In computer security, executable space protection is the marking of memory regions as non-executable, such that an attempt to execute machine code in these regions will cause an exception. It makes use of hardware features such as the NX bit.
The Burroughs 5000 offered hardware support for executable space protection when it was introduced in 1961; that capability was retained in its successors at least through 2006. In its implementation of tagged architecture, each word of memory had an associated, hidden tag bit designating it code or data. Thus, user programs cannot write or even read a program word, and data words cannot be executed.
If an operating system can mark some or all writable regions of memory as non-executable, it may be able to prevent the stack and heap memory areas from being executable. This helps to prevent certain buffer overflow exploits from succeeding, particularly those that inject and execute code, such as the Sasser and Blaster worms. These attacks rely on some part of memory, usually the stack, being both writable and executable; if it is not, the attack fails.
Read more about Executable Space Protection: OS Implementations
Famous quotes containing the words space and/or protection:
“Our passionate preoccupation with the sky, the stars, and a God somewhere in outer space is a homing impulse. We are drawn back to where we came from.”
—Eric Hoffer (1902–1983)
“If one really wishes to know how justice is administered in a country, one does not question the policemen, the lawyers, the judges, or the protected members of the middle class. One goes to the unprotected—those, precisely, who need the laws’s protection most!—and listens to their testimony.”
—James Baldwin (1924–1987)