LogFAQs > #961728674

This is the contract address for cryptopunks:

https://etherscan.io/address/0xb47e3cd837ddf8e4c57f05d70ab865de6e193bbb

All legitimate crypto punks were created using this contract and are inexorably linked to that contract. Full stop.

You could right click -> save as a cryptopunk and have a jpeg that looks the same, but you would not be the owner, because the blockchain would not say you were the owner.

You could that jpeg and mint an NFT using out of it, but it would not be on the correct contract so it would not be legitimate. It would just be some other non crypto punk NFT that used the same image.

Edit: And I don't know all the particulars of the banksy situation, but it sounds like banksy has not made any NFTs of his artwork, so bidding on one that is supposedly from him would be pretty suspicious.