More than 1,000 American businesses have been affected by the cyberattack that hit the in-store cash register systems at Target, Supervalu and most recently UPS Stores. The attacks are much more pervasive than previously reported, and hackers are pilfering the data of millions of payment cards from American consumers without companies knowing about it, according to a new Department of Homeland Security advisory released Friday afternoon. On July 31, Homeland Security along with the Secret Service, the National Cybersecurity and Communications Integration Center and their partners in the security industry warned companies to check their in-store cash register systems for malware, which security experts dubbed “Backoff” after a word that appeared in its code. Until that point, Backoff malware and variations of it were undetectable by anti-virus products.