It did contain a USB device exploit delivering a dropper with a completely separate payload specifically targeted at the Natanz facility. A compromised USB device picked up in the parking lot would do the trick, but there are certainly other ways to get something through the front door and that information is unlikely to be public knowledge any time soon.

I do remember reading about that. It exploited a bug in windows to load an executable when the usb was plugged in. It then installed a usermode rootkit and hid its files.

I likely got the "parking lot" impression from Alex Gibney's Zero Days, but it's been a few years since that came out.

It probably got in via usb in the parking lot, but there hasn't been an official statement that I know of. It was confirmed that the hack into the DHS intranet was done by USB stick in the parking lot.