Phosphorus also uses a technique whereby it sends people an email that makes it seem as if there’s a security risk to their accounts, prompting them to enter their credentials into a web form that enables the group to capture their passwords and gain access to their systems.

Both attack methods employ the use of websites that incorporate the names of well-known brands, like Microsoft, to appear authentic. Websites registered and used by Phosphorus include, for example, outlook-verify.net, yahoo-verify.net, verification-live.com, and myaccount-services.net.

While we’ve used daily security analytics tracking to stop individual Phosphorus attacks and notify impacted customers, the action we executed last week enabled us to take control of websites that are core to its operations. Our work to track Phosphorus over multiple years and observe its activity enabled us to build a decisive legal case and execute last week’s action with confidence we could have significant impact on the group’s infrastructure.