When Samaritan goes online, Machine creates 7 secret identity and Root accquire 7 servers to put make blindspot to save people related to Machine.
Below are seven persons :-

1. Harold Finch
2. John Reese
3. Sameen Shaw
4. Samantha Groves (Root)
5. Daniel Casey
6. Daizo
7. Jason Greenfield

Samaritan is smart that it founds the connection of Harold with Grace Hendricks, even when he is not meeting her and she believes him dead. On the other hand,
Detective Fusco is helping them from long time. He had been on many places with them and also actively helped them.
Then why is Machine not needed to create blindspot for him. 
In other words, why Samaritan is not able to find the connection between Detective Fusco and John & Harold