Distributed ledgers stimulate innovative services and enabled new applications in several domains, creating new concepts for trust and regulation. However, this backbone that is enabling novelties and abridging businesses comes with drawbacks and security flaws. In this paper, we evaluate several Distributed Ledger Technologies (DLTs) features depicting the Bitcoin, Ripple, Ethereum, Hyperledger, Algorand and IOTA networks. We focus on their security challenges and expose numerous threats and vulnerabilities. For instance, we have simulated a few of their possible attacks proving them non-immune. In the other hand, we show a few of their malicious use cases. Meticulously presenting DLTs menaces and flaws, we are not involved in preferring any specific DLT network.