Hacking Multifactor Authentication

Multifactor authentication adds layers to a login, but those layers do not exist in isolation. In Hacking Multifactor Authentication, computer security professional Roger A. Grimes examines how MFA works, how attackers can undermine it, and what organizations can do to choose and defend stronger solutions.

Understand the system behind the sign-in

The book first establishes the groundwork: password and logon problems, authentication basics, different authentication methods, and the tension between usability and security. That context helps readers see why MFA is valuable—and why the details of its implementation matter.

Explore the ways MFA can fail

Grimes surveys a broad range of attack approaches, including attacks involving access-control tokens, endpoints, SMS, one-time passwords, biometrics, social engineering, account recovery, physical access, DNS, and APIs. The focus is not only on the authentication factor itself, but on the surrounding processes and connections that can create opportunities for compromise.

Pair attack knowledge with defense

Alongside the vulnerabilities, the book discusses mitigations and the design and selection of more defensible MFA solutions. This perspective makes the material relevant to security practitioners assessing existing systems as well as teams responsible for developing or choosing authentication methods.

Who may find it useful?

Security professionals, penetration testers, and readers involved in identity and access management can use this book to build a more critical understanding of MFA. It connects the mechanics of authentication with practical questions about implementation, recovery, and risk—helpful context when evaluating whether a solution is secure in practice, not just on paper.

For readers responsible for protecting accounts and systems, this is a focused examination of MFA’s strengths, weaknesses, and defenses.