On Security 002: Security Approaches For Personal Social Media Systems

Feb 5 2021 06:30pm

The blogging system deployed in the previous exercise marks our first foray into usable[1] infrastructure. That means it's time to talk about security.

The first security post in this series describes how security overall means appropriately protecting value. In the second post, I proposed a list of values that I believe social media should support, focusing on both capabilities (things the system should enable you to do) and risks (things the system should protect you from). The capabilities I identified center around the ability to use public, semi-public, and private speech via text, photos, sound, videos, and other media. The risks I identified include harassment, misinformation and disinformation, and both small and large-scale threats to privacy. Looking at the list again, I think I also need to add an explicit point about cost, since the operating cost of the system (in time, money, and complexity) affects its availability to different users.

Now that we have a stable idea of what we mean by security and a general idea of the kinds of things we expect this system to do, we can use them to articulate a system of controls that plausibly protect the system as a whole. One of the best resources for this task is a document called NIST Special Publication 800-53 (PDF). This document describes how to match security controls to the intended use[2] of a system--just what we're trying to do now. It describes three different security approaches that systems can use:

  1. Common security approach: In this approach, a single system handles a security control for a number of client systems. You can think of this as a "building security guard" approach. Imagine a condo building in a city. All the occupants of the condo building want the property to be secure, so they hire a security guard in common to sit at the front desk and control building access. In this approach, one system (the security guard role) is responsible for the "building security" function for each individual unit. Every unit depends on the same system.

  2. System-specific security approach: In this approach, each individual system handles its own security. Imagine a neighborhood of the super-rich. Each house is set way back from the street, and there's a big fence around each property. Every house has its own gate with its own security staff controlling access. Every gate guard on the street has basically the same job, but they are only accountable to what the individual homeowner wants.

  3. Hybrid security approach: This approach combines the common and system-specific approaches. In the case of a big condo building, the hybrid security approach would be for a common security guard to control building access, but each resident might have an individual alarm system. The security guard role would be an element of common security, while the alarm systems within the units would be an element of system-specific security.

By using cloud services, we are firmly in the hybrid security approach category. When we use our credentials to put a text file in a bucket, we're relying on the cloud provider to make sure the bucket and its contents are secure against attackers and operational mistakes. However, when we deploy services in the cloud, it's our job to make sure that those services don't introduce or present their own vulnerabilities. AWS (as a representative example of a cloud provider) describes this as the shared responsibility model--they (AWS) are responsible for clearly documenting the security features of their products and we (people who use those services) are responsible for using those security controls in sensible ways.

Since we're talking about services like data storage, let's look at the difference between facebook and the idea of a cloud provider I've been using in this post. A cloud provider is a company you rent services from under some agreement. That agreement spells out what services you're paying for, such as data storage and processing, what it costs, and what the service operator can do. The cloud provider is not allowed to look at your data at all except in special circumstances, such as with a court order or if they notice suspicious activity. This might (correctly) give some people pause, but it is worlds apart from the relationship you have with a social media company like facebook. Facebook may not allow human employees to look around at users' private data, but their entire business model is based on selling access to that data through tools like ad targeting. If everyone with a facebook account managed to switch to their own services hosted on a cloud provider, the cloud provider would not be able[3] to use their data in a comparable way.

So when we talk about a hybrid security approach, we are not talking about letting AWS make decisions about our data. We are talking about using AWS as hired security for resources under our control. We're also acknowledging that we are going to rely on that security for some of our operational needs. We're going to trust that AWS will not let anyone put an object into our bucket unless we've explicitly allowed it. We're going to trust that, as giant companies with huge security budgets and financial reasons to care, cloud providers will tend to do a better job at being security guards than we could on our own[4].

In general, I would suggest that we rely on security systems provided by cloud services in a few different scenarios:

  1. Within specific areas, I may not feel comfortable building certain components from scratch by myself. For instance, I'm strongly considering using an AWS service to handle login. This would likely allow us to have two-factor security for login to our own sites, which would be awesome. I don't think I could build a system as reliably secure, and if I tried I don't think I'd feel comfortable asking others to use it.
  2. Every cloud service includes security controls of one kind or another. An object store like S3 offers access controls for each object. Whenever we are using a service, we will first use the security controls provided for that service, and only implement our own security controls if we need some specific control not included in the built-in ones.
  3. Some of the security controls we want will be about cloud providers. For instance, the billing alert that we set up in a previous post was a security-adjacent control that had to do with AWS itself. In general, we'll trust the cloud providers to make sure those security controls work.

