A ransomware attack has exposed the commercial and personal employee data of Artech Information Systems, one of the largest IT staffing agencies in the nation.

The data breach occurred Jan. 5 – 8 after a bad actor gained access to company servers through an employee user account, according to Bleeping Computer. Company officials said Social Security numbers, medical information, health insurance information, credit card payment information, passport numbers and other personally identifiable information may have been exposed in the breach.

Artech Information Systems has 10,500 employees and consultants and supplies staffing to more than 80 Fortune 500 clients as well as government agencies.

The REvil ransomware gang has allegedly claimed responsibility for the cyberattack, according to Bleeping Computer. The gang has asked for an undisclosed ransom amount or it will sell the data found on the serves to third parties.

After Artech Information Systems officials discovered the attack, they said they switched system credentials and improving security processes.

The company has sent out a notification letter to those affected by the data breach. The letter encourages those exposed to information to keep an eye on their account statements and monitor their credit report with identity theft protection.

Ransomware attacks targeting businesses and organizations have been rapidly increasing. Last year the number of targeted ransomware attacks was up 500% compared to the previous year.