Source code viruses are a subset of computer viruses that make modifications to source code located on an infected machine. A source file can be overwritten such that it includes a call to some malicious code. By targeting a generic programming language, such as C, source code viruses can be very portable. Source code viruses are rare, partly due to the difficulty of parsing source code programmatically, but have been reported to exist.
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Source code virus Wikipedia(Text) CC BY-SA