Microsoft warns of ransomware attacks as Exchange hack escalates

Microsoft Exchange users are now being targeted by ransom-seeking hackers, according to the latest findings from Microsoft Defender researchers.

The popular email server had been hit by at least ten hacking groups, including Chinese state-backed cyber criminals, who had taken advantage of four zero-day vulnerabilities.

Security program manager Philip Misner reported on Thursday that Exchange users now also need to watch out for “human-operated ransomware attacks”, with the threat to customers escalating as a result.

The ransomware, also known as DearCry, is typical in its approach, preventing users from being able to use their PCs or access their data until a payment is sent to hackers, according to information outlined by Microsoft.

“We have detected and are now blocking a new family of ransomware being used after an initial compromise of unpatched on-premises Exchange Servers,” Microsoft’s Security Intelligence team informed its Twitter followers.

This follows reports that a proof-of-concept tool to hack Microsoft Exchange servers has been published on Microsoft-owned GitHub.

Vietnam-based independent security researcher Nguyen Jang is believed to have shared the first functional public proof-of-concept exploit for a group of vulnerabilities in Microsoft Exchange servers known as ProxyLogon, according to reports by The Record.

A GitHub spokesperson told Vice that although “the publication and distribution of proof of concept exploit code has educational and research value to the security community”, its “goal is to balance that benefit with keeping the broader ecosystem safe”.

“In accordance with our Acceptable Use Policies, we disabled the gist following reports that it contains proof of concept code for a recently disclosed vulnerability that is being actively exploited,” they added.

Although the code was removed from GitHub mere hours after, its publishing could have still exacerbated an already dire situation for Exchange users.

Among the hundreds of thousands of victims are high-profile and political organisations such as the Norwegian government, which earlier this week reported that it had data stolen as a result. Reuters reported that up to 60,000 networks remain vulnerable in Germany alone.

Microsoft has advised on-premises Exchange Server customers to prioritise the security updates outlined here.