diff --git a/components/ble/ble_services/ble_dfu/ble_dfu_unbonded.c b/components/ble/ble_services/ble_dfu/ble_dfu_unbonded.c
index f6d09a4..df7c08a 100644
--- a/components/ble/ble_services/ble_dfu/ble_dfu_unbonded.c
+++ b/components/ble/ble_services/ble_dfu/ble_dfu_unbonded.c
@@ -216,9 +216,9 @@ uint32_t ble_dfu_buttonless_char_add(ble_dfu_buttonless_t * p_dfu)
     add_char_params.is_var_len          = true;
     add_char_params.max_len             = BLE_GATT_ATT_MTU_DEFAULT;
 
-    add_char_params.cccd_write_access = SEC_OPEN;
-    add_char_params.write_access      = SEC_OPEN;
-    add_char_params.read_access       = SEC_OPEN;
+    add_char_params.cccd_write_access = SEC_MITM;
+    add_char_params.write_access      = SEC_MITM;
+    add_char_params.read_access       = SEC_MITM;
 
     return characteristic_add(p_dfu->service_handle, &add_char_params, &p_dfu->control_point_char);
 }