Segment receives billions of events from thousands of customers that authenticate weekly, mostly using usernames and passwords. It’s common knowledge in the security community that users frequently pick weak passwords and reuse them across sites. Six months ago, we set out to change that by helping customers select stronger passwords and allowing them to protect their Segment account with Multi-Factor Authentication (MFA).

But First, A Backstory

At Segment, we have various sub-teams working diligently to improve our security story. These efforts have provided significant security improvements which are seldom seen by customers. A perfect example of this is our previous blog post, Secure access to 100 AWS accounts, which describes some incredibly impactful work that most customers will never know about.

In an online business, the parts of your security program most customers interact with are your product security features—even though this is just the tip of the security iceberg. 

Some customers will view your compliance certifications, but the foundational areas of your security program will mostly go unnoticed outside of your customers’ vendor security teams. 

To provide the security your customers deserve, you need to have a well-rounded security program. If you’re interested in seeing what that journey looks like from our Chief Information Security Officer, Coleen Coolidge, check out her recent presentation at an OWASP Bay Area meetup on how to build security capabilities at a startup.

Two tenets of our security team are to be part of the overall business’ success, and to partner closely with the rest of engineering. The importance of being part of the overall business’ success is obvious—without Segment there is no Segment Security Team. This translates to making practical security decisions for Segment employees, helping sales and marketing, and always keeping the customer in mind.

Working closely with engineering is important because the cumulative number of design choices, lines of code written, and bugs avoided by engineering is much higher than that of security. Working collaboratively with engineering allows us to learn from each other and help everyone be a better security champion. 

We believe that making good software requires making good security choices, and our security team is here to help the larger Segment team achieve that goal.

Luckily for the security industry, security is becoming an increasingly important part of the software-evaluation process. Security should be something customers have positive experiences with throughout their evaluation of your product. Two areas of opportunity that Segment Security and Engineering recently partnered on are our sign up and authentication workflows. 

Password Strength Guidance

A few years ago NIST released updated guidelines for passwords. Historically, many applications made users select an 8 character password with letters, numbers, and symbols which resulted in an overwhelming number of people picking Password1!. Applications also required regular rotation of passwords, which resulted in Password2!. Some of the new guidelines for passwords include disallowing commonly used passwords, disallowing passwords from previous breaches, and encouraging users to employ a variety of strong password strategies as illustrated in this well-known XKCD comic. To accomplish this, we turned to Dropbox’s zxcvbn module and Troy Hunt’s Have I Been Pwned (HIBP) API.

zxcvbn allows us to meet most of NIST’s password guidelines. Commonly used passwords or those that are easy to guess are scored low, and good password created by a variety of strategies are scored high. However, zxcvbn does not identify when passwords have been part of a known breach, which is why we rely on Have I Been Pwned (don’t worry, we aren’t sending your password outside of Segment and if you’re interested in how this process works it is explained on Troy Hunt’s website—linked above).

As a SaaS company, the sign up process at Segment is extremely important to the user. It sets the stage for a smooth experience. To make sure our design wouldn’t negatively impact signups and would positively impact password strength, we took a few steps to make sure we got things right. If you want your security engineering team to be treated like an engineering team, you need to follow the same principles and processes as software engineering teams. 

For this feature, that meant getting feedback from our activation engineering, product, and design teams early in the process. 

Through a close partnership with these teams, we were able to take my original mockups and turn them into customer-facing feature. 

As you can see in the above images, we block users from selecting any passwords of zxcvbn score 0 or 1, and warn them if they are selecting a password that has previously shown up in a breach. We chose to warn instead of block on breached passwords partially to reduce our reliance on the Have I Been Pwned API, and partially to limit the times a user is blocked during sign up.

Once we had a design and workflow we were all happy with, we released it to all customers completing the change and reset password workflows. These flows are seldom taken compared to sign up, and less risky to change because existing customers are more forgiving to a potentially negative experience.

To verify our changes were having the intended effect, we used our analytics.js module to track changes in password strength. As customers and frequent readers of our blog will know, Segment helps our customers track events and make informed decisions for their customers. While monitoring stats about recently changed passwords, we saw a 30% decrease of breached passwords and an increase in average zxcvbn score from 3 to 3.5, which meant our new UI was having the intended effect.

To make sure our design was pleasing to customers we added the new password UI to our signup flow and displayed it to half of our users as part of a 2 week A/B test. If things went well, we would make it live for everyone, and if it didn’t we’d try a different design. During the first week the signup percentages were the same, and during the second week we actually saw a slightly higher conversion rate on the new password interface. As a result, every customer that signs up now goes through the new user interface and receives guidance on choosing a strong password.

Multi-Factor Authentication (MFA)

Unfortunately, despite our best efforts in helping users pick strong and unique passwords, we know that many will not and those that do would like the added layer of security of a second factor. Several weeks ago we quietly released MFA to all workspaces that do not authenticate via Single Sign-On (MFA is usually handled at the Identity Provider level for SSO users). Everyone now has the option to use Time-based One Time Passwords (TOTP) via an app that can read QR Codes (e.g. Google Authenticator or 1Password), and our U.S. and Canadian customers can use SMS-based codes sent by Authy.

Similar to the development of our new password experience, Security partnered closely with Engineering and Design, and used Segment tracking events to monitor adoption. Once the feature was released, we let customers know it was available using a simple notification.

We also wanted to closely monitor MFA failures. If someone completes the username and password portion of authentication, and then repeatedly fails the MFA code portion it may mean that account password has been compromised by an attacker. If we see this behavior, we want to let our customer know that they should change their password to help prevent the attacker from gaining access to their account. To do this we used Segment’s Personas product. We created a custom audience of users that have failed MFA a certain number of times in a given time period. When a user enters that audience we send them an email.

Using Segment’s own product to deliver a better Segment experience to our customers is a perfect embodiment of the two tenets we talked about earlier. It helps us become more familiar with the product we’re helping defend which makes us more relevant during design reviews and other security engineering efforts. It also identifies new ways that Segment could be used and marketed to our customers which makes the business successful—all while improving our security posture, helping us safeguard the data our customers have entrusted with us. Our product security story may never be complete, but we’re thrilled to have our customers supporting us on this journey of incremental improvement.


A special thanks goes out to Cat and everyone else that helped make these features possible. There are too many to list but you know who you are 🙂