In January 2022, a new browser hijacker/adware campaign named ChromeLoader (also known as Choziosi Loader and ChromeBack) was discovered. Despite using simple malicious advertisements, the malware became widespread, potentially leaking data from thousands of users and organizations.

While Windows holds the largest market share on malware, macOS has its fair share of threats that mostly exist in an adware/grayware area. In this post I want to walk through how a Pirrit PKG file installer works. There are lots of more complex threats, but this is a good place to start if you’re just jumping into analysis. If you want to follow along at home, I’m working with this file in MalwareBazaar: https://bazaar.abuse.ch/sample/d39426dbceb54bba51587242f8101184df43cc23af7dc7b364ca2327e28e7825/.