1. Data that is written to be interpreted and takes over
program flow when triggered by some un-obvious operation, such
as viewing it. One use of such hacks is to break security.
For example, some smart terminals have commands that allow one
to download strings to program keys; this can be used to write
live data that, when listed to the terminal, infects it with a
security-breaking
virus that is triggered the next time a
hapless user strikes that key. For another, there are some
well-known bugs in
vi that allow certain texts to send
arbitrary commands back to the machine when they are simply
viewed.
2. In
C, data that includes pointers to functions
(executable code).
3. An object, such as a
trampoline, that is constructed on
the fly by a program and intended to be executed as code.
4. Actual real-world data, as opposed to "test data". For
example, "I think I have the record deletion module finished."
"Have you tried it out on live data?" This usage usually
carries the connotation that live data is more fragile and
must not be corrupted, or bad things will happen. So a more
appropriate response to the above claim might be: "Well, make
sure it works perfectly before we throw live data at it." The
implication here is that record deletion is something pretty
significant, and a haywire record-deletion module running amok
on live data would probably cause great harm.