United Hoster

United Hoster is a hosting provider with its headquarters located in Germany. The company’s primary offering is a Hosted Exchange service, whereby it runs Microsoft Exchange servers on behalf of its customers. This service includes the provision of mail databases that store users’ email, calendar, contacts and related data. By managing the underlying infrastructure, United Hoster enables clients to access a fully featured Exchange environment without having to maintain the hardware or software themselves. The firm operates within the broader market for managed cloud services, focusing specifically on email and collaboration platforms.

On 20 May 2023, United Hoster disclosed that its Hosted Exchange platform had been hit by a ransomware attack. The attackers succeeded in encrypting the mail databases hosted on the Exchange servers, which caused the email service to go offline for affected customers. In its public statement, the company said there was no evidence that any data had been exfiltrated from the compromised systems. United Hoster also noted that no ransom demand had been received as part of the incident. Forensic analysis indicated that the intrusion was made possible by exploiting a previously unknown vulnerability in the Microsoft Exchange software that underpins the hosted offering.

Following the discovery of the breach, United Hoster promptly notified the relevant law‑enforcement agencies and began an internal investigation. To limit disruption for its users, the provider supplied an alternative mail solution while it worked to construct a clean, replacement Exchange environment. The response effort included applying countermeasures designed to address the specific vulnerability that had been exploited. Once the new infrastructure was validated, United Hoster restored normal service operation for its customers. The episode underscored the risks associated with managing critical email platforms and highlighted the importance of rapid incident response and transparent communication.