How Account Takeover (ATO) Attacks Are Forcing a Rethink of Authentication

As organizations expand their digital ecosystems, Account Takeover (ATO) attacks have intensified, exploiting vulnerabilities in traditional authentication methods. Cybercriminals increasingly leverage AI-generated deepfakes, automated credential stuffing, and sophisticated fraud tools to bypass security measures. With high-profile breaches on the rise, reliance on passwords and two-factor authentication (2FA) is proving inadequate. Let’s examine these evolving threats and explore the security measures needed to defend against them.

What is Account Takeover?

Account Takeover Definition

Account Takeover is a form of cyberattack in which a malicious actor illicitly gains control over a legitimate user’s account across various digital platforms—including banking, email, social media, and business applications. Unlike conventional credential theft, ATO is characterized by sustained unauthorized access, allowing attackers to manipulate accounts for prolonged periods without detection.

Once an account is taken over, the attacker can:

• Change account details (email, phone number, passwords)
• Steal personal data or financial information
• Make unauthorized transactions or purchases
• Lock the real user out of their account

Industries Most at Risk of Account Takeover

• Financial Services & Banking: The financial sector continues to be a prime target for attacks due to the potential for direct monetary gains. Attackers exploit banking accounts to conduct unauthorized wire transfers, manipulate payment processes, and engage in cryptocurrency theft.
• E-commerce & Retail: Fraudsters capitalize on e-commerce platforms to exploit stored payment methods, abuse gift cards, and execute fraudulent purchases. The accessibility of customer accounts with saved payment details makes this sector particularly vulnerable.
• SaaS & Cloud Services: Attackers seek access to SaaS and cloud environments to exploit stored data, gain administrative control, and leverage API credentials for further attacks. These platforms often house valuable corporate and customer data, making them attractive targets.
• Healthcare & Government: Medical identity theft, fraudulent insurance claims, and exploitation of government benefits remain significant threats. The increasing digitization of healthcare and public services has expanded the attack surface, with stolen medical records fetching high prices on the dark web.

Account Takeover Statistics 2025

• 71% year-over-year increase in cyberattacks using stolen or compromised credentials. (IBM, 2024)
• Traditional identity fraud losses accounted in nearly $23 billion in 2023, and account takeover fraud resulted in nearly $13 billion. (Javelin Strategy & Research, 2024)
• In 2023 alone, account takeover fraud resulted in nearly $13 billion in losses, up from $11 billion in 2022. (Sift, 2024)
• Password reuse is one of the leading reasons Account Takeover can cause so much collateral damage, with 78% of individuals using the same password for more than one account. (Sift, 2024)
• 73% of consumers believe the brand is accountable for ATO attacks and responsible for protecting account credentials. (Sift’s, 2023)
• In 2024, 80% would not continue shopping on a site where they had been a victim of account takeover, up from 76% in 2023. (Sift, 2024)

Why ATO is More Dangerous Than You Think

Why do Fraudsters Take Over Accounts

Account Takeover is no longer just about stolen funds or compromised accounts. Attackers are using it to conduct corporate espionage, launch ransomware attacks, and manipulate digital identities for fraud.

Once an attacker gains control of an account, they can pivot within an organization, escalate privileges, and exfiltrate sensitive data. Many ATO are part of larger business email compromise (BEC) campaigns, where attackers infiltrate corporate emails to conduct fraudulent transactions.

Impact of Account Takeover

The financial impact can be devastating, with businesses suffering direct monetary losses, regulatory fines, and increased fraud mitigation costs. The reputational consequences are equally concerning, as customers lose trust in affected organizations, leading to decreased user engagement and revenue loss.

In addition to financial and reputational damage, they can also disrupt business continuity. Organizations may face operational delays, legal repercussions, and the need to implement emergency recovery protocols. The longer the attack goes undetected, the greater the impact on the organization’s ability to maintain smooth operations, serve customers, and protect its brand.

How Does Account Takeover Happen? (The Full List of Attack Techniques)

Credential Stuffing Attacks

Attackers use databases of leaked username-password combinations to access accounts. They rely on users reusing credentials across multiple sites, making credential stuffing attacks a widespread and automated method. Also known as a breach replay attack, this technique allows cybercriminals to infiltrate multiple accounts with minimal effort. Regulatory bodies like the CNIL emphasize the risks and recommend unique passwords and strong MFA to mitigate threats.

