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CISA is aware of threat actors using open source tools to search for vulnerable Microsoft Exchange Servers and advises entities to investigate for signs of a compromise from at least September 1, 2020. CISA has updated the Alert on the Microsoft Exchange server vulnerabilities with additional detailed mitigations. 
CISA encourages administrators to review the updated Alert and the Microsoft Security Update and apply the necessary updates as soon as possible or disconnect vulnerable Exchange servers from the internet until the necessary patch is made available.

Brought to you by Dr. Ware, Microsoft Office 365 Silver Partner, Charleston SC.