Definition
Account Takeover (ATO) is the class of attack where an attacker gains unauthorized access to a legitimate user's account — typically via credential stuffing, phishing, SIM swapping, or session hijacking.
In more depth
ATO is the dominant identity threat against consumer + B2B SaaS products. Credential stuffing (testing leaked credentials against many sites) is the most common vector. Akamai recorded 193 billion credential-stuffing attempts in one year. Defenses combine rate limiting, bot mitigation, leaked-credential screening, risk-based MFA, and passkey rollout.
The FFIEC layered-security guidance and EU PSD2 SCA mandate are the main regulatory drivers in financial services. For e-commerce, fraud-loss economics drive investment.
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