29 Jun
2006
29 Jun
'06
10 p.m.
> Lots of clever ideas to prevent/discourage that
sort of thing ;-)
I knew a fellow who liked to "brand" his code by executing his name.
Actually, it's pretty easy on x86 platforms; most uppercase alphas are
simple 1-byte register ops. For example, "DERMOUSE" would translate to:
INC SP
INC BP
PUSH DX
DEC BP
DEC DI
PUSH BP
PUSH BX
INC BP
The simple way to code this would be to follow this with a bit of "fixup"
code:
DEC BP
ADD SP,5
INC DI
But code of a bit more devious bent would actually set registers up with
known values before the name and then check their values to make sure that
the "name" code has been executed.
I once remember hacking some game that did just this. Drove me nuts when
the execution path veered off into what I thought was data.
Cheers,
Chuck