The value of bitcoin slumped more than 7 percent Monday after news emerged that a little-known South Korean cryptocurrency was targeted by hackers over the weekend. Cryptocurrency exchange Coinrail announced Sunday that it had been breached, with its system hit by a “cyberintrusion” that caused the loss of about 30 percent of its coins traded. Local news outlets estimated that amounts to about 40 billion won ($37 million) in of virtual coins. The heist at Coinrail sent the price of bitcoin tumbling to two-month lows and once again highlighted the security risks and weak regulation of global cryptocurrency markets. Coinrail said it had temporarily suspended trading in digital currencies and was fully cooperating with investigators to try to track down the missing funds. Bloomberg News put the wider crypto losses in market value at more than $42 billion.