Duo Security – Overview and Target Market

Part of a series of posts related to the cloud security company Duo Security, Inc. I am not affiliated in any way with Duo Security (please read my more extensive disclaimer below), I’m just doing my best to understand their offering.

History and Products

Duo Security is a cyber-security company based out of Ann Arbor, Michigan, founded in 2009 by Dug Song and Jon Oberheide. In August of 2018 they were acquired by Cisco Systems. Duo’s LinkedIn profile makes a pretty clear and concise statement that they’re going to “democratize security” and that their mission is to “protect the mission of our customers by making security simple for everyone.”

Unaltered screenshot of Duo’s Product page as of 04/29/2019

Duo’s product page makes some pretty big claims about what they can do. Their product lineup targets securing apps and data, but what stood out to me is that they say it works from any location using any device for organizations of all sizes. Duo offers a platform called “Trusted Access” that has multiple parts:

  • Multi-Factor Authentication
  • Endpoint Visibility
  • Adaptive Authentication & Policy Enforcement
  • Remote Access & Single Sign-On

I’ll take a good look at what these actually mean for their customers later, but for now it’s clear they aim to secure and authenticate their customers’ systems.

Duo’s Customers – IT Departments Big and Small

It’s also fairly clear you probably wouldn’t deploy the Trusted Access platform’s features on your home WiFi network to enable trusted secure access to your Google Chromecast, as they target enterprises. They have a really nice use cases section on their homepage that shows some of the different verticals they’re after including:

  • Education
  • Federal
  • Healthcare
  • Legal
  • Retail
  • Technology
  • Finance

I took a look at one use case in particular for their customer Etsy, an online retailer of handmade or “vintage” items.

Authentication: not as easy as it looks. Photo by Jason Blackeye on Unsplash

According to the case study, Etsy’s business problem centered around securing administrators’ access to the internal management systems of their site. They use a number of access tools including SSH and internally developed systems.

Etsy cited “single-factor” authentication as a security problem for their organization, a.k.a. authentication with only a username and associated password between the outside world and access to said management systems. Duo quotes Etsy’s Network Security Manager describing Single-Factor Authentication as a “weak-link” to illustrate this issue.

Etsy used Duo’s Multi-Factor Authentication feature to add another factor to the authentication process for administrators accessing internal management systems of the site. There are multiple options for adding a second factor to the authentication process (which I’ll explore later), but Etsy says they used the Duo Mobile app. The app enables “pushing”, or the sending of an authentication request (after entering the correct password) from Duo’s Trusted Access platform to the app on the administrator’s phone. The administrator approves access from her phone, and is allowed in to the internal management system.

Next I’ll take a closer look at the different features the Trusted Access platform offers.

Non-Affiliation Disclaimer:
I am not affiliated, associated, authorized, endorsed by, or in any way officially connected with Duo Security, or any of its subsidiaries or its affiliates. The official Duo Security website can be found at https://duo.com. The name Duo Security as well as related names, marks, emblems and images are registered trademarks of its owners.

Python Primer 3 – Loops and Conditions

This is my third post in a series to quickly introduce Python:

This part is probably the most difficult to understand, but it’s really what makes programming dynamic and powerful. Loops and conditions logic (and most programming logic, actually) resembles the way people think and behave. I’d say a loop is kind of like eating, execute the same “put into mouth” action while in the “hungry” state. Conditions are pretty much the same as anytime you say “if” in your daily life – if snow is on the road, stay home, otherwise (else) go to work.

If Statement

To illustrate iffing in Python, I’m going to use two built-in functions, len() and print(). len() simply gets the length of something and “returns” it (gives it back) to you, in the form of an integer (a number). print() just writes what you give it to the screen. In the interactive shell, print is usually assumed when you press enter but it’s more useful in a script (more on that later). Using the same colors list from the previous post, I’ll get its length and compare it to 2 (because I can) using the greater-than sign “>”, perhaps you remember that one from grade school.

colors = ["red","purple","blue"]
because_i_can = 2
if len(colors) > because_i_can:
    print("I've got lots of colors")
I've got lots of colors

Notice how the print part is indented. Python requires this to let the interpreter know that particular code is “inside” the if statement. Don’t forget the colon after your condition, Python gets mad.

