1. A secure protection method, executed by a processor, comprising: obtaining, from a plurality of security lookup entries (SLEs), an instruction security attribute (ISA) of a first instruction, an ISA of a second instruction, a security attribute (SA) of an operational event (OE) and a data security attribute (DSA) of an operation resource accessed by the first instruction, wherein the OE is generated as a side effect when the processor fetches or executes the first instruction, generated as a monitoring result on the first instruction, or generated in response to an external input of the processor; performing a first security checking before or after executing the first instruction according to the ISA of the first instruction and the SA of the OE; ignoring the OE, deferring the OE, or raising a security exception when the first security checking fails; performing a second security checking and a third security checking, wherein: the second security checking is to determine whether the ISA of the first instruction is less secure than the DSA of the operation resource by comparing the ISA of the first instruction with the DSA of the operation resource, wherein when the ISA of the first instruction is determined not less secure than the DSA of the operation resource, accessing the operation resource for performing the first instruction, and the third security checking is to determine whether the ISA of the first instruction is less secure than the ISA of the second instruction by comparing the ISA of the first instruction with the ISA of the second instruction, wherein the processor fetches the second instruction immediately after the processor fetches the first instruction; and raising the security exception when any one of the second security checking and the third security checking fails.