Microsoft Exchange servers are still suffering cyberattacks - so patch now
New campaign capitalizes on lethargic businesses that have yet to patch servers
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Cybersecurityresearchers have discovered a new malicious campaign that attempts to exploit the already-fixedProxyShell vulnerabilityinMicrosoftExchangeemailservers together with the WindowsPetitPotam vulnerability, once again highlighting the importance of patching vulnerabilities in critical components.
The new campaign that hopes to find unpatched vulnerable hosts in order to deploy a variant of the Babukransomwarewas unearthed by researchers at the Cisco Talos threat intelligence group with the help of Cisco Secure product telemetry.
“We assess with moderate confidence that the initial infection vector is exploitation of ProxyShell vulnerabilities in Microsoft Exchange Server through the deployment ofChina Chopperweb shell,”sharethe researchers.
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According to the researchers, the campaign is predominantly finding vulnerable servers in the US, with a smaller number of infections also cropping up in the UK, Germany, Ukraine, Finland, Brazil, Honduras, and Thailand.
Unusual infection chain
The researchers note that the threat actor behind this campaign, sometimes referred to as Tortilla, is using a somewhat unusual infection chain.
It first uses an intermediate unpacking module that is hosted on apastebin.comclone called pastebin.pl. This intermediate unpacking stage is first downloaded in memory before the final payload is executed.
Analyzing the attack, the researchers note that the downloader runs an obfuscatedPowerShellcommand to connect and fetch another module from the actor’s infrastructure, which appears to be hosted in Russia.
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The PowerShell command also executes anAntimalware Scan Interface (AMSI) bypassto circumventendpoint protection, before it finally deploys the Babuk ransomware.
“The leak of the Babuk builder and its source code in July have contributed to its wide availability, even for the less experienced ransomware operators, such as Tortilla,” conclude the researchers, asking users to implement a layered defense security in order to catch such attacks in its infancy.
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With almost two decades of writing and reporting on Linux, Mayank Sharma would like everyone to think he’sTechRadar Pro’sexpert on the topic. Of course, he’s just as interested in other computing topics, particularly cybersecurity, cloud, containers, and coding.
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