As discussed before, Netrunners move at a speed of five spaces per round. But how fast do programs move, if ever?
Most programs are limited to staying within the confines of a system. However, once they spot you, they can move anywhere within the system to intercept, also moving at a speed of five spaces per round. A program can pursue a Netrunner anywhere within it's home system, and up to one space outside of it. It will then break off the attack and go back to it's original position.
Hellhounds, Bloodhounds and Pit Bulls have no such restrictions; they are designed with a tracing function that allows them to move away from their home system and follow you anywhere. The only way to ditch one of these monsters is to jack out and hope the pursuer isn't able to make a successful Trace roll on you. Otherwise, it'll be waiting the next time you log on in that location of the Net.
Trace Rolls: A Trace roll is made by comparing the program's STRENGTH + 1D10 to the total of all the Trace Values of all the LDLs you passed through during your run.
Example: Spider's most recent run has taken her through Salt Lake (1), Denver (2), New Orleans (3), Havana (3). Bogota (4) and Rio (2). In Rio, she encounters a Hellhound (Strength 6) which attacks her outside of the Petrochem's new Data Fortress. Spider jacks out, and the Hellhound tries to run a trace back to her original position. It must beat a total of fifteen (1+2+3+3+4+2=15) in order. to make a successful trace. That Hellhound better roll a 9 or 10, or it's going to be out in the cold.