Password reuse is the practice of using the same password for multiple accounts or services. Password reuse is a bad security habit that can lead to compromise of multiple accounts if one of them is breached by an attacker. Joe has most likely performed password reuse if he thinks his email and banking accounts are also compromised after his password for a social media site was compromised. Joe should use different passwords for different accounts and change them regularly to prevent password reuse. References : The Official CompTIA IT Fundamentals (ITF+) Study Guide (FC0-U61), page 208.