Following a recent blog post covering the increasingly common use of compiled AppleScripts in malware, I wanted to explore methods to further hide malicious scripts and reduce the chance of detection.

Resource Forks

Typically when compiling AppleScript or JXA with osacompile the resulting compiled script is output to an .scpt file, which can then be executed with osascript or opened in the Script Editor.app by double clicking. Adding the -x argument to osacompile results in an “execute-only” script, which cannot be edited in the Script Editor and can make for a more painful experience when trying to reverse-engineer the payload.

As macOS endpoint controls continue to evolve, adversaries are consistently adapting their TTPs to defeat Apple’s ever-changing security frameworks. Although .dmg files remain a popular initial access vector, the traditional “right-click and open” method has become largely ineffective—especially with the security enhancements introduced in macOS Sequoia.

This analysis delves into some contemporary disk-image malware campaigns, their execution primitives and obfuscation techniques.

The Demise of “Right-Click Open”

The “right-click open” method of bypassing Gatekeeper, while helpful for a long time, has become less useful to attackers. With the advent of macOS Sequoia, Apple significantly tightened the Gatekeeper and notarization requirements. This has made it harder for unsigned or malicious applications to directly execute, even with a user’s explicit attempt to override built-in controls. While this is a positive step for overall security, it has pushed attackers to find new avenues for initial compromise.