There are two main types of IT asset discovery tools: active and passive. Let's start with the first. Active asset discovery tools scan an organization's network actively and periodically to identify connected devices and applications by sending packets of information to devices on the network and recording their responses.
On the other hand, passive asset discovery tools monitor network traffic and collect information about devices and applications without sending any packets. They do not actively scan the network or send out probing requests. Instead, they analyze network traffic and observe device behavior to gather asset information.