A complete inventory of computer hardware and business data is a critical step to cybersecurity

A complete inventory of computer hardware and business data is a critical step to implementing proper security controls. You can't protect what you don't know you have.

When I notify victim companies of an intrusion, many times they are unfamiliar with the computer on their network that has been compromised.
 
Common responses are that the computer is a forgotten server that hosts an outdated software package or is used for testing. Unfortunately these insecure devices are exposed to the internet and are easily exploited by cyber threat actors. The threat actors then exploit other computers on the network or deploy ransomware. 
 
Keep in mind that smart devices such as thermostats, smart switches, security cameras and digital assistants are also on the network and may be exploited as an entry point to your network.
 
There are many software tools that aid in building an asset inventory, help track devices that are on the network and can notify you if a rogue device shows up. At the least, a simple spreadsheet with information on the hardware, the data it has access to, its function and who is responsible for it should be maintained. Once an asset inventory is established, security controls can be implemented to protect those hardware and data assets.