It may not even have anything to do with the wallet that the 'hackers' have in their possession. Bitcoin wallets typically have the address section in the clear, with the private keys encrypted behind a strong passphrase.

Some people enjoy taking a wallet with some random (worthless) private keys then edit it and toss in some addresses with massive amounts of bitcoin behind them, then release it to the web and grab some popcorn as people throw ridiculous amounts of compute at the wallet trying to crack it.