Greg's checklist for securing new Linux-based devices includes disabling unneeded ports and protocols. What primary purpose does this serve?

Disabling unnecessary ports and protocols reduced a device or system's attack footprint. The fewer targets attackers have, the less likely they are to be successful at finding a viable target. Reducing ports and protocols will speed up port scans and will reduce the number of logged events, but this is not the primary purpose of the change. Default ports are set for services based on common practice, and ports and protocols are not disabled to save default ports.