XCSSET Sights MacOS

Security researchers have published details about the method used by a strain of macOS malware to steal login information from multiple apps, enabling its operators to steal accounts.

Dubbed XCSSET, the malware keeps evolving and has been targeting macOS developers for more than a year by infecting local Xcode projects. XCSSET collects from infected computers files with sensitive information belonging to certain applications and sends them to C2C Server

One of the targeted apps is Telegram instant messaging software. The malware creates the archive “telegram.applescript” for the “keepcoder.Telegram” folder under the Group Containers directory.

Collecting the Telegram folder allows the hackers to log into the messaging app as the legitimate owner of the account. Copying the stolen folder on another machine with Telegram installed gives the attackers access to the victim’s account.

XCSSET can steal sensitive data this way because normal users can access the Application sandbox directory with read and write permissions.

The threat actor needs to get the Safe Storage Key, which is stored in the user’s keychain as “Chrome Safe Storage.” They use a fake dialog to trick the user into giving administrator privileges to all of the attacker’s operations necessary to get the Safe Storage Key that can decrypt passwords stored in Chrome.

Once decrypted, all the data is sent to the attacker’s command and control server. Similar scripts exist in XCSSET for stealing sensitive data from other apps: Contacts, Evernote, Notes, Opera, Skype, WeChat.

Trend Micro researchers say that the latest version of XCSSET they analyzed also has an updated list of C2 servers and a new “canary” module for cross-site scripting (XSS) injections in the experimental Chrome Canary web browser.

Recent updates of the malware are far from adding significant features, they show that XCSSET is evolving and adapting continuously and targetting the latest macOS version and has been seen in the past leverage a zero-day vulnerability to circumvent protections for full disk access and avoid explicit content from the user.