[open_bear]

IIRC, uranium enrichment centrifuges in Iran were infected by Stuxnet because someone brought an infected USB stick, found in the parking lot, into the facility.

Social engineering is the best way to infiltrate the airgapped infrastructure.

[throwaway7645]

I don't think you should be able to plugin a thumb drive to critical infrastructure. I don't disagree that this happened, but modern well designed systems shouldn't allow it.