Self-modifying code: Difference between revisions

Revision as of 10:39, 5 September 2023

Revision as of 10:41, 5 September 2023

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===Use as camouflage===

Self-modifying code is more complex to analyze than standard code and can therefore be used as a protection against [[reverse engineering]] and [[software cracking]]. Self-modifying code was used to hide copy protection instructions in 1980s disk-based programs for platforms such as [[IBM Personal Computer|IBM PC]] and [[Apple II series|Apple II]]. For example, on an IBM PC (or [[IBM PC compatible|compatible]]), the [[floppy disk]] drive access instruction <code>[[int 0x13]]</code> would not appear in the executable program's image but it would be written into the executable's memory image after the program started executing.

Self-modifying code is also sometimes used by programs that do not want to reveal their presence, such as [[computer virus]]es and some [[shellcode]]s. Viruses and shellcodes that use self-modifying code mostly do this in combination with [[polymorphic code]]. Modifying a piece of running code is also used in certain attacks, such as [[buffer overflow]]s.

===Self-referential machine learning systems===

Traditional [[machine learning]] systems have a fixed, pre-programmed learning [[algorithm]] to adjust their [[parameterParameter (computer programming)|parameters]]s. However, since the 1980s [[Jürgen Schmidhuber]] has published several self-modifying systems with the ability to change their own learning algorithm. They avoid the danger of catastrophic self-rewrites by making sure that self-modifications will survive only if they are useful according to a user-given [[fitness function|fitness]], [[error function|error]] or [[reward function|reward]] function.<ref name="Schmidhuber"/>

===Operating systems===