If you change “because_i_can” to 3, they’re now equal and the print code doesn’t run. This is the nature of iffing – only run the code inside if the condition is true.

There’s lots more to if statements, like “elif” which is just another condition you can add to an if statement, and “else” which runs if none of the if conditions ran. You can look those all up on the official documentation, and probably guess their syntax. But the simplest form only uses one “if”. I use it all the time.


There’s really just two basic kinds of loops, “for” and “while”. Their logic is designed to resemble the English words from which their names are derived. For – “for each something in a group of somethings, do something”. While – “while in something is true, do something. Stop when it’s no longer true”. I personally don’t use while very much although it certainly has its use cases. I mostly find myself trying to slap some data around to get it to do what I want, so I use “for” loops quite a bit. I’ll start with that.

colors = ["red","purple","blue"]
for color in colors:
    print("I like "+color)
I like red
I like purple
I like blue

“color” is a temporary variable that is created on-the-fly as you write the for loop, and “colors” is the group of stuff that you want to go through. The cool part is I only had write my print() code once, but it was executed for each color in colors. Let’s combine it with an if statement to make it a little more fun:

my_favorite_color = "purple"
for color in colors:
    if color == my_favorite_color:
        print("Purple is my FAVORITE color.")
        print("I like "+color)
I like red
Purple is my FAVORITE color.
I like blue

A couple of new things here – “==” is used to compare two things and see if they’re equal. I also added an “else” part to my if statement. It runs if the “if” part doesn’t run.

“While” statements are nice if you want to run some code while a certain something is true. I was quite satisfied with my food example above, so we’ll run with that. Let’s say our stomach can fit 3 potatoes in it. We’ll add potatoes to our stomach until there are 3 in there:

potatoes_in_stomach = 0
while potatoes_in_stomach < 3:
    potatoes_in_stomach += 1

“+=” is a handy way to say “add 1 to this variable”. So 1 was added until potatoes_in_stomach was no longer less than 3.

Built-in functions are cool, but next I’ll take a look at how to make a custom function.

Python Primer 2 – Lists and Dictionaries

This is my second post in a series to quickly introduce Python:

Hopefully after the first post we’ve got an idea how to fire up the Python shell, create a variable (a cardboard box) that has some data type – an integer (a number), or a string (a letter or a number, a word, multiple words, multiple lines, whatever you want actually). A quick note about data types – the “type” determines how the data acts. An two integers can be added together like numbers, e.g. 1+1 = 2. But if you have a number inside a string data type, you can’t do mathy stuff. If you do “1”+”1″ you’ll get “11” because they’re strings, and that’s how strings behave.

As it turns out, you can bundle these data types together using things called Lists and Dictionaries. Don’t get discouraged if these make your head hurt at first, it hurt for me too when I first learned about them. And it may be hard to see how or why you might use these things at first, but rest assured they are used extensively.

The List

A list is pretty much what is sounds like. You can get your stuff in the list by referring to its order in the list, thus its called an “ordered” list. Lists start with “[” and end with “]” (called square brackets, or just brackets). List items are separated with commas. Typically you store your list inside a variable, like so:

colors = ["red","purple","blue"]

So if you want to grab just the first item in the list, type “colors”, immediately followed by the list item number enclosed in brackets:


Was thinking I would get ‘red’, but actually everything in computers starts with 0. So colors[0] = ‘red’, colors[1] = ‘purple’, and colors[2] = ‘blue’ (Single and double quotes are interchangeable).

Python has a plethora built-in “functions” that I like to think of as mini-programs. You can get a whole list of them and much more at the official Python Documentation. I only mention this because we’re going to use a built-in function to do something fun. Fun if you’re a nerd, like me.

