I want to make Linux my main OS. I’ve used Windows for decades. Since Vista or 7, the Windows security model is this, from what I understand:

1. unprivileged programs have limited/no ability to do scary things to your computer. they might be able to read some data, but it’s not going to implant malware in the boot sequence for Windows.
2. if a program wants escalation, it triggers a UAC popup and the user has to accept it. Remote programs cannot accept UAC on a physical person’s behalf. Escalated programs have admin level control and can do the scary things.
3. As with any OS, there may be privilege escalation vulnerabilities that escalate (1) into (2).

I’ve only had Windows malware a few times since Win7, and the entry point was fairly avoidable. (Running a sketchy EXE, and a possible drive-by malware install via an advertisement. I could never prove the latter.)

I have never run a password on my Windows desktops. (edited)

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On any system, physical access is game over. edit: new section. A lot of people in the comments are making some assumptions. I don’t run Windows on laptops. When work provides me with a laptop, they enforce passwords and full disk encryption. That makes sense because they would rather have workers type in a password once per screen lock than than have some random person or competitor get access to their network.

My Windows desktop is always in a house/apartment where I have other measures to determine if people have entered. I also have locks on the doors.

People also seem somewhat ignorant regarding the concept of a threat model. They make the assumption that login password = encryption password and that my machine will contain secrets I want to hide.

In my threat model, anyone with harmful physical access to my desktop is either:

1. Casual burglar looking to sell my items (not steal data)
2. Sophisticated thief looking to drain me financially
3. Government entity with some real or imagined reason to target me

Non-sophisticated on-prem hackers are not in my threat model.

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On Linux, the password is paramount. I’ve tried to understand the security model and I keep failing. Synthesizing from arch wiki

SSH

Equivalent to local physical access as the user. If it’s a sudoers or root account, it can do scary things. Not a threat if ssh is disabled or well secured (password or key pairs).

If a network has a well configured firewall (on the router), it should block ssh requests from outside the network unless the admin specifically wants SSH outside the network.

As with any OS, there may be bugs that allow remote access outside of SSH.

Local login / password prompts to physical users

Without a password, you can’t escalate to root and install new software. Some software, often dealing with hardware (smartctl) requires sudo/root to run.

Encrypted drives

Passwords can decrypt drives if they are encrypted.

Keyrings

Some DEs (KDE) offer a ‘keyring’ that stores passwords. It’s locked/encrypted with a password, usually the same as the login password.

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So what am I missing? Is Windows + UAC + no password secure? What is Linux protecting us from by using passwords?