Firewalls are an essential part of network security, yet Gartner says 95% of all firewall breaches are caused by misconfiguration. In my work I come across many firewall configuration mistakes, most of which are easily avoidable. Here are five simple steps that can help you optimize your settings:
* Set specific policy configurations with minimum privilege. Firewalls are often installed with broad filtering policies, allowing traffic from any source to any destination. This is because the Network Operations team doesn’t know exactly what is needed so start with this broad rule and then work backwards. However, the reality is that, due to time pressures or simply not regarding it as a priority, they never get round to defining the firewall policies, leaving your network in this perpetually exposed state.
You should follow the principle of least privilege – that is, give the minimum level of privilege the user or service needs to function normally, thereby limiting the potential damage caused by a breach. You should also document properly – ideally mapping out the flows that your applications actually require before granting access. It’s also a good idea to regularly revisit your firewall policies to look at application usage trends and identify new applications being used on the network and what connectivity they actually require.
* Only run required services. All too often I find companies running firewall services that they either don’t need or are no longer used, such as dynamic routing, which typically should not be enabled on security devices as best practice, and “rogue” DHCP servers on the network distributing IPs, which can potentially lead to availability issues as a result of IP conflicts. It’s also surprising to see the number of devices that are still managed using unencrypted protocols like Telnet, despite the protocol being over 30 years old.
The solution is to harden devices and ensure that configurations are compliant before devices are promoted into production environments. This is something a lot of organizations struggle with. By configuring your devices based on the function that you actually want them to fulfil and following the principle of least privileged access – before deployment – you will improve security and reduce the chances of accidentally leaving a risky service running on your firewall.
* Standardize authentication mechanisms. During my work, I often find organizations that use routers that don’t follow the enterprise standard for authentication. One example I encountered is a large bank that had all the devices in its primary data centers controlled by a central authentication mechanism, but did not use the same mechanism at its remote office. By not enforcing corporate authentication standards, staff in the remote branch could access local accounts with weak passwords, and had a different limit on login failures before account lockout.
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