I thought passphrase and seedphrase were the same thing... Thanks for the correction. I've learned something today already
A passphrase is basically a "seed extension" that increases the safety of your assets, it is an added word to your seed phrase that creates an entirely new wallet for you that can only be accessed with both the seed phrase and the passphrase.
How can I detect those apps that carries malware and phishing stuff that will be able to steal my seedphrase.
The only way to be sure of the safety of your assets is to hodl them offline, and not in the device that you connect to the internet with. Your internet connected device should not hodl any of your wallets, and even if it does, it should be a wallet that contains a small amount of coins.