If you wanted a string like “red” to be upper case, but didn’t want to go to the work of redefining it, you could simply use a string function that already exists for it. Python says we need to use a dot “.” after the string we want to make uppercase. Also since it’s a function and “upper” is its name, put some parentheses after it to tell Python that you want to run (execute) it, because that’s how some people a million years ago decided execution should be notated:


But instead of re-writing the string, we’ll just grab it from the list instead since it’s already there:


The Dictionary

A dictionary is a way of doing a similar thing to a list, but the items aren’t in any particular order. You grab a particular piece of data (Python calls it a “value”) in the dictionary by referencing its “key”, which is just another piece of data. Usually people refer to dictionaries as being a database of key/value pairs, but that is really only useful if you already know how it works.

I’m sure this has been used in many other tutorials, but I think a good example might be of a set of stock market tickers and their associated share prices. The ticker is the key, the price is the value. A dictionary uses (curly) braces at the start and end, each key/value pair use a colon between them, and pairs are separated by commas. Again, it’s usually stored in a variable:

stocks = {'GOOGL':1189.84, 'AAPL':186.79, 'FB':167.68}

If you wanted to grab Google’s price, do the same dance as with a list, but use the key on the left to get the value on the right:


If you want to set a new value for ‘GOOGL’ since it’s price has changed, change it like you would a variable:

stocks['GOOGL'] = 1189.92
{'GOOGL': 1189.92, 'AAPL': 186.79, 'FB': 167.68}

One fun thing you can do using a built-in function is to add a new pair to the dictionary, by “updating” it (lists have a similar “append” function). For the list example I used a function on the string inside the list, here I’m using a function on the dictionary itself, hence “.update()” is attached to “stocks”:

{'GOOGL': 1189.92, 'AAPL': 186.79, 'FB': 167.68, 'NFLX': 359.97}

I hope that’s useful. Next up is loops and conditions.

Python Primer 1

This is my first post in a series to quickly introduce Python:

I use Python a fair amount. Anytime I want to tell the computer to do something really specific that isn’t accomplished easily in some off-the-shelf software, Python is my go-to. There are blogs, books, websites, and others that can explain all the amazing things that this cool programming language can do, but since I foresee using Python to illustrate other concepts that I’m trying to learn and understand, I’m going to try explain what I feel are the most important parts in the fewest amount of words. So on that note, here we go:

Getting Started

Most places start you off with some fancy development software called IDE (Integrated Development Environment) but I don’t really like those and I think it’s important to try the basics first and work up from there.

Microsoft Windows

You’ll want to go to https://www.python.org/downloads/windows/ Just go through the installer and you should be up and running.

Mac (OSX)

For an Apple computer same deal, just go to https://www.python.org/downloads/windows/ and install. OSX comes with Python 2 but not 3, unfortunately, so it has to be added.


If you are using Linux, you probably don’t need to be told how to do this, and listing all the ways to install software on the various major distributions is a waste of cyberspace. I use Ubuntu, it’s already installed.

Fire Up The Shell

The “shell” or command-line is basically just normal Python in slow motion, because we humans type commands slow. Here you can type in commands to the Python “interpreter” one at a time (you can also paste them in for faster results). Python is “interpreted” as opposed to “compiled” (like C++ or Java) because it converts the code you write to machine code when you run your program, instead of doing the conversion beforehand as with compilation. This approach has advantages and disadvantages, places where it’s useful and where it’s not. But the command line feature is great for testing since you can write your code and execute it right there by pressing enter.

On Windows, just search for Python and click on what you find. You’ll be at the right spot if your terminal window looks like mine below. On Mac and Linux pull up a bash terminal type “python3” and you’re off to the races.

Python 3 on Windows

What can you do from here? For starters it’s a great calculator:

Or you can use it to scare your co-workers on Halloween:

But you’ll probably want to do something a little more interesting. For that we’ll need some of the basics.

The Variable

It actually took me quite a while to realize that a variable is just a box in which you put something. Behind the scenes a variable is just some space allocated in memory for whatever data you want to store, but Python handles all of that messy stuff for you since it’s a relatively “high-level” language, meaning a lot of dealing with computer inner-workings like memory addressing and CPU instructions is handled for you so you can focus on getting the computer to do what you want. Not that you should avoid learning about that, but in a lot of situations this high-level approach lets you get things done a lot faster. In any case, just think of a variable as a cardboard box. You can put numbers (Python calls them integers) in a variable. Press enter after you’re done with a line:

x = 1
y = 2
z = 3

x, y, and z are just some variable names I picked that have no meaning, really. Use the “=” sign to put a value in your variable. Now you can reference the names in your code, and not the numbers:

x + y + z

You can re-purpose your variables by reassigning values to them:

x = "The quick brown fox jumps over "
y = "the lazy dog."
x + y
'The quick brown fox jumps over the lazy dog.'

