Installation of a(n) is the most common computer security precaution taken by businesses.

The correct answer is Firewall.

Explanation:

A firewall is a system that allows you to protect a computer or a computer network from intrusions that come from a third network (expressly from the Internet). The firewall is a system that allows you to filter the data packets that go through the network. It is a "narrow bridge" that filters at least the traffic between the internal and external network.

A firewall can be a program (software) or a computer (hardware) that acts as an intermediary between the local network (or the local computer) and one or more external networks.