A dusting attack is a kind of scam. It deanonymizes a wallet owner in order to target the owner with phishing campaigns or extortion threats.

A dusting attack consists in sending tiny amounts of cryptocurrencies to different wallets. The scammer then tracks these wallets and ultimately identifies the owners behind the targetted wallets.
Once hackers or scammers deanonymized the wallet, they can use the information in phishing attacks targetting the owner.

Often the cryptocurrency amount sent is so small that the wallet owners don't even notice they have been targets of a dusting attack.