Most data breaches start with something simple: a stolen password, an unpatched server, or an employee clicking the wrong link.
• Stolen credentials cause most data breaches. Attackers don’t break in when they can just log in with leaked passwords
• Infostealer malware captures passwords, session tokens, and autofill data before encryption and sells them on criminal markets within hours
• Third-party and supply chain breaches are growing fast because one compromised vendor can expose thousands of organizations
• Data breach prevention requires layered defenses: credential monitoring, MFA, patch management, access control, and a tested response plan
Over 53 billion identity records were exposed on the dark web in 2024. That’s not a scare tactic. It’s the actual volume of stolen credentials, personal data, and session tokens circulating across criminal marketplaces.
If your organization stores sensitive data, there’s a good chance you’ll experience a breach at some point. Understanding what causes data breaches is the first step toward preventing them.
This guide breaks down the five most common causes, shows you real-world examples, and gives you a practical prevention checklist.
Data breach is a security incident where an unauthorized party accesses sensitive, protected, or confidential data. Also called a cybersecurity breach or cyber breach, the attacker may steal, disclose, or hold the data for ransom.
A data breach can happen to any organization that stores sensitive information. After gaining access to the data, a threat actor may attempt to steal, disclose it, or extort the data owner for financial gain.
Data breaches can include data types like personal information (e.g., social security numbers), financial data (e.g., credit card numbers), intellectual property, trade secrets, and other sensitive information. This kind of data theft often leads to identity theft for affected individuals. It’s important to note that both small businesses and enterprises are targets, with healthcare and financial services among the most frequently hit industries.
Organizations handling sensitive data are responsible for protecting it. The organization is legally held responsible if a threat actor gains unauthorized access to sensitive data. Once a data breach occurs, the repercussions can be severe, including financial loss, damage to reputation, legal consequences, and a loss of public trust. For this reason, organizations invest heavily in data breach prevention and risk management to mitigate their impact if and when they occur.
Real-world data breach examples show just how costly these incidents get. The 2023 MOVEit supply chain breach exposed data from over 2,600 organizations. The 2024 Change Healthcare breach affected 100 million patient records. In both cases, stolen credentials or unpatched vulnerabilities gave attackers their initial access.
Although the terms “data breach” and “data leak” are often used interchangeably, they have two distinct meanings. Data breaches are often the result of a deliberate attack by cybercriminals who exploit vulnerabilities in their target to gain access to the data.
The method of attack can involve hacking, malware attacks, or social engineering. The critical aspect of a data breach is an active, intentional effort by an unauthorized party to access data.
A data leak, on the other hand, refers to unintentional or accidental exposure of confidential information. Leaks often occur due to internal errors, such as misconfigured databases, unsecured servers, or inadvertent employee actions (like sending sensitive information to the wrong person or leaving documents unsecured).
While cybercriminals can exploit leaked data once exposed, the initial exposure is not usually the result of a targeted attack.
Credential stuffing is an attack where criminals use stolen username and password pairs from one breach to try logging into other services. It works because people reuse passwords across multiple accounts. Automated tools can test millions of credentials against a target in minutes.
According to the Verizon Data Breach Investigations Report, 86% of breaches involve using stolen credentials. Cybercriminals steal usernames and passwords from sources such as infostealer malware, 3rd party breaches, and social engineering.
Although counter-intuitive, password complexity and forced password rotation aren’t effective defenses for leaked passwords. In the case of infostealers, the malware captures the plaintext password before they’re encrypted in transit and sends it to the threat actor.
To help protect your accounts, use a password manager and have it generate unique passwords for you. Ensure your system is fully patched and enable Multi-factor Authentication (MFA) wherever available. Infostealers can often bypass standard antivirus solutions, so running periodic system cleaner scans in parallel is essential.
Malware is malicious software that can not only steal credentials and session tokens (to bypass MFA) but has complete access to your device. It can steal, encrypt, and delete files and even take screenshots. Malware is a broad term that includes viruses, worms, trojan horses, spyware, keyloggers, rootkits, adware, and ransomware attacks.
A common strain of malware that is very often used to gain initial access is Infostealer malware. The image below shows an example of the directory structure within the stealer logs. The malware collects sensitive data like browser autofills, session cookies, browsing history, and plaintext passwords captured before they’re encrypted.