The part between quotes “” is called a “string”, meaning alpha-numeric characters strung together. A string can be just one letter, one word, multiple words, multiple lines, it doesn’t really matter (I’ll quickly mention that strings can use single quotes or double quotes, doesn’t matter which).

But don’t try to add two variables that aren’t the same “data type”, like an integer and a string, because Python gets mad:

y + z
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: must be str, not int

Welcome to the world of errors, you’ll be seeing a lot of those.

Next up is some cool ways to organize your stuff, Python calls them Lists and Dictionaries. See you next time!

Understanding Logic Gates

This post is part of a series in which I am following the structure of J. Clark Scott’s book But How Do It Know? (Affiliate Link – commission supports my knowledge quest). You can check out his website at http://www.buthowdoitknow.com/ (not an affiliate link). It’s written with no assumption of knowledge or background in computers, which has been great for me 😉

What Do Logic Gates Actually Look Like?

A computer is essentially a rat’s nest of fairly straightforward contraptions called logic gates. The two components that make a computer a computer are full of them – the CPU and RAM (See link for my post on how they communicate). They operate using electrical wires (turning them on and off to represent 1’s and 0’s) that serve as “input” (going into the gate) and “output” (coming out of the gate). There are lots of circuit diagrams out there that use symbols, but it’s kind of tough to get a look at what a logic gate might physically look like. The best photo I could find of a real device was actually here on Wikipedia (where all good things come from) on the page for NAND gate. I like it because it juxtaposes the symbol diagram alongside the actual chip. (There was no attribution information for this photo, please let me know if you find it. I’d be more than glad to give credit where it’s due)

YouTuber LPG‘s “redstone” computer.

J. Clark Scott’s book purposefully avoids talking about the physical construction of such devices, as it’s outside of the scope of the discussion of logic. Since you can’t really see anything that actually shows the internal workings of the 7400 chip shown above, perhaps the next best thing is a really amazing YouTube video on a computer constructed inside Minecraft (a computer game focused on building stuff with blocks, in case you’re not familiar). My hat’s off to the creator, I’m in awe of his creation. In any case, suffice it to say that logic gates are constructed by some physical medium using using chemistry and physics that I don’t yet understand. For now, at least, that awesome YouTube video will have to do.

Universal Gates

What struck me in learning about logic gates was that a number of gates are actually just combinations of other gates. There seems to be a bit of confusion out there on various sites regarding what gates are used to construct what gates, but the general consensus seems to be that NAND (negative-AND) and NOR (negative-OR) are the universal building blocks to build other gates, especially ones that are a little easier to understand like AND, OR, and NOT. In any case, most places purport the existence 7 gates (AND, OR, NOT, NAND, NOR, XOR, XNOR), but the best site I found was an article at All About Circuits on logic gates that shows a total of 16 (although some of them aren’t really gates or binary).

The reason why NAND and NOR are used to build everything else seems to be that the are easily built physically. If I understood more about chemistry and physics I could probably give you a more specific reason based on physical and chemical properties, but most descriptions I can find just say that you need to trust that NAND and NOR are built, then the rest are assembled with multiple interconnected NAND and NOR gates. For example, I have an AND implementation using two NAND gates shown below:

This contraption will turn O on only if both A and B are turned on, just like an AND gate.

How Does It All Fit Together?

