s CCTV network password was simply “LOUVRE.” The detail came to light after an audacious jewel heist targeted the museum in 2025, reigniting debate about lax password policies in high-security institutions.
Though the break-in itself involved angle grinders, not hacking, the discovery became a national embarrassment. “Weak passwords might not always be the weapon, but they’re an open door,” says Mitchell. “If your digital security looks lazy, criminals assume your physical defenses are too. And in this case, they were right.”

4. Yahoo’s Billion-Dollar Breach

Between 2013 and 2016, Yahoo suffered a series of cyberattacks that exposed 3 billion user accounts, one of the largest known breaches in history. Hackers gained access to sensitive information, including names, phone numbers, birth dates, and security questions, through stolen backups and database infiltration.
Yahoo’s delayed disclosure led to $35 million in fines and 41 class-action lawsuits, as well as a significant dent in public trust when the breach was fully revealed during Verizon’s 2017 acquisition of the company.
“Transparency, speed, and strong password encryption could have prevented years of fallout that tarnished Yahoo’s reputation,” says Mitchell. “It proved that password negligence can alter the fate of entire companies.”
Why Weak Passwords Still Dominate: The Top 10 Offenders
Despite years of public warnings, users continue to rely on weak passwords. According to NordPass, the average person has over 160 accounts. Remembering strong, unique passwords for all of them is nearly impossible, so as a result, users fall back on simple, predictable combinations like “123456” or “password.”
It’s child’s play for hackers to guess these simple passwords using brute-force attacks, a method in which they enter common password variations in the hope that one will work. Brute-force attacks clearly work wonders, as they account for 37% of cyber breaches today.
“Hackers don’t need advanced tools anymore,” says Mitchell. “They just automate password attempts using bots, which try the same 10,000 simple passwords that people keep recycling. It’s shocking how often it works.”
Businesses aren’t immune; NordPass’s data shows that the most common passwords used for corporate accounts are almost identical to personal ones. This means employees are logging into sensitive company systems with passwords that could be cracked in seconds.
Below, Mitchellpresents the 10 most common weak passwords still being used in 2025 (which you should definitely avoid):
123456
123456789
12345678
password
qwerty123
qwerty1
111111
12345
secret
123123
These familiar offenders are short, predictable, and lack symbols or capitalization, all of which make them easy for automated systems to guess. According to Verizon’s 2025 Data Breach Report, passwords like these can be cracked in under a second.
Danny Mitchell, Cybersecurity Writer at Heimdal Security, commented:
“Most cyberattacks start with someone making a simple mistake. The truth is, even the most advanced security systems can’t help if your password is ‘123456’.
“Effective password management is a much more dependable way of protecting sensitive accounts than memorizing complex strings of numbers and letters. That’s why I recommend using a password manager, as these tools generate strong passwords and, most importantly, remember them for you.
“Using unique passwords for every account should be a no-brainer, but you’d be surprised how many times people forget this simple step. Avoid patterns or personal clues; birthdays, pet names, or “qwerty” sequences are the first things hackers try.
You should also enable two-factor authentication (2FA) wherever possible. This simple extra step adds a protective layer even if your password is stolen.
“Finally, remember to check for breaches regularly. Tools like ‘Have I Been Pwned’ can tell you if your credentials have appeared in leaked databases.
“The ‘intention vs. action’ gap remains one of cybersecurity’s biggest challenges. Most people say they’ll change their passwords after a breach, but only about a quarter actually do. But passwords are your first and often your only line of defense, so take them seriously, and you’ll immediately remove one of the biggest entry points for attackers.”