When opening an account on a cryptocurrency exchange, you will often (though not always) be required to undergo KYC verification. This process requires financial service providers to request information from the customer to verify their identity, such as official documents or bank statements. Just like AML requirements, KYC helps prevent money laundering, terrorist financing, fraud and illegal financial transactions.
KYC helps prevent crime rather than react to it. Most financial services require customer data during the registration process - even before they can make financial transactions. In some cases, accounts can be created without passing KYC, but then their functions will be limited.
KYC is aimed at preventing crime rather than reacting to it. Many services request client data at the registration stage, before transactions begin. In some cases, accounts can be created without KYC, but their functionality will be limited. For example, a ban on trading or restrictions on amounts.