macOS Malware XCSSET

A malware known for targeting macOS operating system has been updated once again to add more features to its toolset that allows it to amass and exfiltrate sensitive data stored in a variety of apps, including apps such as Google Chrome and Telegram, as part of further "refinements in its tactics."

XCSSET was uncovered in August 2020, when it was found targeting Mac developers using an unusual means of distribution that involved injecting a malicious payload into Xcode IDE projects that's executed at the time of building project files in Xcode.

The malware comes with numerous capabilities, such as reading and dumping Safari cookies, injecting malicious JavaScript code into various websites, stealing information from applications, such as Notes, WeChat, Skype, Telegram, and encrypting user files.

Earlier this April, XCSSET received an upgrade that enabled the malware authors to target macOS 11 Big Sur as well as Macs running on M1 chipsets by circumventing new security policies instituted by Apple in the latest operating system.

"The malware downloads its own open tool from its C2 server that comes pre-signed with an ad-hoc signature, whereas if it were on macOS versions 10.15 and lower, it would still use the system's built-in open command to run the apps," Trend Micro researchers previously noted.

Now according to a new write-up published the cybersecurity firm on Thursday, it has been discovered that XCSSET runs a malicious AppleScript file to compress the folder containing Telegram data ("~/Library/Group Containers/6N38VWS5BX.ru.keepcoder.Telegram") into a ZIP archive file, before uploading it to a remote server under their control, thus enabling the threat actor to log in using the victim accounts.

With Google Chrome, the malware attempts to steal passwords stored in the web browser — which are in turn encrypted using a master password called "safe storage key" — by tricking the user into granting root privileges via a fraudulent dialog box, abusing the elevated permissions to run an unauthorized shell command to retrieve the master key from the iCloud Keychain, following which the contents are decrypted and transmitted to the server.

Aside from Chrome and Telegram, XCSSET also has the capacity to plunder valuable information from a variety of apps like Evernote, Opera, Skype, WeChat, and Apple's own Contacts and Notes apps by retrieving said data from their respective sandbox directories.

"The discovery of how it can steal information from various apps highlights the degree to which the malware aggressively attempts to steal various kinds of information from affected systems," the researchers said.


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