Microsoft Exchange exploits now used by cryptomining malware

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Microsoft Exchange exploits now used by cryptomining malware

The operators of Lemon_Duck, a cryptomining botnet that targets enterprise networks, are now using Microsoft Exchange ProxyLogon exploits in attacks against unpatched servers.

The malware is known for installing XMRig Monero (XMR) CPU coinminers on infected devices to mine cryptocurrency for the botnet’s owners.

Lemon_Duck’s ongoing attacks on vulnerable Exchange servers have already reached a massive scale, according to Costin Raiu, director of Kaspersky’s Global Research and Analysis Team.

The attackers are using web shells deployed on compromised servers to download malicious payloads from p.estonine[.]com and cdn.chatcdn[.]net.

These indicators of compromise associated with Lemon_Duck were also observed by Huntress Labs while analyzing mass exploitation of on-premises Microsoft Exchange servers.

Continuously updated cryptomining botnet

In previous attacks, the botnet was used to gain access to victims’ networks over the SMB protocol using EternalBlue or by brute-forcing Linux machines and MS SQL servers.

Lemon_Duck also supports spreading to servers running exposed Redis (REmote DIctionary Server) databases and Hadoop clusters managed using YARN (Yet Another Resource Negotiator).

Its operators also employed large-scale COVID-19-themed spam campaigns for propagation in the past, exploiting the CVE-2017-8570 Microsoft Office remote code execution (RCE) vulnerability to deliver the malware payload.

“The Lemon Duck cryptominer is one of the more advanced types of cryptojacker payloads we’ve seen,” Sophos security researcher Rajesh Nataraj said.

“Its creators continuously update the code with new threat vectors and obfuscation techniques to evade detection, and the miner itself is ‘fileless,’ meaning it remains memory resident and leaves no trace of itself on the victim’s filesystem.”

Exchange servers targeted by ransomware, state hackers

Since Microsoft disclosed ongoing attacks using ProxyLogon exploits last week, at least ten APT groups have been…