Microsoft releases IOC Detection Tool for Microsoft Exchange Server flaws

After the disclosure of Microsoft Exchange zero-days, MS Exchange Server team has released a script to determine if an install is vulnerable.

This week Microsoft has released emergency out-of-band security updates that address four zero-day issues (CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065) in all supported MS Exchange versions that are actively exploited in the wild.

In response to the disclosure, the US Cybersecurity and Infrastructure Security Agency (CISA) has issued the Emergency Directive 21-02 in response to the disclosure of zero-day vulnerabilities in Microsoft Exchange.

Microsoft revealed that at least one China-linked APT group, tracked as HAFNIUM, chained these vulnerabilities to access on-premises Exchange servers to access email accounts, and install backdoors to maintain access to victim environments.

The US CISA’s emergency directive orders federal agencies to urgently update or disconnect MS Exchange on-premises installs.

Researchers at the MS Exchange Server team have released a script that could be used by administrators to check if their installs are vulnerable to the recently disclosed vulnerabilities.

Microsoft released the tool as open-source on GitHub, it can be used to check the status of Exchange servers.

“Formerly known as Test-Hafnium, this script automates all four of the commands found in the Hafnium blog post.” states Microsoft. “It also has a progress bar and some performance tweaks to make the CVE-2021-26855 test run much faster.

Download the latest release here: Download Test-ProxyLogon.ps1

The most typical usage of this script is to check all Exchange servers and save the output,”

The script automates the tests for the four zero-day vulnerabilities in Microsoft Exchange Server.

“Microsoft has released an updated script that scans Exchange log files for indicators of compromise (IOCs) associated with the vulnerabilities disclosed on March 2, 2021.” states CISA.

“CISA is aware of widespread domestic and international exploitation of these vulnerabilities and strongly recommends organizations run the Test-ProxyLogon.ps1 script—as soon as possible—to help determine whether their systems are compromised. For additional information on the script, see Microsoft’s blog HAFNIUM targeting Exchange Servers with 0-day exploits.”

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Pierluigi Paganini

(SecurityAffairs – hacking, MS Exchange)

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Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.