KnowBe4 Warns of Rise in Microsoft Exchange Global Security Exploit Attempts

Complete environment takeovers, account impersonations and ransomware threats possible; security patching is recommended immediately

KnowBe4, the provider of the world’s largest security awareness training and simulated phishing platform, today issued a warning regarding the Microsoft Exchange exploit, affecting tens of thousands of accounts around the world.

Security threats from this exploit range from takeovers of servers which can result in complete environment takeovers to account impersonations to ransomware. Once a hacker gets into a server, they can take over every part of an organization’s environment, join an existing email thread and add malicious links and attachments into a conversation. Cybersecurity attacks are targeting unpatched Microsoft Exchange servers using a new strain of ransomware called “DearCry”. These attacks can encrypt computer systems and aim to gather payment from users.

“This Microsoft Exchange security issue has had a massive impact with far-reaching consequences,” said Stu Sjouwerman, CEO, KnowBe4. “Once a hacker gets into the system and accesses the server that controls all of the email accounts, they can completely take over an environment and really wreak havoc. Account impersonation is incredibly dangerous because the recipient of the email believes that they are speaking to the trusted party via email, so they are much more likely to click on a malicious link or open an infected email attachment. Ransomware is another one of the potential cybersecurity problems that threaten the operational capabilities of businesses that have not patched their systems yet due to this exploit. For any organization using Microsoft Exchange servers, it is recommended to patch immediately.”

Microsoft says that after the “initial compromise of unpatched on-premises Exchange Servers” ransomware is deployed on vulnerable systems, a situation reminiscent of the 2017 WannaCry outbreak. The tech giant is urging customers to apply the updates as soon as possible due to the critical nature of the security issues.

For more information, visit the KnowBe4 Blog or view our webinar, “Microsoft Exchange Mass Hack” at

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