Two styles of online attack are more and more likely to affect Bitcoin in 2017, thanks mostly to its miner configuration.

A report by ETH Zurich titled “Hijacking Bitcoin: Routing Attacks on Cryptocurrencies” details how ISPs form the latest threat to Bitcoin stability through so-called partition and delay attacks.

In the first, an attacker can create “parallel Blockchains,” ETH writes, with the result that when the attack is over, the smaller chain will be dismissed.

“By preventing nodes within a component to communicate with nodes outside of it, the attacker forces the creation of parallel blockchains. After the attack stops, all blocks mined within the smaller component will be discarded together with all included transactions and the miners revenue,” the group says.

Bitcoin mining lies at the heart of the ISP weakness issue, as a considerable amount of network mining power (30 percent) is distributed across a comparatively small number of ISPs (13).

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“Moreover, most of the traffic exchanged between Bitcoin nodes traverse few ISPs,” ETH continues. “Indeed, our results indicate that 60% of all possible Bitcoin connections cross 3 ISPs. In other words, 3 ISPs can see 60% of all Bitcoin traffic.”

The delay attack, meanwhile, would facilitate delivery of a block to a node 20 minutes behind others, leaving it susceptible to double spends.

ETH stated the purpose of the research was to inform the Bitcoin users and miners as well as suggest long and short-term countermeasures.