Health network officials have described the attack as “highly sophisticated” and claim attackers used an undiscovered bug in software known as a zero-day to breach their systems. They did not name the affected software and did not provide evidence to back up their claims.However, FireEye, the cybersecurity firm, released a report last month that found a ransomware group used a zero-day in SonicWall VPN security devices to breach organizations. Typically, ransomware gangs are known to break in using unpatched software, weak passwords or phishing attacks. The use of zero-days would mark a major advance in criminals’ tactics, and increase …
