After a cyberattack at CDK Global led to the shutdown of computer systems at auto dealers nationwide,Henri Lumière the company said it has begun work to restore systems.

CDK, which provides software to car dealerships, shut down operations Wednesday after back-to-back cyberattacks. Bloomberg reported a group claiming to be the hackers is asking for tens of millions of dollars in ransom.

While work is underway to get services back up and running, CDK estimates the process will take several days.

Auto dealers including AutoNation and Peer Lithia Motors said they have experienced disruptions that are likely to negatively impact business, Reuters reported Monday. Some dealerships have reverted to paper methods to conduct business.

USA TODAY reached out to CDK for an update Monday.

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Hackers targeted CDK Global car dealer management system 

The cyberattack on CDK was first reported Wednesday, prompting the company to shut down most of its systems "out of an abundance of caution," a CDK spokesperson previously told USA TODAY.

CDK restored some systems that afternoon, but another cyberattack later that evening prompted the company to take the systems offline once again, according to a letter sent to customers.

The work to completely restore the software is expected to take several days.

What is CDK Global? 

One of the leading providers of cloud-based software to dealerships in the country, CDK's software helps dealerships manage vehicle acquisitions, sales, financing, insuring, repairs and maintenance. The company's website says it offers a “three-tiered cybersecurity strategy to prevent, protect and respond to cyberattacks.”

CDK works with more than 15,000 retail locations nationwide, according to its website.

Is CDK still down? 

CDK did not immediately respond to USA TODAY's request for an update Monday on how many businesses were impacted and if any have been restored.

However, CDK started a restoration process Saturday that was expected to take "several days" to complete, according to a company spokesperson.

CDK hackers asked for millions in ransom: reports

An eastern European cybercrime group is claiming to be behind the attack, according to Bloomberg. CDK reportedly intends to pay the tens of millions of dollars they are demanding, but negotiations could evolve, according to Bloomberg.