People are The Weakest Link In Security?

Despite the title, end users are rarely the weak link in security. We often make impossible demands of them. For example, we want them to magically know things which we do not tell them.

Today’s example: in many browsers, this site will display as “” Go ahead. Explore that for a minute, and see if you can find evidence that it’s not. What I see when I visit is:

URL bar showing

When I visit the site, I see it’s a secure site. I click on the word secure, I see this:


But it’s really, which is a Puncycode URL. Punycode is way to encode other languages so they display properly. That’s good. What’s not good is that there’s no way to know that those are not the letters you think they are. Xudong Zheng explains the problem, in more depth, and writes about how to address it in the short term:

A simple way to limit the damage from bugs such as this is to always use a password manager. In general, users must be very careful and pay attention to the URL when entering personal information. I hope Firefox will consider implementing a fix to this problem since this can cause serious confusion even for those who are extremely mindful of phishing.

I appreciate Xudong taking the time to suggest a fix. And I don’t think the right fix is that we can expect everyone to use a password manager.

When threat modeling, I talk about this as the interplay between threats and mitigations: threats should be mitigated and there’s a threat that any given mitigation can be bypassed. When dealing with people, there’s a simple test product security engineering can use. If you cannot write down the steps that a person must take to be secure, you have a serious problem. If you cannot write that list on a whiteboard, you have a serious problem. I’m not suggesting that there’s an easy or obvious fix to this. But I am suggesting that as long as browser makers are telling their users that looking at the URL bar is a security measure, they have to make that security measure resist attacks.

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