Barely into the new year, Ethereum Classic (ETC), an offshoot of Ethereum (ETH) and the 18th-largest cryptocurrency by market cap, was subject to a "51% attack" – a type of hack possible on cryptocurrencies using a proof-of-work (POW) protocol. In essence, a single entity or group gains a majority of the network hash rate, enabling it to rewrite blockchain data and therefore "double-spend" ‒ sell cryptocurrency for fiat, and then amend the ledger to get the coins back, while keeping the fiat. Reports indicate that nearly $1 million worth of ETC was stolen in the recent attack. A Chinese security firm, SlowMist, published technical details on the attack and claimed it may be able to identify more information on the attacker if certain cryptocurrency exchanges assisted by providing information. This news comes on the heels of The Ethereum Foundation's announcement that it will slash energy consumption in 2019 by replacing POW with a proof-of-stake protocol, which cuts energy consumed per Ethereum transaction. In addition to ecological benefits, the protocol switch may thwart these kinds of thefts, although it is unclear whether other types of attacks will be made possible.

But POW-targeted attacks are hardly the only kind of theft in crypto news. A new study reports a staggering 4,000 percent rise this year in cryptocurrency mining malware ‒ malware used by criminals to hack into an innocent user's computer, smartphone or other device in order to harness processing power to use for mining cryptocurrencies. The study estimates that illicit crypto-mining was responsible for nearly $57 million in revenue. The most popular cryptocurrency was Monero, 4.3 percent of which was mined through the use of illicit malware. Bitcoin was the second-most-targeted currency, but its popularity has declined over the past three years due to an increase in hash rate and difficulty in mining.

Conventional bitcoin wallet attacks continue as well. According to reports last week, a hack targeted at the Electrum bitcoin wallet provider stole approximately $750,000 worth of bitcoin from Electrum wallet users.

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