Hi Larry,

I don’t have much experience with them. Secure communication requires pairing between the devices, which can be done in several ways, depending on the device capabilities. You can read about the pairing and encryption in this page, and read about BLE eavesdropping and packet injection in practice here.

From what I know, Bluetooth 4.2 introduced Elliptic curve Diffie–Hellman for key generation, which can help to improve the situation for secure communication.

As you say in your comments, most simple BLE device do not even bother to implement the security features, but at least the possibility is there :-)