What is necessary for a security interest to be considered "perfected"?

For a security interest to be considered "perfected," it must indeed be attached and proper notice given to third parties. This means that the security interest has acquired the requisite legal status to be enforceable against third parties who may have an interest in the same collateral.

Perfection serves to give notice to other parties (like creditors) that a secured party has an interest in certain collateral, thus providing priority over other claims to that collateral. The attachment of a security interest is the first step, which happens when there is a valid security agreement, value is given, and the debtor has rights in the collateral. However, without the act of perfection—typically achieved through filing a financing statement or giving possession of the collateral—the security interest is not enforceable against third parties who might claim an interest in that same collateral.

Thus, option B correctly encapsulates both essential requirements for perfection in secured transactions: the need for the security interest to be attached and for third parties to be made aware of that interest.