but it only used x86 instructions that were also ASCII characters
That was a somewhat common approach back then. It's hard to find references to that technique now, but here's something I did find: https://news.ycombinator.com/item?id=16312562
That was a somewhat common approach back then. It's hard to find references to that technique now, but here's something I did find: https://news.ycombinator.com/item?id=16312562
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.
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.
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.
(Presumably 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.
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.