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Execute Disable Bit

Execute Disable Bit

(also EDB, XDB)

Execute Disable Bit definition

Execute Disable Bit is a proprietary no-execute (NX) bit technology found in Intel CPUs. Like other NX bits, Execute Disable Bit is a hardware-based security solution against certain cyberattacks that exploit vulnerabilities in software apps (such as buffer overflow attacks).

While Execute Disable Bit is a proprietary term owned by Intel, similar hardware security features are found in nearly all modern devices. Other hardware systems have their own names for NX bit technology, such as XI (“Execute Inhibit”) bit in MIPS architecture, XN (“Execute Never”) bit in ARM architecture, and the original NX bit in AMD processors.

See also: buffer overflow attack, ARM processor, random access memory, read-only memory, memory allocation

How Execute Disable Bit works

Execute Disable Bit is implemented at the hardware level within the computer’s Intel CPU. The computer’s operating system designates an area in memory as non-executable, allowing the CPU to distinguish which memory areas can be used for program instructions and which should be left untouched (for example, because they hold data or processor instructions).

When an application attempts to execute code in the non-executable memory region, the CPU immediately generates a hardware exception or trap to stop it. Doing so keeps the memory protected, even if the instructions were injected there using a buffer overflow or similar exploit.

Further reading

Ultimate digital security

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