A security researcher used intitle:index.of wallet.dat to find that a small exchange had left their hot wallet exposed. They reported it responsibly and earned a bug bounty.
Indexing can leak metadata: which addresses are used, frequency, and timing. Mitigation strategies: indexofwalletdat+better
If someone obtains your wallet.dat file and it is not encrypted with a strong password, they effectively own your funds. Even if it is encrypted, they can use offline brute-force tools to try and crack your password without you ever knowing. The Anatomy of the "Index Of" Search A security researcher used intitle:index
Accessing a wallet.dat file that does not belong to you is illegal in most jurisdictions and unethical. This guide uses indexof strictly for: indexofwalletdat+better