Why does a larger block size infer a bigger attack vector I have read this in several articles that larger block sizes makes adversarial attacks easier. What I wonder is why is that so obvious? is it because in a larger block the number of transactions could increase to a number that it becomes hard to validate each one of them?
Usually Denial Of Service(DoS) attack may take place on larger sized blocks.So to avoid this condition initially block size Bitcoin was chosen to be 1Mb. Because attacker sends a lot of data in the network to make it busy so that the actual transactions are not able to take place.
Along with reducing block size other methodology which is adopted in Bitcoin are:


No forwarding of orphaned blocks
No forwarding of double-spend transactions
No forwarding of same block or transactions
Disconnect a peer that sends too many messages
Restrict the block size to 1 MB
Limit the size of each script up to 10000 bytes