Another shameless plug for J. Clark Scott’s book But How Do It Know? (Affiliate Link – commission supports my knowledge quest) because he does a really good job explaining how you would put these gates together to store 8 bits, which is also called a byte. Typically the register size is the size of the CPU’s computational “width”. Nowadays most CPU’s 64 bit, so their registers would be 64 bit as well, although in some cases there may be smaller ones. This tutorial on howstuffworks.com also does a good job explaining registers (didn’t like the section on the gates themselves though, heads up), and uses some terminology that you’ll definitely come across looking at logic gates, such as flip-flop and feedback. Storing a collection of on or off bits into a collection of fancily interconnected logic gates using a “set” wire as input allows you to store the state of the bits when the set wire was activated. Another wire, called “enable” allows you to access or read the bits. Such a collection is called a register, allows you to write bytes and read bytes. Amazing.

You’ll see registers all over the place, usually with a word or words before it to specify what its purpose is, such as Memory Address Register that says you want to access a certain address in memory and transfer the contents stored there (also in a register, called a Memory Data Register) to the CPU, where it will likely store said contents temporarily in a CPU register. All of the actions I have described are executed using combinations these gates, using voltage rising and falling as signalling to represent 1’s and 0’s across the wires. Some of the circuit diagrams and logical collections of gates in modern boards, memory and CPU’s can be intimidating, but I just try remember back to how simple the gates themselves are, and it makes me feel better.

3 Ways the CPU and RAM Communicate

This post is part of a series in which I am following the structure of J. Clark Scott’s book But How Do It Know? (Affiliate Link – commission supports my knowledge quest). You can check out his website at http://www.buthowdoitknow.com/ (not an affiliate link). It’s written with no assumption of knowledge or background, which has been great for me 😉

CPU/RAM Communication – An Elevator Pitch

The CPU and RAM of a computer communicate using system of wires, called a bus. This bus usually has three parts, the address bus, the control bus, and the data bus. Since RAM holds data, and CPU performs some action (processing) on the data, the CPU first sends and address to RAM by turning on (I use “lighting”) wires to indicate (in binary) an address number. It then uses the control bus whether it’s reading from, or writing to, RAM. Finally, if it’s reading from, RAM will send the data across the data bus. If it’s writing to RAM, the CPU sends processed data back to RAM using the same data bus.

A Cook in the Kitchen

I see quite a few explanations made on the relationship between CPU and RAM, usually they are likened to the human brain. I suppose that works, but what helped me understand the basics of this communication was thinking of a cook retrieving and following recipes in the kitchen. It’s an OK analogy, although you probably wouldn’t store food in a cook book. So pretend this cook’s cookbook is really magical.

  1. Get Recipe -> Address Bus.
  2. Read Recipe or Store Food -> Control Bus
  3. Follow Recipe or Place Food in Cookbook (magic) -> Data Bus

The cook will follow the basic 3 steps above. First she finds the Scrambled Eggs recipe by its name (they’re in alphabetical order, of course). Then she decides whether she wants to read the recipe, or store some eggs she just made according to the recipe. In this case, she’ll read it. Finally, she follows the recipe and makes Scrambled Eggs.

In my diagram of a simple CPU, the buses are arbitrarily 2 bits wide and the number of address slots in RAM are 4, mostly because I ran out of room and 4 seemed like a nice easy number. In reality, you would have many, many more slots and bus wires.

1. Address Bus

The CPU first sends an address to RAM using the address bus wires. Each wire represents a bit (a 1 or a 0). In this example there are 2 of them, for a total of 4 possible addresses (00, 01, 10, and 11). If the CPU wants the contents of RAM address 2, it would light up the first wire and keep the second dark to represent 10, or 2 in binary. RAM would send the letter “Picked”, as requested, across the data bus if the Enable wire is lit. Or if the set wire were lit, data would be written to RAM’s data in the 3 slot, perhaps something like “A Peck”.

2. Control Bus

This controls receiving and sending. Enable means “receiving”, set means “sending”. You can also think of this as read or write. In my simple CPU above, lighting the enable wire transfers data from RAM to CPU, lighting the set wire writes data already processed by the CPU to RAM.

3. Data Bus

This is where all the goods are stored in binary. I just picked some funny words to represent data because it seemed like a nice way to illustrate the point, but the data could be anything. Every kind of data out there has some interesting way of encoding it. For example, letters use a system called ASCII or Unicode to translate letters to binary. Pictures use a variety of formatting, like JPEG or PNG, etc. But it’s all binary in a computer.