There are several steps you should take to protect your systems against malware. It’s essential to keep your antivirus up to date, avoid pirated software, and ensure your software is fully patched. In addition, segmenting your network will help contain the malware in case of a security breach.
Any significantly complex piece of software will have security vulnerabilities at some point. Security researchers and vendors regularly discover issues and create patches to help mitigate the risk before the vulnerabilities are exploited.
There tends to be a lag between when a vulnerability is discovered and when the software gets patched. It takes an average of 38 days to patch a vulnerability. This leaves a large window of opportunity for attackers to reverse engineer a security patch, create a working exploit, and find victims who haven’t applied the fix yet.
Where applicable, enable any automated patching systems available. Depending on the environment, patches may need testing in a controlled environment before widespread deployment. Conduct regular audits to locate any gaps in the patch management process. Finally, ensure you have backups and a regularly tested recovery plan to restore systems to their pre-patch state if required.
Third-party data breaches happen when sensitive data is stolen from a 3rd party vendor who stores data related to your organization. Supply chain attacks are growing fast because one compromised vendor can expose thousands of downstream customers. In many cases, the breach starts with an employee who created an account with the vendor using their work email account.
Many people reuse the same passwords in multiple locations. Password reuse often enables an attacker to use a password leaked on a 3rd party app within your organization.
Require Multi-factor authentication (MFA) to access company resources. MFA mitigates the risk of leaked credentials from 3rd party breaches because a valid username and password are no longer enough to authenticate. In addition, encourage employees to use a password manager to store and generate all their passwords.
Social engineering is a tactic cybercriminals use to manipulate their victims into divulging sensitive information that can be used for fraud. Unlike traditional hacking that relies on technical exploits, social engineering exploits human psychology and the tendency to trust.
Human error is often the weakest link when it comes to cybersecurity. Malicious users exploit phishing scams, pretexting, baiting, vishing, and smishing to trick users into performing specific actions or sharing sensitive data.
While security awareness training can be helpful, organizations should implement technical controls that prevent users from being able to make bad decisions.
A classic example of a phishing email from a bank is shown below. While the email looks like an official email from a (fictional) bank, it’s essentially trying to trick the recipient into clicking the link and submitting their credentials to a site run by the attacker.
Understanding how data breaches happen makes you better equipped to prevent them. Breachsense monitors the dark web for the same data that cybercriminals exploit to gain unauthorized access to your organization. Our platform alerts you whenever any relevant data surfaces so that your security team can prevent an attack before criminals use it.
By taking a proactive approach to security, Breachsense empowers you to be one step ahead of cybercriminals. Don’t wait until it’s too late to secure your data.
Stolen or weak credentials cause the majority of data breaches. The Verizon DBIR consistently shows that over 80% of breaches involve compromised passwords. Attackers get these credentials from infostealer malware, phishing attacks, and third-party breaches where employees reused passwords.
Data breaches typically happen through five main vectors: stolen credentials, malware infections, unpatched software vulnerabilities, third-party vendor compromises, and social engineering attacks like phishing. In most cases, attackers take the path of least resistance by logging in with stolen passwords rather than exploiting technical vulnerabilities.
The 2021 Colonial Pipeline attack started with a single compromised VPN password and shut down fuel delivery across the eastern US. The 2023 MOVEit breach exploited a software vulnerability and hit over 2,600 organizations. The 2024 Change Healthcare breach affected 100 million patient records. In each case, credential monitoring or faster patching could have prevented the initial access.
You can’t eliminate all risk, but you can prevent most credential-based breaches. Use a password manager, enforce MFA, monitor for leaked credentials on the dark web, patch software promptly, and train employees to recognize phishing. A data breach response plan also helps contain incidents faster when they do occur.
Reset all compromised credentials immediately. Investigate the scope of the breach by reviewing access logs. Notify affected individuals and regulators as required by law. Contain the attack by isolating affected systems. Then conduct a post-incident review to close the vulnerability that allowed the breach.
The median time to detect a breach is 11 days according to the 2025 Verizon DBIR. Some breaches go undetected for months. Dark web monitoring can cut detection time dramatically by alerting you when stolen credentials appear on criminal markets, often within hours of the theft.
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