An employee has been using the same password for multiple applications and websites for the past several years. Which of the following would be best to prevent security issues?

Configuring firewall settings protects against unauthorized network access and malicious traffic, but it does not address the security risk of a user reusing compromised passwords.

Implementing password expiration policies forces users to change their passwords periodically, which mitigates the risk of a compromised password being used indefinitely across multiple platforms if it were to be discovered or breached.

Defining complexity requirements makes passwords harder to guess or crack through brute force attacks, but it does not prevent users from reusing the same complex password across multiple services or address the risk of long-term credential compromise.

Updating antivirus definitions helps protect against malware and viruses, but it does not directly prevent or mitigate the security risks associated with password reuse across multiple applications and websites.