Credential Cracking Attacks

Credential cracking is a broad term that refers to any method attackers use to systematically guess or recover passwords. Unlike credential stuffing, which relies on previously leaked credentials, credential cracking attempts to “break” a password using various techniques, often exploiting weak or predictable password choices. Common types of credential cracking attacks:

• Brute Force Attacks – Attackers systematically try every possible password combination until they find the correct one. This method is resource-intensive but effective against weak or short passwords.
• Dictionary Attacks – Instead of trying every possible combination, attackers use a precompiled list of commonly used passwords and variations to increase efficiency.
• Hybrid Attacks – A combination of brute force and dictionary attacks, where attackers take a base dictionary password (e.g., “password”) and modify it by adding numbers or special characters (e.g., “Password123!”).
• Credential Spraying – Instead of targeting a single user with multiple password attempts, attackers test a few common passwords (e.g., “123456”, “password”, “qwerty”) across many accounts to avoid triggering lockout mechanisms.

Phishing Attacks

Phishing attacks trick users into providing login credentials via fake emails, websites, or messages. Email phishing attacks remain a primary method, but with AI-generated phishing scams, attackers are now creating hyper-realistic fake messages. Businesses need MFA phishing resistant like TrustBuilder MFA or FIDO2 to mitigate these attacks.

Social Engineering (SIM Swaps, Fake IT Support)

Social engineering manipulate victims into revealing sensitive information or granting account access through psychological deception. A common tactic is SIM swapping, where attackers trick mobile carriers into transferring a victim’s phone number to a new SIM card, allowing them to intercept SMS-based MFA codes. Another method is fake IT support scams, in which attackers impersonate IT personnel or customer service agents to deceive users into providing login credentials or resetting their passwords.

Pass-the-PRT (Azure Token Theft)

Pass-the-PRT (Primary Refresh Token) target Microsoft Azure environments, where attackers steal refresh tokens from compromised devices. Since PRTs allow persistent access without requiring users to re-enter credentials, attackers can move laterally across an organization’s cloud infrastructure undetected. This type of attack is particularly dangerous because revoking passwords or MFA alone does not necessarily invalidate an attacker’s access if they have a valid PRT.

Cookie Poisoning

Cookie poisoning occurs when attackers manipulate authentication cookies stored in a user’s browser to gain unauthorized access to web applications. By altering session cookies, attackers can escalate privileges, hijack sessions, or maintain persistent access to accounts without requiring login credentials. This attack is particularly effective in environments where session expiration policies are weak or where cookies are not adequately encrypted.

Man-in-the-Middle (MITM) & Adversary-in-the-Middle (AITM) Attacks

Man-in-the-middle attacks (MITM) occur when attackers intercept communication between users and legitimate services to steal credentials, session tokens, or other authentication data. This is especially effective on unsecured networks or improperly configured encryption. Attackers can use rogue Wi-Fi hotspots, compromised routers, or DNS spoofing to redirect users to malicious websites or intercept login credentials in transit.

Adversary-in-the-Middle (AITM) are an advanced form of MITM, designed to bypass traditional MFA by intercepting authentication tokens in real time using phishing proxies like EvilProxy, Evilginx, and Modlishka. However, phishing resistant MFA methods significantly reduce the risk of account takeover attempts through these tactics.

Read more on MITM and AITM attacks.

Malware Attacks

A Malware attack involve using malicious software to steal credentials, intercept authentication tokens, or exfiltrate sensitive data. Examples include:

• Keyloggers: Record keystrokes to capture usernames, passwords, and authentication codes.
• Infostealers: Extract stored credentials from browsers, password managers, and applications.
• Remote Access Trojans (RATs): Allow attackers to take full control of an infected device, enabling them to bypass authentication and manipulate user sessions.
• Banking Trojans: Specifically designed to steal credentials for financial institutions, often using web injection techniques.

The Rise of AI and Automated Attacks

AI-powered attacks have transformed Account Takeover techniques, making fraud more scalable, realistic, and harder to detect. Generative AI enables attackers to create highly convincing phishing emails, scam messages, and fake login pages that are nearly indistinguishable from legitimate communication. 

