With only normal privileges, Anthrax couldn't force the load-module
program to run his backdoor Trojan program. But he could trick it into
doing so. The secret was in one simple keyboard character: /.
Unix-based computer systems are a bit like the protocols of the
diplomatic corps; the smallest variation can change something's
meaning entirely. Hackers, too, understand the implications of subtle
changes.
A Unix-based system reads the phrase:
/bin/program
very differently from:
bin program
One simple character--the `/'--makes an enormous difference. A Unix
computer reads the `/' as a road sign. The first phrase tells the
computer, `Follow the road to the house of the user called "bin" and
when you get there, go inside and fetch the file called "program" and
run it'. A blank space, however, tells the computer something quite
different. In this case, Anthrax knew it told the computer to execute
the command which proceeded the space. That second phrase told the
machine, `Look everywhere for a program called "bin" and run it'.
Anthrax prepared for his attack on the load-module program by
installing his own special program, named `bin', into a temporary
storage area on System X.
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