National Grid Plc is fending off “huge amounts” of cyber-security threats, though only a handful have penetrated the company’s computer systems, Chief Executive Officer Steve Holliday said.

The U.K. electricity-grid operator — which also owns and operates power and gas networks in New York, Massachusetts and Rhode Island — has identified some attacks from the Middle East and “a lot from China,” Holliday said in an interview at a Bloomberg New Energy Finance conference in London.

“The number of penetrations that have gotten into our system in some way — and then we’ve found them and gotten rid of them — you can count those on one hand,” Holliday said. “But they’re still there.”

The government said in December it’s increasing spending on its cyber-security program by almost a third to 860 million pounds ($1.3 billion). Holliday said National Grid works with both the U.S. and U.K. governments to identify and fight threats. The company logs every incident, whether it’s an employee inputting an incorrect password three times, or a genuine effort to hack the grid operator’s systems.

“One of the things I always worry about in this space, as others do, is that there’s an inevitability that you’re actually solving the problems that you know about rather than problems that you can’t anticipate,” Holliday said.

“There are people who have got automatic programs that are running that are shooting things into the systems to try and find a weak spot,” he said. “That noise is in the background every day of the week, 24 hours a day. It’s a huge number.”