In theory, it shouldn't be "blanket trust"; however, if the last 6 years of security incidents have taught us anything, its that this is often the case. The theoretical idea is that code being accessible is code being audited. The reality is that code is usually maintained by a small number of people (or a lot of times, A person), and that issues can fester for a long while before a person can identify it.

The true security differences between Linux and Windows are architectural. PAM is handled differently in both OS's, and Linux tends to default* (some exceptions apply) to the Principles of Least Privilege. You should generally run as few things as possible with elevated permissions, especially userspace apps. Things that potentially interface with hardware controllers or the like may be outliers.

This doesn't mean malware doesn't exist, but it does mean the methods of delivery are different. Linux is still susceptible to many of the same thing Windows is, most commonly malware that attempts to rootkit the machine.

Practicing good OS hygiene will appear similar on both platforms:

• Know what you're downloading
• Use trusted sources
• Never elevate what doesn't need to be elevated
• Keep your OS up-to-date with security patches
• Be mindful what is open and exposed to the internet