The virus can be described in pseudo code[1] The 01234567 is the virus signature, and is used to make sure (if first-line-of-file = 01234567) the file is not already infected.
The virus then asks for permission (ask-permission) to infect a random executable (get-random-executable-file).
If the permission is granted, it compresses the executable (infect-executable), prepends itself to it (prepend), uncompresses the current executable file (uncompress the-rest-of-this-file) into a temporary file (tmpfile) and runs it (run tmpfile).
Cruncher is an example of a compression virus,[2] a strain of which – Cruncher.2092[3] – is described by McAfee as memory-resident virus that infects all but small com files, making them smaller.
The reason for excluding small programs is that their infected versions will be bigger than their originals.