Firewalls are easy to misconfigure, but the accumulated risks of misconfigured firewalls in a defense-in-depth OT network architecture are generally unacceptable. This article explores eight common mistakes that firewall administrators make and describes how these mistakes can compromise firewall functionality and network security. Unidirectional gateways provide physical protection for industrial operations, rather than merely software protection. This means no mistake in configuration can impair the protection that the gateway provides to the industrial network. The secret to secure operations is to design our industrial networks so that even when we make mistakes configuring our defenses, there is still no threat to correct and continuous industrial operations.
Source: https://threatpost.com/waterfall-eight-common-ot-industrial-firewall-mistakes/155061/