Is there a way to conclude whether a Russian has Jews ancestors just from his surname?
Perhaps, first and foremost such surnames should not have Russian (Ukrainian, Belorussian, Tatar, etc) known roots. For example, Путин is derived from путь (the way).On the other hand, Фельдман sounds pretty Jewish to me. But you can easily confuse some Jewish surnames with Polish or German ones, if you are not an expert.