A cyberattack has hit over 1,000 American businesses including Supervalu, Target and United Postal Service (UPS).

The cyberattack struck the in-store cash register systems of various stores, said the United States Department of Homeland Security.

The department issued an advisory saying millions of American payment cards were affected and their data stolen without the target companies being aware of the attack.

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On July 31, Homeland Security along with the Secret Service, the National Cybersecurity and Communications Integration Center and their partners in the security industry ordered businesses to check their in-store cash register systems and see if a malware package called Backoff appeared in its code.

Since the warning, seven companies that sell and manage in-store cash register systems confirmed to the government their clients were affected by the cyberattack.

Supervalu, Target and UPS stepped forward to confirm the hack. The Secret Service said more than 1,000 companies which they had not checked confirmed they were affected.

The Secret Service said hackers are actively inspecting corporate systems to check if there are remote access opportunities.

After gaining remote access, hackers will deploy computers to guess usernames and passwords until they find a working combination.

The footprints they'll gain will be used to crawl through a corporate network until they access the in-store cash register systems. Criminals will then be able to collect payment card data from the cash register systems and send it back to their servers abroad.

Businesses and corporate companies need to take this cyberattack seriously and upgrade their payments systems to protect consumers, said the government.

TagsCyberattack, COMPUTER SECURITY, Security, HOMELAND SECURITY DEPARTMENT, Secret Service