[sandworm101]

I don't see that even a real attack taking out every ATM in Iran would qualify as the largest anything in history. There aren't enough ATMs in the country.

[woodruffw]

The phrasing could be bad, given that it's a (likely) ESL source: they might mean it's one of the largest cyberattacks on Iran in history.

(I don't have a factual opinion on the claim, only that this phrasing interpretation seems possible to me.)