Organizations of all types and sizes increasingly rely on Software-as-a-Service (SaaS) platforms, aka “The Cloud” for everything from customer interactions to financial transactions. As organizations outsource functionality that was previously managed internally, account takeover (ATO) attacks are a rising and serious threat. An ATO attack can disrupt operations, leak data, and lead to significant financial losses. In fact, Javelin Strategy & Research (2024-2025) and AARP/Javelin (2025) peg global ATO attack losses at around $13 billion in 2023, rising to $15.6 billion in 2024. And the FBI’s 2024 Internet Crime Report found that Business Email Compromise (BEC) attacks, often enabled through account take over attacks, cost nearly $3 billion. In this article, we will explore what ATO attacks are, the risks they pose to businesses, and practical steps to prevent them.

What Is an Account Takeover Attack?

An ATO attack occurs when a cybercriminal gains unauthorized access to a legitimate user’s account. While employees’ corporate email accounts are often targeted, it could be an account for any application. Unlike data breaches that steal information en masse, ATO attacks are often targeted and stealthy. Once an attacker gains access, they can impersonate the legitimate account owner and use it with their full privileges. ATO attacks typically unfold in stages:

• Credential Acquisition: Attackers obtain credentials (username and password) through methods like phishing (tricking users into revealing passwords via fake emails, texts, or websites), credential stuffing (using passwords stolen from a breach), or malware that logs keystrokes.
• Access and Exploitation: Once in, the attacker might change passwords and enable two-factor authentication (2FA) to lock the legitimate account owner out. More likely though, they will quietly monitor activity to gather sensitive data and learn how to get to money.
• Malicious Actions: The endgame varies but can include fraudulent transactions, intellectual property theft, or launching further attacks from the compromised account.

Driven by AI tools and infostealer malware, ATO attacks surged 24% year-over-year in 2024 and 389% in 2025, per eSentire. AI helps attackers craft very convincing phishing emails and texts, and can even clone a voice, and the rise of remote work expands the attack surface through increasing reliance on personal devices and unsecured networks.

The Risks to Businesses

The consequences of an ATO attack extend far beyond a single compromised account. For businesses, the fallout can be multifaceted and severe:

• Financial Loss: Direct costs include fraudulent purchases, fraudulent invoices, or wire transfers. Indirectly, an attacker in an employee’s account could use the position and authority of the legitimate user to perpetrate fraud. Additionally, if the attack escalates to ransomware or data exfiltration, the business could face extortion demands.
• Operational Disruptions: An attacker could alter critical data, delete files, or even sabotage systems. In supply chain-dependent industries, this might halt production or delay shipments, leading to lost revenue.
• Compliance and Legal Issues: Many industry sectors, including finance and healthcare, are bound by strict regulations. Compromised organizations could face regulatory fines or legal liabilities from affected customers. Additionally, an ATO could lead to non-compliance with contracts triggering audits, penalties, or lawsuits.
• Reputational Damage: When customers become aware of an attack, trust erodes quickly.
• Broader Ecosystem Risks: Compromised accounts can serve as entry points for larger breaches, affecting partners, vendors, or entire networks.

ATOs don’t just steal access, they exploit the interconnected trust that underpins modern business operations and can lead to catastrophic and possibly existential consequences for your organization.

Preventing Account Takeover Attacks

Prevention requires a multi-layered approach, combining technology, policy, employee training, and ongoing vigilance. Here is a roadmap for business leaders:

1. Implement Strong Authentication Measures:
   • Require the use of strong, unique passwords for all organizational accounts. Ban password reuse across personal and work accounts.
   • Use a password manager that facilitates the creation and management of strong unique passwords.
   • Use Passkeys rather than passwords where supported.
   • Enforce phish-resistant multi-factor authentication (MFA) across all accounts. Go beyond SMS-based MFA, which can be intercepted; opt for app-based MFA or hardware tokens.
   • For Microsoft 365 environments, use Microsoft Intune and Conditional Access policies to enforce device compliance, MFA, and risk-based access controls.
2. Monitor and Detect Anomalous Logins:
   • Deploy advanced monitoring tools that flag and alert on unusual login attempts, such as from new devices or unfamiliar locations.
   • Leverage AI-driven behavioral analytics to detect patterns like sudden changes in user activity.
3. Educate Your Team:
   • Conduct regular phishing simulations and cybersecurity awareness training. Empower employees to recognize red flags, like urgent requests for credentials.
   • Create a security culture and reward positive behavior.
   • Perform phish testing on a regular basis.
   • Foster a “zero-trust” culture where access is verified continuously, not just at login.
   • Stay informed through industry resources like the Cybersecurity and Infrastructure Security Agency (CISA) guidelines of the Center for Internet Security Critical Controls.
4. Secure Your Infrastructure:
   • Regularly update software and patch vulnerabilities to prevent exploitation.
   • Apply least‑privilege access principles so that compromised accounts have minimal impact.
   • Lock accounts after a small number of invalid logins.
   • Use web application firewalls (WAFs) and rate-limiting to thwart automated attacks like credential stuffing.
   • Regularly audit third‑party app permissions and revoke unused or risky integrations.
5. Prepare an Incident Response Plan (IRP):
   • Have a clear protocol for responding to suspected ATOs, including immediate account lockdowns and notifications to affected parties.
   • Conduct periodic audits and penetration testing to find weak spots before attackers do.

Investing in these security measures protects your organization. Start with a risk assessment to prioritize high-value accounts, such as executives and those with administrative privileges.

Conclusion

Account takeover attacks are a clear and present danger in our hyper-connected world, but they are not inevitable. By understanding how ATOs work and the havoc they can wreak, organizations can and must take proactive steps to fortify their defenses and protect their accounts. Cybersecurity is a shared responsibility, from the C-suite to frontline staff, everyone plays an increasingly vital role. With the right controls, culture, and vigilance, organizations can dramatically reduce the risk of ATO attacks.

Dave Hatter is an award-winning technology leader with over 30 years of software engineering and cybersecurity experience and is an employee owner and Cybersecurity Consultant at Intrust IT.

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