A firewall is a security guard placed at the point of entry between a private network and the outside Internet such that all incoming and outgoing packets have to pass through it. The function of a firewall is to examine every incoming or outgoing packet and decide whether to accept or discard it. This function is conventionally specified by a sequence of rules, where rules often conflict. To r...

Practically every corporation that is connected to the Internet has at least one firewall, and often many more. However, the protection that these firewalls provide is only as good as the policy they are configured to implement. Therefore, testing, auditing, or reverseengineering existing firewall configurations should be important components of every corporation’s network security practice. Un...

In multi-application Java Cards, applet’s sensitive data must be protected against unauthorized accesses. Applet isolation is normally achieved through the firewall mechanism. The firewall allows an applet to access external objects only through an object sharing mechanism, called shareable interface. Firewall is based on the access control policy and does not control information propagation. T...

For administrators of large systems, testing and debugging a firewall policy is a difficult process. The size and complexity of many firewall policies make manual inspection of the rule set tedious and error-prone. The complex interaction of conflicting rules can conceal serious errors that compromise the security of the network or interrupt the delivery of important services. Most existing too...

Firewall policies can be extremely complex and difficult to maintain, especially on networks with more than a few hundred machines. The difficulty of configuring a firewall properly often leads to serious errors in the firewall configuration or discourage system administrators from implementing restrictive policies. In previous research, we developed a technique for modeling firewall policies u...

Firewalls are the mainstay of enterprise security and the most widely adopted technology for protecting private networks. The quality of protection provided by a firewall directly depends on the quality of its policy (i.e., configuration). Due to the lack of tools for analyzing firewall policies, most firewalls on the Internet have been plagued with policy errors. A firewall policy error either...

Corporate network firewalls are well-understood and are becoming commonplace. These firewalls establish a security perimeter that aims to block (or heavily restrict) both incoming and outgoing network communication. We argue that these firewalls are neither effective nor appropriate for academic or corporate research environments needing to maintain information security while still supporting t...

Firewalls are critical components of network security and have been widely deployed for protecting private networks. A firewall determines whether to accept or discard a packet that passes through it based on its policy. However, most real-life firewalls have been plagued with policy faults, which either allow malicious traffic or block legitimate traffic. Due to the complexity of firewall poli...

Firewalls are one of the most important devices used in network security today. Their primary goal is to provide protections between parties that only wish to communicate over an explicit set of channels, expressed through protocols. These channels are implemented and described in a firewall using a set of rules, collectively referred to as a firewall policy. However, understanding the policy t...