Paper reviews a mining algorithm in smart city’s blockchain systems with the Proof-of-Work consensus mechanism. Related studies in the field of detecting selfish mining attacks are reviewed. A method for protecting blockchain from selfish mining is presented. A plug-in for detecting selfish mining for the miner software is developed which allows analyzing patterns in data coming from the mining pool. The proposed solution outperforms other selfish mining detectors as it allows identifying the attacking pool and has lower error rates.