HOUSTON, Aug 21 (Reuters) -

U.S. oilfield services firm Halliburton ( HAL ) on Wednesday

was hit by a cyberattack, according to a person familiar with

the matter.

Halliburton ( HAL ) said it was aware of an issue affecting certain

systems at the company and was working to determine the cause

and impact of the problem. The company was also working with

"leading external experts" to fix the issue, a spokesperson said

in an emailed statement.

The attack appeared to impact business operations at the

company's north Houston campus, as well as some global

connectivity networks, the person said, who declined to be

identified because they were not authorized to speak on the

record.

The company has asked some staff not to connect to internal

networks, the person said.

Houston, Texas-based Halliburton ( HAL ) is one of the largest

oilfield services firms in the world, providing drilling

services and equipment to major energy producers around the

globe. It had nearly 48,000 employees and operated in more than

70 countries at the end of last year.

Cyberattacks have been a major headache for the energy

industry. In 2021, hackers attacked the Colonial Pipeline with

ransomware, causing a days-long shutdown to the major fuel

supply line.

That breach, which the FBI attributed to a gang called

DarkSide, led to a spike in gasoline prices, panic buying and

localized fuel shortages.

Several major U.S. companies have suffered ransomware

attacks in recent years, including UnitedHealth Group ( UNH ),

gambling giants MGM Resorts International ( MGM ), Caesars

Entertainment CZR.O and consumer good maker Clorox.

While its unclear what exactly is happening at

Halliburton ( HAL ), ransom software works by encrypting victims' data.

Typically, hackers will offer the victim a key in return for

cryptocurrency payments that can run into the hundreds of

thousands or even millions of dollars.

If the victim resists, hackers sometimes threaten to

leak confidential data in a bid to pile on the pressure.

The ransomware group DarkSide, suspected by U.S.

authorities of the Colonial Pipeline attack, for example, said

it wanted to make money. Colonial Pipeline's CEO said his

company paid a $4.4 million ransom as executives were unsure how

badly its systems were breached or how long it would take to

restore the pipeline.

(Reporting by Liz Hampton in Denver and Chris Sanders in

Washington)