Bluetooth™ has three defined security modes, these are:
Security Mode 1: This is a non-secure mode, since the device will not initiate any security.
Security Mode 2: This provides a service level enforced security mode. It provides a flexible access security method by allowing multiple applications to use different security requirements in parallel.
Security Mode 3: This is a link level enforced security mode. The Bluetooth™ device will initiate security procedures before the link is set-up.