Here is a brief list of your travelling options according to security status:

Players with -2.0 or worse will be attacked in 1.0 systems
Players with -2.5 or worse will be attacked in 0.9 systems
Players with -3.0 or worse will be attacked in 0.8 systems
Players with -3.5 or worse will be attacked in 0.7 systems
Players with -4.0 or worse will be attacked in 0.6 systems
Players with -4.5 or worse will be attacked in 0.5 systems