Players that have low security status provoke a police drone response when going into systems with a high security status. The thresholds for provoking a police drone response are follows:

System
Security / Security Standing
1.0: -2.0 and lower is safe.
0.9: -2.5 and lower is safe.
0.8: -3.0 and lower is safe.
0.7: -3.5 and lower is safe.
0.6: -4.5 and lower is safe.
0.4: No restrictions (low sec).