A customer waits at the counter of a CVS Pharmacy store in Pasadena, U.S., May 2, 2016. REUTERS/Mario Anzuoni/File Photo
A customer waits at the counter of a CVS Pharmacy store in Pasadena
  • A high-profile ransomware gang is responsible for the outage that has paralyzed US pharmacies, Reuters reported.
  • Blackcat is behind the attack on UnitedHealth Group's claims management arm last week, per the report.
  • The outage has caused a major backlog in filling customer prescriptions.

A notorious gang of hackers is behind an outage that has disrupted pharmacy deliveries across the country for nearly a week, according to a new report.