# Protection from a Parasite Chain Attack

In one variant of a Double Spending attack, the Parasite Chain attack, a malicious actor places a transaction of a specified value in the main DAG chain, while attempting to replicate this on a thread in an attempt to double-spend the tokens.

Netdex's blockchain protocol does not start with a main chain. It generates the main chain from threads of chains using a graph protocol related to network analysis in biological systems. This means that, theoretically, any thread can ultimately come to belong to the main chain. So, what prevents a malicious parasite chain from making a successful attack? 



A thread chain must have a parent chain for whom the verification of each Event Block can be successfully performed. This means that a parasite chain with a false history – the parasite thread will not be accepted unless the history it attests to reflects that of the main chain. Also, there must be a connection between the existing main chain and any thread to be added to it – preventing a parasite thread from creating a false history of Event Blocks and successfully merging. To successfully add a false history, more than 1/3rd of the nodes would have to be malicious.


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