This article and this search suggest that the 32-bit word 0x41414141 is associated to security exploits.

Why is 0x41414141 associated to security exploits?


It's nothing fundamental. It's just a historical convention, like using foo as the name of a variable when you have no clue what to name it.

In more detail: The simplest way to test for a buffer overflow is to type a long string of A's (AAAAAAAA...) into a text field, and see what happens. If the program crashes, it might be vulnerable. If the program crashes and a debugger shows 0x41414141 in the program counter, ooh boy, you hit pay dirt: the program is almost surely vulnerable. (Remember, the ASCII code for 'A' is 0x41 in hex, so 0x41414141 is what you'd see if you looked at the byte-level representation of a string of A's in a hex editor.)

Why A's? No reason at all; they're just the first letter in the alphabet.

So, this is a quick-and-dirty test that pentesters sometimes use. But of course, there's nothing special about 0x41414141. Douglas Adams fans could type in a long string of B's, and then look for 0x42424242. That'd be equally effective, and even more fun. I gotta remember to use that one in my next hacking demo.....

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    I always thought it came from Aleph One's seminal paper 'Smashing the Stack for Fun and Profit' or at least was made popular by it. – lynks Aug 15 '12 at 10:48
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    Some researchers use A's due the the matter that it is easy to count. 41 -> 1 -> A, 42 -> 2 -> B etc etc. – Stolas Sep 30 '13 at 9:54

It's more associated with simple proof of concepts. 0x41414141 is usually the result when a (usually long) string of A's is used to demonstrate an overflow (or something similar).

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