- Obtain copies of relevant security policies.
- Obtain access to firewall logs that can be analyzed against the firewall rule base to understand what is actually being used.
- Obtain a diagram of the current network and firewall topologies
- Obtain reports and documents of previous audits, including firewall rules, objects and policy revisions.
- Identify all Internet Service Providers (ISP) and Virtual Private Networks (VPN)
- Obtain all relevant firewall vendor information including OS version, latest patches and default configuration.
- Understand all the key servers and key information repositories in the network and their relative values to the company.
A good change management process is essential to ensure proper execution and traceability of
firewall changes, as well as sustainability over time to ensure continuous compliance vs. point-intime compliance. Poor documentation of changes, including why the change is needed, who
authorized the change, etc. and poor validation of the impact on the network are two of the most
common issues when it comes to change control.
- Review the procedures for rule-base maintenance. Just a few key questions to review include:
- Are requested changes going through proper approvals?
- Are changes being implemented by authorized personnel? And are they being tested?
- Are the changes being documented per regulatory or internal policy requirements?
Each rule should have a comment that includes the change ID of the request and the
name/initials of the person who implemented the change
- Is there an expiration date for the change?
- Determine if there is a formal and controlled process in place to request, review, approve and
implement firewall changes.
Note: This process should include at least the following:
- Business purpose for the request
- Duration (time period) for the new/modified rule
- Assessment of the potential risks associated with the new/modified rule
- Formal approvals for the new/modified rule
- Assignment to proper administrator for implementation
- Verification that change has been tested and implemented correctly
- Determine whether or not all of the changes been authorized, and flag any unauthorized rule
changes for further investigation.
- Determine if real-time monitoring of changes to the firewall is enabled and access to rule
change notifications is granted to authorized requestors, administrators and stakeholders
- Ensure firewall and management servers are physically secured with controlled access.
- Ensure there is a current list of authorized personnel permitted to access the firewall server rooms.
- Verify that all appropriate vendor patches and updates have been applied.
- Ensure the operating system passes common hardening checklists.
- Review the procedures used for device administration.
- Delete covered rules that are effectively useless.
- Delete or disable expired and unused rules and objects.
- Identify disabled, time inactive and unused rules which are candidates for removal.
- Evaluate the order of firewall rules for effectiveness/performance.
- Remove unused connections, including specific source/destination/service routes that are not in use.
- Detect similar rules that can be consolidated into a single rule.
- Identify overly permissive rules by analyzing the actual policy usage against the firewall logs. Tune these rules as appropriate for policy and actual real use scenarios. For example, “ANY” might be used for the source address in several rules when actual traffic only originates from a handful of IP addresses
- Analyze VPN parameters to identify unused users, unattached users, expired users, users about to expire, unused groups, unattached groups and expired groups.
- Enforce object naming conventions.
- Document rules, objects and policy revisions for future reference.
- Identify any and all potentially “risky” rules, based on industry standards and best practices,
and prioritize them by severity. What is “risky” can be different for each organization
depending on the network and the level of acceptable risk, but there are many frameworks
and standards you can leverage that provide a good reference point. A few things to look for
and validate include:
- Are there firewall rules that violate your corporate security policy?
- Are there any firewall rules with “ANY” in the source, destination, service/protocol, application or user fields, and with a permissive action?
- Are there rules that allow risky services from your DMZ to your internal network?
- Are there rules that allow risky services inbound from the Internet?
- Are there rules that allow risky services outbound to the Internet?
- Are there rules that allow direct traffic from the Internet to the internal network (not the DMZ)?
- Are there any rules that allow traffic from the Internet to sensitive servers, networks, devices or databases?
- Analyze firewall rules and configurations against relevant regulatory and/or industry standards such as PCI-DSS, SOX, ISO 27001, NERC CIP, Basel-II, FISMA and J-SOX, as well as corporate policies that define baseline hardware and software configurations to which devices must adhere. See Figure 4 below.
- Document and assign an action plan for remediation of risks and compliance exceptions found in risk analysis.
- Track and document that remediation efforts are completed.
- Verify that remediation efforts and any rule changes have been completed correctly.
- Ensure a process is established for continuous auditing of firewalls
- Consider replacing error-prone manual tasks with automated analysis and reporting.
- Ensure all audit procedures are properly documented, providing a complete audit trail of all firewall management activities.
- Make sure that solid firewall change workflow is in place to sustain compliance over time.
- Ensure there is an alerting system in place for significant events or activities, such as changes in certain rules or the discovery of a new, high severity risk in the policy.