There's also this compiler (with accompanying paper/video), that compiles C89 to x86 with the output executable restricted even further, to only printable ASCII bytes: http://tom7.org/abc/

Another common one is the EICAR anti-virus test file.

X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*

It is a com executable that prints EICAR-STANDARD-ANTIVIRUS-TEST-FILE! It recognized by most virus scanners.

Oh, cool! I thought this file was just prefixed with some random garbage.

Unrelated: I used this to verify that my daily scheduled full scan of my Linux laptop works. This is required by compliance at $WORK. It reports found viruses via the i3-nagbar.

Linux has antivirus software written for it? TIL.

ClamAV is the best known.

Usually, linux antivirus software is not designed to protect the machine itself, instead it is more commonly used by mail and file servers to protect windows clients.

Cool. How many viruses has it picked up?

(Presumably ClamAV?)

Yes, used ClamAV.

None besides this example file.

I use this laptop for $WORK and web browsing, and my warez times are behind me now that the software I want to run is typically open source, and the content I consume can be bought.

This is still quite useful when working on constrained shellcode, specifically the kind of shellcode you'd enter through a text input field.

You can even do one better, you can construct shellcode out of valid english sentences.

http://www.cs.jhu.edu/~sam/ccs243-mason.pdf

Since COM files are basically just raw binary code without headers or metadata, it should be easy to adapt the technique to make valid english language COM files.