What is credential reuse and why is it risky?

• A. Using different credentials across services but the same password.
• B. Using the same credentials across multiple services; if one is compromised, others may be breached.
• C. Not reuse credentials across any service.
• D. Using the same credentials across services and changing them frequently.

Answer: (B)

Credential reuse means using the same login credentials across multiple services. This is risky because when one site is breached and those credentials are exposed, attackers can try the same username and password on other sites. If users have reused their credentials widely, this allows a cascade of unauthorized access across many accounts—often through automated credential stuffing.

The best description matches this idea: using the same credentials across several services and recognizing that a breach on one service can lead to breaches on others. The other options don’t capture the full risk: one describes only using the same password with different usernames, which isn’t the same as reusing the exact credentials; another suggests not reusing credentials—which minimizes risk; and another adds frequent changes, which doesn’t define the core vulnerability.