添加一个额外的安全层从来都不是坏事，但是您可能会发现自己在想从该层中实际获得的好处。今天的超级用户问答文章解释了是什么使得“安全登录”对于好奇的读者来说是安全的。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

图片由马特·比杜尔夫（Flickr）提供。

问题

超级用户读者Nexusfactor想知道什么使安全登录（Ctrl+Alt+Del）安全：

I was reading about enabling Ctrl+Alt+Del (link) as a security measure when logging in. My question is, what exactly is secure about it? What goes on “behind the scenes” that makes it safe from viruses and spyware?

什么使安全登录（Ctrl+Alt+Del）安全？

答案

超级用户贡献者杜德和路易斯为我们找到了答案。首先，伙计：

• “What exactly is secure about it?”

Secure is the fact that Ctrl+Alt+Del is the only key sequence that an operating system will never allow to be redirected. No third party application can respond to this key combination to fake a login window and/or keylog your password for example.

接着是路易斯的回答：

duDE explains how Ctrl+Alt+Del guarantees that a legitimate login desktop will be displayed and how the guarantee benefits security. I will try to answer the second part of your question by explaining that the true safety is provided by the concept of a secure desktop, for which the key combination is just a guarantee of enjoying that security.

In Windows, there are actually different types of desktops. The one that we work in is what we all call the desktop, but has been known by other names such as default, interactive, or application desktop. It is here that any given application can run.

The login screen is actually an entirely different kind of desktop, a secure desktop where only trusted processes are running as SYSTEM. While the key combination will guard against fake login screens, it does not protect against a virus infection that is keylogging all of your keystrokes. The desktop concept adds further protection here by not allowing such a background program access to what is happening on the secure desktop.

You can picture this isolation by remembering what happens to the default desktop when UAC prompts appear. You will notice that UAC prompts are actually in one of these secure desktops.

You can also imagine what the isolation means in terms of security when c***idering a virus that spoofs your mouse pointer. The UAC team blogged about such a scenario:

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