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#REDIRECT [[Shellcode#Alphanumeric]]
In general, in [[computing]], an '''alphanumeric code''' is a series of letters and numbers (hence the name) which are written in a form understandable and processable by a computer. One such alphanumeric code is [[ASCII]].
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More specifically, in computer underground terminology alphanumeric code is [[machine code]] that is written so that it assembles into entirely readable ASCII characters such as "a"-"z", "A"-"Z", "1"-"9", "#", "!", "@", and so on.
Writing alphanumeric code requires a good understanding of machine code encoding scheme for the specific architecture that the code is to executed on.
This code is used by [[Cracker (computing)|cracker]]s with the intent of fooling applications, such as Web forms, into accepting code used for [[exploit (computer science)|exploit]]. Typically, such exploits involve [[buffer overflow]]s.
Sometimes, alphanumeric code could also be used when the programmer needs to write a program but does not have access to any [[compiler]] or [[assembly language|assembler]]. All that is needed to write a alphanumeric program is a [[text editor]].
==Example DOS-program==
%!!%BB-tz-!!-%cP\%!!%BB-=<Pu( ------Written by Kalle
The text above will, when interpretended by an [[x86]] [[Central processing unit|CPU]] using the [[DOS]] operating system [[self-modifying code|overwrite parts of itself]] with a code used to terminate the execution of the program, and return back to DOS. Just copy the text into an pure text editor (for example edit.exe in DOS or notepad in Windows), save the file and then rename it to "something.com". To execute the program, just type "something" in a DOS command shell.
[[Category:Security exploits]]
[[ca:Alfanumèric]]
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