In recent years, blockchain technology has witnessed remarkable developments in its application to crypto assets (cryptocurrency) considering not only function storing values but also extension of the smart contract and anonymity improvement. Ethereum is a blockchain that features the smart contract and there is a data space, where programs can be freely stored, on the blockchain. However, pollution of such data space can jeopardize the existence of Ethereum.In this study, we analyze the fact that the malicious files that are stored in the data space of Ethereum and discuss “blockchain poisoning attacks” that significantly contaminate the blockchains by embedding malicious data at a relatively lower cost. We try to tackle Ethereum-specific risks which are not mentioned in previous study. In addition, we empirically examine the possibility of a poisoning attack on a private blockchain network.