One need only specify some reasonable length either equivalent to infinity for such a program, use a heuristic of checking whether the program is in the same loop and if so, whether any of the variables involved in determining loop termination are changing. Of course, proper security precautions are required.
For any finite number of clock cycles N, in a Turing-complete language, I can write you a program which terminates but takes longer than N cycles. There is therefore no value of N which will consistently give the correct results in your program.
Turing machines have an infinite tape, so under a Turing machine model, there are infinitely many loop termination conditions, and so it is possible to craft a program which never repeats the same state within N cycles for any N but still terminates.
If your machine is finite state (with no inputs) and s possible states, rather than a Turing machine, you can check if the program halts:
halts s program initialState = do
seenState <- newBooleanArrayOfSize s
setBooleanEntry seenState initialState
halts' initialState
where
halts' state0 =
if state0 == HaltingState
then return True
else
do
seenAlready <- getBooleanEntry seenState state0
if seenAlready
then return False
else
state1 <- nextState program state0
setBooleanEntry seenState state1
halts' state1
Of course, the real question anyone asked to develop such a program would be what runtime is equivalent to an infinite loop. Any real-world program must have a runtime bound that is predictable on invocation or it's useless.