An adaptive security apparatus is arranged for updating a security parameter in a database. The adaptive security apparatus includes a message receiver, a data processor, a security processor, and an adaptive parameter processor. The message receiver is arranged for receiving a message. The data processor is arranged for receiving the message from the message receiver and a security parameter from the database. The security processor is arranged for performing a deciphering process and a decoding process according to an output of the data processor. The adaptive parameter processor is arranged for updating the security parameter. Besides, an adaptive security method arranged for adaptively updating a security parameter includes: checking a status of a deciphering process and accordingly generating a checking result; and referring to the checking result to adaptively search a target pattern of the security parameter from a plurality of candidate patterns.