In the language of cryptocurrencies, the term dust refers to a tiny amount of coins or tokens – an amount that is so small that most users don’t even notice. Taking Bitcoin as an example, the smallest unit of BTC is 1 satoshi (0.00000001 BTC), so we may use the term dust to refer to a couple of hundreds of satoshis.
A dust attack is send to non-spendable funds as well as confirm and unconfirmed bitcoins. A dust is not a hack nor a private-key but a direct attack on the funds which will be automatically transferred to your wallet. A bitcoin dust does not attack an address leaving a remainder,it sweeps away everything in the wallet and transfer to the beneficiary address.