Coinbase falls after co says it expects up to $400 mln hit from cyber attack

Shares of cryptocurrency exchange Coinbase Global COIN.O fall 1.8% to $258.67 in premarket

Co says it expects to incur between $180 million and $400 million in costs related to a cyber attack

COIN says cyber criminals had stolen account data for a "small subset" of its customers

However, COIN says no passwords, private keys, or funds were exposed and Coinbase Prime accounts are untouched

The company will not pay the $20 million ransom demand it received and says it will reimburse the customers who were tricked into sending funds to the attackers

COIN says it has set up a $20 million reward for information on the attackers

Earlier in the week, the company became the first digital asset player to be included in the benchmark S&P 500 index .SPX

As of last close, COIN has gained nearly 6% YTD