How Credential Stuffing Attacks Work (And How to Defend)
Neil Hare-Brown- Apr 28
- 3 min read
Credential stuffing is one of the simplest — and most effective — techniques cybercriminals use to breach businesses.
It doesn’t require sophisticated hacking skills. It simply exploits a human habit: reusing passwords across multiple accounts.
Here’s how credential stuffing attacks happen, what risks they pose to your business, and how to defend against them effectively.
What Is Credential Stuffing?
Credential stuffing is when attackers use previously stolen usernames and passwords — often gathered from earlier data breaches — to try and access accounts on different platforms or systems.
If employees reuse passwords across work and personal accounts, attackers can break into corporate systems without ever having to guess or crack anything.
Credential stuffing attacks are typically automated, using bots to attempt thousands of login combinations quickly.
How a Credential Stuffing Attack Unfolds
Step 1: Gather Stolen Credentials
Attackers collect usernames and passwords from previous data leaks, dark web dumps, or phishing campaigns.
Step 2: Automate Login Attempts
Using bots, attackers try the stolen credentials across multiple websites, portals, or corporate login pages.
Step 3: Identify Successful Logins
If login is successful, the account is flagged for takeover, exploitation, or sale.
Step 4: Exploit or Escalate Access
Attackers may steal data, move laterally across systems, or use the access to launch broader attacks like business email compromise (BEC) or ransomware.
Why Credential Stuffing Is So Dangerous for Businesses
✅ High Success Rate:
If passwords are reused, success rates can be alarmingly high.
✅ Hard to Detect Quickly:
Automated traffic can mimic normal login patterns without triggering alarms.
✅ Can Lead to Bigger Breaches:
A single stolen account can provide entry to sensitive systems or cloud services.
✅ Damages Reputation and Trust:
Customers and partners expect businesses to protect accounts rigorously.
Credential stuffing often acts as the first step toward major security incidents, including data breaches, financial theft, and ransomware deployment.
Common Signs of a Credential Stuffing Attack
A sudden spike in failed login attempts
Large volumes of logins from unfamiliar IP addresses
Multiple accounts locked out simultaneously
Reports of account compromise from users or customers
Detection of credential testing scripts in web server logs
If you spot these signs, activate your cyber incident response plan immediately.
How to Defend Against Credential Stuffing
Enforce Strong, Unique Passwords
Mandate unique passwords for every business account — no reusing personal passwords.
Deploy Multi-Factor Authentication (MFA)
Even if a password is stolen, MFA dramatically reduces the chance of a successful takeover.
Use Rate Limiting and Bot Detection
Implement controls that slow or block multiple failed login attempts from the same IP address.
Monitor for Credential Leaks
Use threat intelligence services to monitor the dark web for leaked employee credentials associated with your domain.
Educate Staff About Password Hygiene
Ongoing security awareness training is critical to reinforce why reusing passwords is dangerous.
Run Regular Cyber Exercises
Test your team’s response to account takeover attempts through cyber incident exercising.
How STORM Guidance Can Help
✔ Threat monitoring for stolen credentials
✔ Incident response and account recovery support
✔ Security awareness training for staff
✔ Cloud and identity system audits
✔ Cyber incident exercising and resilience planning
Protect Your Accounts Before Attackers Find Them
Credential stuffing is cheap, easy, and devastating — and it's not going away. By enforcing strong authentication, monitoring for leaks, and preparing your team, you can close one of the most common doors attackers use.
Proactive defences like multi-factor authentication, strong password policies, and early detection make all the difference in keeping your business secure.
For broader cyber resilience strategies and ongoing protection, explore Storm Guidance’s cybersecurity services.
