How weak passwords and other failings led to catastrophic breach of Ascension

Last week, a prominent US senator called on the Federal Trade Commission to investigate Microsoft for cybersecurity negligence over the role it played last year in health giant Ascension's ransomware breach, which caused life-threatening disruptions at 140 hospitals and put the medical records of 5.6 million patients into the hands of the attackers. Lost in the focus on Microsoft was something as, or more, urgent: never-before-revealed details that now invite scrutiny of Ascension’s own security failings.

In a letter sent last week to FTC Chairman Andrew Ferguson, Sen. Ron Wyden (D-Ore.) said an investigation by his office determined that the hack began in February 2024 with the infection of a contractor's laptop after they downloaded malware from a link returned by Microsoft’s Bing search engine. The attackers then pivoted from the contractor device to Ascension’s most valuable network asset: the Windows Active Directory, a tool administrators use to create and delete user accounts and manage system privileges to them. Obtaining control of the Active Directory is tantamount to obtaining a master key that will open any door in a restricted building.

Wyden blasted Microsoft for its continued support of its three-decades-old implementation of the Kerberos authentication protocol that uses an insecure cipher and, as the senator noted, exposes customers to precisely the type of breach Ascension suffered. Although modern versions of Active Directory by default will use a more secure authentication mechanism, it will by default fall back to the weaker one in the event a device on the network—including one that has been infected with malware—sends an authentication request that uses it. That enabled the attackers to perform Kerberoasting, a form of attack that Wyden said the attackers used to pivot from the contractor laptop directly to the crown jewel of Ascension’s network security.

A researcher asks: “Why?”

Left out of Wyden’s letter—and in social media posts that discussed it—was any scrutiny of Ascension’s role in the breach, which, based on Wyden’s account, was considerable. Chief among the suspected security lapses is a weak password. By definition, Kerberoasting attacks work only when a password is weak enough to be cracked, raising questions about the strength of the one the Ascension ransomware attackers compromised.