Cimbi the guardian (???)

I must admit that we do not think of Cimbora as a guard dog.  He is friendly with almost everybody and we think that he would great a burglar with wagging tail and big kisses. He is a big soft thing, a bundle of love, really.
Or maybe there are other sides to his character? Or is he just a well-balanced dog who knows what to do but without unnecessary aggression?
Yesterday we got to the Obuda Island (the big park where we always go to meet well-socialized dogs) late, after dark (but this is another story). There is an illuminated path for the walkers (the whole island cannot be illuminated of course). It was a quiet evening, we were too early for the dogs coming for their evening walk and too late for the afternoon walk. We were walking along this path, Cimbi ahead of us reading the news, when suddenly a runner appered from the dark to our left - he was probably coming from the bank of the river. We would not even have noticed him but for Cimbora who rushed to be between us and the runner - stopped almost exactly between him and us - and started to bark. Poor runner got a heart attack and stopped. Cimbi did not move but when he saw that the guy was not moving he stopped barking. Then the guy realized that the dog was not alone and started to run again however as soon as he started moving, Cimbi also started to bark. We had to call him back and keep him by the collar until the runner disappeared. It seemed that he told this "dangerous" runner: Hey you there! Do not come any closer!
Hubby says that he obviosuly protected us. Well, I am not so sure, he is still far from being a grown up dog, but one thing I do know: we LOVE him, lol.