Microsoft Exchange Target of Hacks

29. March 2021

Microsoft’s Exchange Servers are exposed to an ever-increasing number of attacks. This is the second major cyberattack on Microsoft in recent months, following the so-called SolarWinds hack (please see our blog post). The new attacks are based on vulnerabilities that have been in the code for some time but have only recently been discovered.

In a blog post published on March 2nd, 2021, Microsoft explains the hack and a total of four found vulnerabilities. The first vulnerability allows attackers to gain access to a Microsoft Exchange Server, the second vulnerability allows them to execute their code on the system, and the third and fourth vulnerabilities allow the hacker write access to arbitrary files on the server. Microsoft Exchange Server versions 2019, 2016, 2013 and 2010 are affected, and Microsoft released a security update for all of them on March 2nd, even though support for Microsoft Exchange Server 2010 ended in October 2020.

Reportedly, Microsoft was informed about the vulnerability in January. Since then, a growing number of hacker groups have started to use the exploit. The initial campaign is attributed to HAFNIUM, a group believed to be state-sponsored and operating out of China. According to Microsoft, the vulnerabilities have been in the code for many years without being discovered. Only recently has Microsoft become aware of these vulnerabilities and begun working on them. Microsoft shared information on the vulnerability through the Microsoft Active Protections Program (Mapp), where they share information with a group of 80 security companies. The attacks began shortly after Microsoft began working to resolve the vulnerabilities. There are many similarities between the code Microsoft shared through Mapp and the code the attackers are using.

In an article about a recently published One-Click Exchange On-premises Mitigation Tool (EOMT), Microsoft developers describe how admins can secure Exchange servers against the current attacks within a very short amount of time. The tool only serves as an initial protective measure. For comprehensive protection, available security updates must be installed. In addition, it must be checked whether the hackers have already exploited existing gaps to leave behind backdoors and malware. This is because the updates close the gaps, but do not eliminate an infection that has already occurred. Hackers often do not use gaps immediately for an attack, but to gain access later, for example for large-scale blackmail.

Under the General Data Protection Regulation (GDPR), organizations affected by an attack on personal data must, in certain circumstances, report such an incident to the relevant supervisory authority and possibly to the affected individuals. Even after a successful patch, it should be kept in mind that affected organizations were vulnerable in the meantime. Pursuant to Art. 33 of the GDPR, system compromises that may affect personal data and result in a risk to data subjects must be notified to the competent supervisory authority. For such a notification, the time of discovery of the security breach, the origin of the security breach, the possible scope of the personal data affected, and the first measures taken must be documented.