Dangerous macOS Backdoor That Steals User Login Credentials Remained Undetected for Years

A macOS backdoor dubbed Calisto remained undetected from the radar of antivirus solutions for years. The malware initially uploaded into virustotal back in 2016 and remains undetected until May 2018.

Security researchers from Kaspersky spotted the macOS malware sample with suspiciously familiar features that include remote login, screen sharing, remote login and hidden root account.

Calisto Distribution & Installation

Calisto installation file is an unsigned DMG image that poses as a Leading Mac security and antivirus software Intego’s security solution for Mac.

Threat actors made the macOS malware appearing more convincing and only the user who already installed the app can spot the difference.

As like any other application it starts the installation with the license agreement and in the next step it asks for the username and password. Once the user inputs the credentials it shows installation failed and asks users a new installation package from the official site.

Calisto’s activity on a computer with SIP-enabled is limited and it failed to modify system files. In the infected machine, it creates a hidden folder.Callisto to store Keychain data, login credentials, network connection details and Google Chrome data.

With SIP disabled machine it performs many other operations that include

Copying itself to /System/Library/ folder
Sets itself to launch automatically on startup
Unmounts and uninstalls its DMG image
Adds itself to Accessibility
Harvests additional information about the system
Enables remote access to the system
Forwards the harvested data to a C&C server

According to researchers, the Calisto backdoor appears to be similar like Backdoor.OSX.Proton which steals user personal data and contents of Keychain.

To defends against Calisto and their analogues, never disable SIP, Updates OS to current version, Run application only from the trusted source and use a reputed Antivirus.

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