Blockchain technology is being considered as one of the ultimate revolutions that will be able to disrupt several pillars of our society. It is a public and distributed ledger built for security and interoperability. Blockchain provides all parties a secure and synchronized record of immutable transactions assembled together and permanently stored with a fingerprint, creating therefore an irreversible chain. In order to operate, this technology does not rely on any central authority. All transactions are sent over the network and the consensus is achieved by the mutual calculation and agreement. In this paper, we evaluate the blockchain technology and its evolution. Then, we characterize some essential features of the distributed ledger technologies (DLT) focusing on the three main blockchains actors: Bitcoin, Ethereum and Hyperledger. Besides, we present their security challenges and explore their drawbacks that can lead to use the blockchain network in order to conduct several attack scenarios. Finally, we describe their relationship with the onion router network (Tor) that beyond the malicious uses of the blockchain via Tor, these two networks share many common points.