[Remote] Machine Learning Engineer at Castle


We are looking for someone who loves cyber security, machine learning, and big data, and at the same time appreciates a polished product with beautiful UI and developer-friendly API’s.

You will be building models for verifying users based on their browsing behavior, mouse movements, keystroke dynamics, location changes and device properties – i.e. primarily unsupervised learning and anomaly detection. One of the major challenges is to follow users between desktop and mobile devices, as well as distinguishing between two individuals even though they’re using the same device.

You will also be responsible for architecting our streaming machine learning platform using open-source tools such as Spark, Kafka, Hadoop, Cassandra, etc.

The rest of the product is built primarily in Ruby, Rails, and JavaScript with AngularJS for the client dashboard. We use several storage technologies, including PostgreSQL and Redis. We deploy our Unicorns with Ansible to AWS, manage source and issues on GitHub and plan our daily tasks in Trello. Most importantly we post images of what we have for lunch in #watercooler on Slack. We all work on MacBooks (though most of us come from a Linux background).

Experience with information security or fraud prevention is a big plus.


Castle uses state-of-the-art machine learning to protect web and mobile apps from user account fraud. Users are profiled based on their typing patterns, mouse movements, device characteristics, browsing patterns, and hundreds of other signals. When something suspicious occurs, both the administrator and the user are alerted and can immediately take appropriate action, such as locking the account or having to go through additional verification.


Every line of code that you write will have a great impact. Every suggestion you make that can make our product perform better (ms, ROC, UX or $) has the potential to take the company a huge step forward. You will make a difference!

We’re still a small company staying under the radar. Our vision is to transform the security industry in a way similar to how Stripe revolutionized payments – replacing the traditional sales-driven process with a five minute JavaScript snippet.

When it comes to company culture, building a diverse and inclusive team is at the heart of Castle. We look for voices unlike our own because they help us learn and expand our perspective. It’s depressing to see inequality and exclusion as the defaults of the security industry. Without intentional effort, we will inherit those failings and worsen the problem.


Machine Learning, Big Data, Security


Sweden, Remote OK


$45K – $85K Salary
0.6% – 2.0% Equity


1-10 employees


$360K Last Round in 2015

Please apply at filip@castle.io.

Userbin Sweden AB
Jörgen Ankersgatan 16 C
211 45 Malmö

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