Hello NovemberAdam,
Yes, Attack Spells are considered attacks too, and will trigger a Block enchantment.
Attack spells are both a spell and an attack. When you cast them, they are cast just like any spell, with a Casting Step, and a Counter Spell Step. Then, during the Resolve Spell Step, they are resolved just like an attack, following all of the normal Attack Steps. For the Declare Attack Step, most of these choices and checks have already been accomplished during the Cast Spell Step (choose target, checking range and LoS, pay mana costs, etc.). Then, you move right on to the Avoid Attack Step.
Hope this helps!