Account Takeover (ATO) is a form of cyberattack where malicious actors gain unauthorized access to user accounts—typically through automated bots. Once these attackers seize control of an account, they can use it for fraudulent purposes, such as stealing stored funds, making unauthorized purchases, stealing identity or credit card information, or even launching further attacks on other users or systems.

How Does an ATO Attack Work?

The most common method attackers use in ATO attacks is credential stuffing. This technique relies on bots to try vast numbers of username and password combinations—often sourced from previously breached databases. Since a lot of users reuse the same passwords across multiple sites, attackers only need a few hits to take over several accounts.

In a typical credential stuffing attack:

1. Bots test thousands of credentials by attempting logins across multiple accounts.
2. Eventually, the attacker accesses the accounts using compromised username-password pairs.
3. Once inside, they can perform activities such as making fraudulent transactions, stealing personal data, or exploiting stored value.

These attacks often go unnoticed for some time because the volume of failed login attempts might look like normal activity, especially if the attack is spread across different accounts.

The High Cost of Account Takeover

ATO attacks can be devastating both for businesses and individuals. According to a report by IBM, stolen or compromised credentials are the leading cause of data breaches, and they take the longest to identify—on average, it takes 327 days for businesses to discover such breaches. This delay allows attackers to inflict significant damage before the issue is even detected.

Preventing Account Takeover

Although multi-factor authentication (MFA) is widely used to prevent ATO attacks, it is not a complete solution. Skilled attackers can bypass MFA using methods like SIM swaps, hijacked authentication APIs, or social engineering tactics. To fully protect against ATO attacks, businesses need a multi-layered defense strategy that goes beyond just MFA.

Here are some of the most effective strategies for preventing ATO attacks:

1. Implement Multi-Factor Authentication (MFA)

While MFA isn’t foolproof, it provides an essential extra layer of security. Requiring a second form of authentication, such as a temporary code sent to a user’s device, makes it more difficult for attackers to access accounts with just a password.

2. Use Behavioral Analytics

Behavioral analysis can help identify suspicious activity by monitoring how users interact with your website or app. For example, if a bot is trying to log in by testing multiple password combinations, it will likely behave differently from a real user. Using this analysis, businesses can flag suspicious login attempts and block them before they lead to an ATO.

3. Device and Browser Fingerprinting

By analyzing the device and browser characteristics used to access accounts, businesses can create a “fingerprint” for each user. If a login attempt is made from an unfamiliar device or browser, this can trigger an alert or additional authentication steps, making it difficult for bots to log in from unknown devices.

4. IP Reputation Monitoring

Tracking and analyzing the reputation of IP addresses is another key defense. Many ATO attacks come from known malicious IP addresses or regions. By blocking login attempts from suspicious or blacklisted IPs, businesses can prevent ATO attempts before they even start.

5. Rate Limiting and CAPTCHA

Rate limiting controls how many login attempts a user can make in a short time frame and CAPTCHA challenges help to block automated bot attacks, as bots struggle to solve CAPTCHA puzzles.

6. Regular Security Audits and Monitoring

Routine audits of your security systems and frequent monitoring of account activity are essential to identifying vulnerabilities and detecting attacks early. Businesses should regularly check for suspicious login attempts, account changes, or anomalies in user behavior that could indicate an ATO attack in progress.

Conclusion

Account takeover (ATO) is a significant threat to both businesses and their customers. Automated bots testing credentials, combined with the vast amount of stolen login information available on the dark web, makes it all too easy for attackers to gain unauthorized access to user accounts.

To protect against ATO attacks, businesses must adopt a multi-faceted approach to security that includes multi-factor authentication, behavioral analytics, device fingerprinting, and IP reputation monitoring. By proactively defending against credential stuffing and other ATO techniques, companies can better protect their users’ accounts and data from being compromised.