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Microsoft Spots Multiple Nation-State APTs Exploiting Log4j Flaw

If defenders needed any more urgency to patch and mitigate the explosive Log4j zero-day, along comes word that APT actors linked to China, Iran, North Korea and Turkey have already pounced and are actively exploiting the CVSS 10.0 vulnerability.

Security response teams at Microsoft on Wednesday confirmed nation-state hackers are poking at CVE-2021-44228 (the identifier for the Log4j vulnerability) to launch high-end malware implants.

Redmond’s Threat Intelligence Center (MSTIC) expressly identified nation-state backed hacking teams from China, Iran, North Korea, and Turkey as the adversaries exploiting the flaw.

“This activity ranges from experimentation during development, integration of the vulnerability to in-the-wild payload deployment, and exploitation against targets to achieve the actor’s objectives,” Microsoft said in a note on Log4j exploitation.

Microsoft’s findings confirm earlier reports from Mandiant that nation-state backed groups have added the Log4j exploit to malware toolkits.

[ READ: Exploits Swirling for Major Security Defect in Apache Log4j ]

Microsoft said the Iranian threat actor tracked as PHOSPHORUS (also known as Charming Kitten) has been seen acquiring and making modifications to the Log4j exploit for use in the wild. 

“We assess that PHOSPHORUS has operationalized these modifications,” Microsoft warned, noting that the Iranian hacking group has been actively deploying ransomware for use in data extortion attacks.

Microsoft’s threat hunters said it also spotted HAFNIUM, a known threat actor group operating out of China, exploiting the Log4j vulnerability to attack virtualization infrastructure to extend typical APT targeting. 

“In these attacks, HAFNIUM-associated systems were observed using a DNS service typically associated with testing activity to fingerprint systems,” MIcrosoft warned.

The company did not share any specific information on observed hacking attacks from North Korea or Turkey.

[ SEE: Log4Shell Tools and Resources for Defenders - Continuously Updated ]

Microsoft also confirmed that multiple cybercrime groups that act as “access brokers” have started abusing the CVE-2021-44228 bug on both Windows and Linux systems to gain initial access to target networks. These access brokers then sell access to these networks to ransomware-as-a-service affiliates. 

Microsoft expects to see a surge in human-operated ransomware attacks on both Windows and Linux servers.

The software giant also observed signs of malicious botnet operators pouncing on the security defect to add compromised machines into computing pools to use for phishing and denial-of-service attacks.

“Microsoft has observed rapid uptake of this vulnerability into existing botnets like Mirai, existing campaigns previously targeting vulnerable Elasticsearch systems to deploy cryptocurrency miners, and activity deploying the Tsunami backdoor to Linux systems,” the company said.  

“Many of these campaigns are running concurrent scanning and exploitation activities for both Windows and Linux systems, using Base64 commands included in the JDNI:ldap:// request to launch bash commands on Linux and PowerShell on Windows,” the company added.

Related: Industrial Organizations Targeted in Log4Shell Attacks

Related: EXPLAINER: The Security Flaw That's Freaked Out the Internet   

Related: Log4Shell Tools and Resources for Defenders (Continuously Updated)

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Ryan Naraine is Editor-at-Large at SecurityWeek and host of the popular Security Conversations podcast series. Ryan is a veteran cybersecurity strategist who has built security engagement programs at major global brands, including Intel Corp., Bishop Fox and Kaspersky GReAT. He is a co-founder of Threatpost and the global SAS conference series. Ryan's past career as a security journalist included bylines at major technology publications including Ziff Davis eWEEK, CBS Interactive's ZDNet, PCMag and PC World. Ryan is a director of the Security Tinkerers non-profit, an advisor to early-stage entrepreneurs, and a regular speaker at security conferences around the world. Follow Ryan on Twitter @ryanaraine.