Alphanumeric shellcode: Difference between revisions
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#REDIRECT [[Shellcode#Alphanumeric]] |
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In [[computer security]] '''alphanumeric shellcode''' is a [[shellcode]] that consists of or assembles itself on execution into entirely alphanumeric [[ASCII]] or [[Unicode]] characters such as 0-9, A-Z and a-z.<ref>{{cite web |last=SkyLined |url=http://www.phrack.org/issues.html?issue=57&id=15#article | title=Writing ia32 alphanumeric shellcodes |publisher=rix }}</ref><ref>{{cite web |last=SkyLined |url=http://www.phrack.org/issues.html?issue=61&id=11#article |title=Building IA32 'Unicode-Proof' shellcodes |publisher=obscou}}</ref> This type of encoding was created by [[Hacker (computer security)|hackers]] to hide working machine code inside what appears to be text. This can be useful to avoid detection of the code and to allow the code to pass through filters that scrub non-alphanumeric characters from strings (in part, such filters were a response to non-alphanumeric [[shellcode]] exploits). A similar type of encoding is called printable code and uses all [[Control character|printable]] characters (0-9, A-Z, a-z, !@#%^&*() etc...) It has been shown that it is possible to create shellcode that looks like normal text in English.<ref>{{cite web|url=http://www.cs.jhu.edu/~sam/ccs243-mason.pdf |last=J. Mason, S. Small, F. Monrose and G. MacManus |title=English shellcode |date=November 2009 |accessdate=2010-01-10}}</ref> |
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Writing alphanumeric or printable code requires good understanding of the [[instruction set architecture]] of the machine(s) on which the code is to be executed. It has been demonstrated that it is possible to write alphanumeric code that is executable on more than one machine.<ref>{{cite web |url=http://www.blackhatlibrary.net/Alphanumeric_shellcode | title=Multi-architecture (x86) and 64-bit alphanumeric shellcode explained |publisher=Blackhat Academy }}</ref> |
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==See also== |
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*[[EICAR test file]] - a test pattern used to test the installation of the anti virus software, which is written in printable code. |
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==Further reading== |
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* [http://www.phrack.org/issues.html?issue=57&id=15#article Writing ia32 alphanumeric shellcodes], an article on how to write alphanumeric shellcode. |
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* [http://www.phrack.org/issues.html?issue=61&id=11#article Building IA32 'Unicode-Proof' shellcodes], an article on how to write Unicode proof shellcode. |
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* [http://skypher.com/wiki/index.php?title=Www.edup.tudelft.nl/~bjwever/whitepaper_shellcode.html.php Writing IA32 restricted instruction set shellcodes], an article on how to write code that is very limited in the number of characters it can use (such as alphanumeric code). |
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* [http://code.google.com/p/alpha3/ ALPHA3], an alphanumeric shellcode encoder: Utility to encode normal machine code into alphanumeric (upper-case or mixed-case) ASCII or Unicode text. |
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* [http://skypher.com/wiki/index.php?title=X86_alphanumeric_opcodes List of x86 Alphanumeric opcodes] |
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* [http://skypher.com/wiki/index.php?title=X64_alphanumeric_opcodes List of x64 alphanumeric opcodes] |
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* [http://www.vividmachines.com/shellcode/shellcode.html#ps Shellcoding for Linux and Windows — Printable Shellcode]: Explanation and tutorial |
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== References == |
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{{reflist}} |
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{{DEFAULTSORT:Alphanumeric Code}} |
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[[Category:Computer security exploits]] |
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[[Category:Injection exploits]] |
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[[Category:Steganography]] |
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[[ca:Alfanumèric]] |
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Latest revision as of 15:43, 10 January 2022
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