Screws used for deck - how to replace?
Chances are you only need to replace the screws that mount the hanger to the ledger. The screws that go diagonally through the joists aren't in shear and should be fine. 

I'd think that no-shear screws of the same size (#8?) as the original screws would do, and hanger nails are typically only 1-1/2" long anyway, so that they penetrate the joist that they're hanging from. Here is Simpson Strong-tie's offering.