A method for blockchain nodes, the method including: sending security data of an Internet of Things system to other blockchain nodes, so that each blockchain node stores the security data in a blockchain database for that blockchain node; and obtaining one or more pieces of security data of the Internet of Things system from a blockchain database for a current blockchain node, and performing a corresponding operation on the Internet of Things system based on the obtained security data. There is also provided a device, a computer system and a computer readable medium for blockchain nodes.