Are you talking about hacks on individual wallets or attacks on the blockchain/devs etc themselves? Anyways, there have been a lot of different hacks, scams and all kinds of other things in the past. We are living in the wild wild west right now.
I also still try to understand which hack does he mean? Hack to wallet or blockchain?
If blockchain i will say it is not hackable. But if wallet hack, there are many issue about it out there since they are not aware to security.
We must put security in first of all amd use 2FA is recommended.