Sophisticated attackers used DazzleSpy macOS backdoor in watering hole attacks

Pierluigi Paganini January 25, 2022

Experts found an undocumented macOS backdoor, dubbed DazzleSpy, that was employed in watering hole attacks aimed at politically active individuals in Hong Kong.

Researchers from ESET have spotted an undocumented macOS backdoor, dubbed DazzleSpy, that was employed in watering hole attacks aimed at politically active individuals in Hong Kong.

The investigation started in November after Google TAG published a blogpost about watering-hole attacks targeting macOS users in Hong Kong.

Google TAG researchers discovered that threat actors leveraged a zero-day vulnerability in macOS in a watering hole campaign aimed at delivering malware to users in Hong Kong. The attackers exploited a XNU privilege escalation vulnerability (CVE-2021-30869) unpatched in macOS Catalina

The watering hole campaign targeted websites of a media outlet and important pro-democracy labor and political group. The researchers discovered that attackers deployed on the sites hosted two iframes that were used to serve iOS and macOS exploits to the visitors.

The experts believe that the attack was orchestrated by a nation-state actor, but did not attribute the campaign to a specific APT group.

ESET also attributed the attacks to an actor with strong technical capabilities. According to Felix Aimé from SEKOIA.IO, one of the sites used by threat actors in the attacks was a fake website targeting Hong Kong activists. 

Researchers also found the legitimate website of Hong Kong, pro-democracy radio station D100 that was compromised to distribute the same exploit before the Google TAG report.

DazzleSpy backdoor watering hole

“The exploit used to gain code execution in the browser is quite complex and had more than 1,000 lines of code once formatted nicely. It’s interesting to note that some code, which suggests the vulnerability could also have been exploited on iOS and even on PAC-enabled (Pointer Authentication Code) devices such as the iPhone XS and newer, has been commented out” reads the analysis published by ESET.

Once exploited the WebKit RCE, threat actors executed the second-state Mach-O binary that exploits the local kernel privilege escalation issue CVE-2021-30869 to run the next stage malware as a root user.

After gaining root, the downloaded payload is loaded and executed in the background on the victim’s machine via launchtl. In the attacks reached by Google, the final payload was tracked as MACMA, while in attacks documented by ESET threat actors employed the DazzleSpy backdoor.

DazzleSpy supports a broad range of features that provide attackers a large set of functionalities to control, and exfiltrate files from, a compromised computer.

Below is a list of supported features:

  • Harvesting system information
  • Executing arbitrary shell commands
  • Dumping iCloud Keychain using a CVE-2019-8526 exploit if the macOS version is lower than 10.14.4
  • Starting or terminating a remote screen session
  • Deleting itself from the machine

“The watering-hole operations this group has pursued show that its targets are likely to be politically active, pro-democracy individuals in Hong Kong. This campaign has similarities with one from 2020 where LightSpy iOS malware (described by TrendMicro and Kaspersky) was distributed the same way, using iframe injection on websites for Hong Kong citizens leading to a WebKit exploit. We cannot confirm at this point whether both campaigns are from the same group, but ESET Research will continue to track and report on similar malicious activities.” concludes the report.

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Pierluigi Paganini

(SecurityAffairs – hacking, macOS backdoor)

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