If you have enough people, I would create a security barrier. Like security outposts to detect unwanted guests, and give that guest the impression, you are acting on your own.
That would be the first barrier. The guest is stopped in an area where he is unable to see the camp, for example in 100 meters (300 ft) from the camp.
The "security guard" will investigate the persons intentions and will not have any radio-contact with others to reveal that he is in contact with others, only when in danger.
You will also need a second security person hidden with the investigating security person that's in some discreet communication with the base camp.