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.
RELATED RESOURCE
Managing security risk and compliance in a challenging landscape
How key technology partners grow with your organisation
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.
-
Cleo attack victim list grows as Hertz confirms customer data stolen – and security experts say it won't be the lastNews Hertz has confirmed it suffered a data breach as a result of the Cleo zero-day vulnerability in late 2024, with the car rental giant warning that customer data was stolen.
-
‘Phishing kits are a force multiplier': Cheap cyber crime kits can be bought on the dark web for less than $25 – and experts warn it’s lowering the barrier of entry for amateur hackersNews Research from NordVPN shows phishing kits are now widely available on the dark web and via messaging apps like Telegram, and are often selling for less than $25.
-
Healthcare systems are rife with exploits — and ransomware gangs have noticedNews Nearly nine-in-ten healthcare organizations have medical devices that are vulnerable to exploits, and ransomware groups are taking notice.
-
Alleged LockBit developer extradited to the USNews A Russian-Israeli man has been extradited to the US amid accusations of being a key LockBit ransomware developer.
-
February was the worst month on record for ransomware attacks – and one threat group had a field dayNews February 2025 was the worst month on record for the number of ransomware attacks, according to new research from Bitdefender.
-
CISA issues warning over Medusa ransomware after 300 victims from critical sectors impactedNews The Medusa ransomware as a Service operation compromised twice as many organizations at the start of 2025 compared to 2024
-
Warning issued over prolific 'Ghost' ransomware groupNews The Ghost ransomware group is known to act fast and exploit vulnerabilities in public-facing appliances
-
The Zservers takedown is another big win for law enforcementNews LockBit has been dealt another blow by law enforcement after Dutch police took 127 of its servers offline
