More than a decade since Google bought DoubleClick for a cool $3.1 billion, it’s estimated that Google’s ad network now reaches about 250 million unique viewers in the US alone.

But the company is being hit with a burgeoning number of cyber attacks, abusing DoubleClick in a bid to distribute moneymaking malware. The malware’s goal: to mine crypto-currency on infected computers and funnel earnings back to its criminal controllers.

The attack delivers Coinhive, a mining script that has legitimate applications but is being installed without permission.

This malware has been dubbed cryptojacking, and its use by criminal hackers has skyrocketed in recent months.