[alias1]

Depending on your needs, you absolutely can do it in software. The first few steps are about software, and in particular, probably just using Wireshark + USBPcap or usbmon is sufficient for basic cases.

The hardware side of things is the area that interests me more though, if you want to get into higher speeds than can be handled in software only, or if you want to start doing weird/interesting things in the 'emulate' side of it (not just capturing (eg. facedancer). Coming from a security perspective, those sorts of tools are invaluable for getting to some of the depths that I may want to reach.