There are also some things that we're going to handle ourselves:

  1. Practice good security: Choose a good password for your AWS account and set up MFA[5]. Do not give out credentials to anyone. Do not run terraform configurations except from people you trust. Don't run any command unless it's from someone you know and trust. Be highly skeptical of anyone claiming to be from Amazon--they don't do house calls. By far, the human factor (you and me) is the biggest source of risk in this whole equation.
  2. Practice least-privilege: each component of the system should only have access that it needs to perform its functions. That means that I am being careful to strictly limit the access given to different components.
  3. Openness and reviewability: Just because I'm being careful doesn't mean I won't mess up, so if you think you've found a flaw please let me know, and thanks for paying attention. All the code involved is in my github repos, linked at the top of this page.

These security posts are kinda hard to write. On one hand, I hope you can tell that I really believe what I'm saying. On the other hand, a lot of the problems we have in the world are because someone like me really believed in something and it turned out to be wrong. The best I can do is to try to show my reasoning for each decision and hope that people will either find it convincing or help me see the problems so I can fix them. Security is very personal; at the end of the day. everyone has to decide for themselves what they value and what they trust.


  1. In this sentence, "usable" means that it's potentially adequate for some users indefinitely, not that it's accessible to all users. The blogging platform in the last exercise is not an end-point; it's a very basic thing that I think a person might call "good enough." My evidence for this claim is that I'm a person. ↩︎

  2. Intended use hides a multitude of sins when we talk about security. Publications like NIST 800-53 trust the security design of a system to fairly represent all the system's stakeholders. In practice, this means that if a system owner wants to do something like track all the users all the time, they can define that capability as an intended use, which then makes it the priority of the security system to protect it, such as by making the data collection efficient and stable and protecting the collected data from adversaries. In my personal and professional opinion, the freedom that average people give to corporations like Google and Facebook to decide on the intended functions of social media systems is the biggest threat that exists in this space. It's precisely why I've chosen the approach of building systems that perform well and cost little when under individual control--so that the definition of "intended functions" with respect to these systems is accountable to individuals as directly as possible. This means that the controls have a better chance of protecting the individuals' values, rather than those of rent-seekers.

    The next question to consider, if we're being honest with ourselves, is: "If the sum of the system that is now facebook (for instance) actually acted in the self-interest of its users, would that be better or worse?" That's a very important and interesting question, and I believe the answer is "it would be better," but it deserves its own blog post. With the big questions like that, I don't really trust anyone who's sure they're right. ↩︎

  3. Here "able" has two separate meanings. First, a cloud provider's customer agreements are dominated by the needs of big customers-- the ones who drop hundreds of thousands on their bill in a month. Those customers--like media companies, pharmaceutical companies, etc. do not mess around when it comes to their confidentiality needs. When a movie studio uses AWS in their editing pipeline, the expectation is that an AWS employee cannot leak the unreleased footage. It would be a disaster for a cloud provider to be seen not to prioritize the confidentiality of its customers' data--it could be a business-ending event. This, much more than any person's assurance, is the kind of security I like to rely on--a case where I have reason to believe that my interests line up with those of a supplier.

    The second meaning of "able" in this context is technical. One of the big advantages that a company like facebook enjoys is that it controls the structure of its data. It has massive databases of highly structured data to which it sells different kinds of access. In a distributed system, even if individuals all collected exactly the same data, it would be stored in a wide variety of much smaller data sets, making it a much bigger logistical challenge to put together even if anyone could get access to it in the first place. ↩︎

  4. This is one of those dangerous arguments that's basically-true but needs to be applied and interpreted carefully. My whole project is in a precarious position, ethically speaking, as long as it's tied exclusively to AWS (see an earlier discussion of this here). There are good reasons for not wanting to have anything at all to do with Amazon as a company, so I don't take lightly the decision to advocate the use of AWS. The reason that I do take that position is because, for now, my priority is to provide system designs in the easiest and most accessible way I can, and my familarity with AWS makes it easiest for me to use as an example system. If this experiment works--if people start to follow along--it will be incumbent on me to demonstrate how these systems can be hosted on any cloud provider that offers a small set of generic services, so that consumers can pressure suppliers to behave ethically.

    Mostly, I don't mean to say that it's as simple as "Amazon does a better job than we could, so we should use AWS." The goal is to design the system in a way that it can be hosted anywhere, but for now AWS satisfies the other criteria best. ↩︎

  5. Unless you want to buy a security key a multifactor authentication app for your phone is probably the most secure second factor you can get--they're very secure. Authy has a good reputation. ↩︎