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A popular payroll and timekeeping system used by hundreds of companies, including many in Chicago, has been hit by a large-scale ransomware attack.

“Ultimate Kronos Group,” known as UKG, is a payroll software relied on by 40 million workers. On Tuesday, the company issued a statement saying services were disrupted due to the attack.

Many companies, including Marriott Hotels were affected.

Chicago-based cyber security expert Elijah Anderson said ransomware attacks are becoming more commonplace.

“Ransomware is something that has a lot of permutations out there today, so it’s hard to even define because its constantly evolving,” Anderson said.

Anderson said it’s too early to tell who is responsible for the incident.

“This as an opportunity of growth and the technology is so simple to use and affordable, that anyone with a laptop and time on the internet in a Dark Web forum can learn the basics to be dangerous,” said Anderson.

Anderson said there are certain vulnerabilities in software that every company can address no matter their size — like changing passwords and two-factor authentication for logging into internal web sites.

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At this time, it’s unclear how the ransomware attack on Kronos will impact upcoming paychecks.