Usability and Security of Personal Firewalls

Effective security of a personal firewall depends on (1) the rule granularity and the implementation of the rule enforcement and (2) the correctness and granularity of user decisions at the time of an alert. A misconfigured or loosely configured firewall may be more dangerous than no firewall at all because of the user’s false sense of security. This study assesses effective security of 13 personal firewalls by comparing possible granularity of rules as well as the usability of rule set-up and its influence on security. In order to evaluate usability, we have submitted each firewall to use cases that require user decisions and cause rule creation. In order to evaluate the firewalls’ security, we analysed the created rules. In addition, we ran a port scan and replaced a legitimate, network-enabled application with another program to assess the firewalls’ behaviour in misuse cases. We have conducted a cognitive walkthrough paying special attention to user guidance and user decision support. We conclude that a stronger emphasis on user guidance, on conveying the design of the personal firewall application, on the principle of least privilege and on implications of default settings would greatly enhance both usability and security of personal firewalls.