Beyond email, deepfake technology is being used for social engineering scams. Attackers can now generate fake voices and video calls that impersonate executives, customer service representatives, or IT support. AI is also being leveraged to evade CAPTCHA, bypass fraud detection systems, and conduct large-scale automated credential stuffing.

As AI-generated fraud grows, businesses must adopt behavioral biometrics, adaptive authentication, and AI-driven threat detection to defend against these evolving threats.

How Attackers Scale Attacks

Botnets & Automated ATO Tools

Botnets are networks of infected devices controlled by attackers to carry out large-scale account takeover attacks. These compromised devices automate credential stuffing, brute force attacks, and phishing campaigns, making them faster and harder to detect.

Attackers use automated tools with botnets to:

• Test stolen credentials at scale while avoiding IP-based security measures.
• Automate brute force by distributing login attempts across many devices.
• Bypass CAPTCHA and fraud detection using AI-driven bots that mimic human behavior.
• Spread phishing through mass emails and fake login pages.

Because botnets operate from thousands of IPs, traditional security defenses struggle to detect them.

Exploiting Web & API Vulnerabilities

Attackers often target insecure APIs and web applications vulnerabilities to bypass login and take over accounts. Weak API security, exposed tokens, and misconfigured access controls allow attackers to bypass login protections without relying on stolen credentials. Poorly secured APIs also enable mass automated attacks, making them a prime target for cybercriminals.

Exploiting Traditional 2FA Vulnerabilities

Attackers exploit weaknesses in traditional 2FA to bypass security controls. MFA fatigue attacks bombard users with repeated authentication requests until they mistakenly approve one. SIM swapping allows attackers to hijack SMS-based MFA codes by transferring a victim’s phone number to a new SIM card. MITM intercept authentication tokens, enabling access without needing passwords. As these techniques evolve, relying solely on traditional MFA is no longer enough—stronger, phishing resistant authentication methods are essential.

How to Prevent Account Takeover

Integrate ATO Mitigation into Identity Threat Detection & Response (ITDR)

Rather than treating ATO prevention as an isolated issue, organizations should embed it within a holistic identity security strategy, including:

• Zero Trust: Continuously verify user identities throughout the session, not just at login.
• Session Monitoring: Analyze post-login behavior to detect anomalies in real-time.
• AI-Driven Risk Assessment: Leverage machine learning to identify high-risk activities and dynamically enforce step-up authentication.

As highlighted by Gartner, “ITDR offers a second and third layer of defense beyond the foundational controls such as privileged access management (PAM) and identity governance and administration (IGA). It provides preventive controls to limit the exposure of excessive privileges if a credential is compromised. Detecting and preventing ATOs thus becomes a critical component of an ITDR strategy designed to prevent attacks on the IAM infrastructure.”

Moving Beyond Passwords & Traditional MFA

Passwords alone are no longer sufficient, and traditional MFA is becoming vulnerable to social engineering and fatigue attacks. Organizations should transition to phishing resistant authentication methods and certificate-based authentication.

Implementing Zero Trust Architecture ensures continuous verification of user identity rather than relying on one-time authentication at login. Additionally, session risk monitoring and adaptive authentication help prevent unauthorized access by dynamically adjusting security requirements based on risk levels.

Leveraging AI and Automation for Account Takeover Prevention

AI is not just increasing the sophistication of cyberattacks—it’s also a powerful tool for preventing them. Security AI and automation help organizations detect and respond to attempts in real time, significantly reducing risks and financial losses.

AI-driven security systems analyze login behavior, detect anomalies, and flag suspicious activity before attackers can take control of an account. Automation enhances security by enforcing adaptive security, blocking credential stuffing attempts, and mitigating fraud automatically.

Key takeaways

• Credential stuffing and phishing are among the most common methods.
• Attacks have significant consequences, including reputation damage and financial losses.
• Passwords and 2FA are no longer enough to prevent from breaches.
• ATO mitigation part of a broader identity threat detection and response (ITDR) stategy.
• Adaptive, risk-based security is essential to counter evolving threats.