ASLR.

Address Space Layout Randomization randomizes the memory locations of code, stacks, heaps, and libraries so attackers cannot reliably predict target addresses for exploits. It belongs to the Application Security category of cybersecurity.

Address Space Layout Randomization randomizes the memory locations of code, stacks, heaps, and libraries so attackers cannot reliably predict target addresses for exploits.

ASLR is a defensive mitigation that randomizes the base addresses of key process regions — the executable, shared libraries, heap, stack, and mmap area — each time a program runs. It was pioneered by the PaX project in 2001 and has since shipped in Linux, Windows, macOS, iOS, and Android. By making memory layout unpredictable, ASLR forces an attacker to first leak an address before mounting code-reuse attacks such as ROP. Effectiveness depends on entropy (more bits is better), full coverage including PIE/ASLR-enabled binaries, and complementary mitigations like DEP/NX, stack canaries, and CFI to defeat partial-overwrite and info-leak techniques.

Defences for ASLR typically combine technical controls and operational practices, as detailed in the full definition above.

Common alternative names include: Address Space Layout Randomization, PIE.