Senior Software Engineer, Security

  • New York, NY
  • Full-time

Company Description

We believe everyone should be able to participate and thrive in the economy. So we’re building tools that make commerce easier and more accessible to all. We started with a little white credit card reader but haven’t stopped there. Our new reader helps our sellers accept chip cards and NFC payments, and our Cash app lets people pay each other back instantly. We’re empowering the independent electrician to send invoices, setting up the favorite food truck with a delivery option, helping the ice cream shop pay its employees, and giving the burgeoning coffee chain capital for a second, third, and fourth location. Let’s shorten the distance between having an idea and making a living from it. We’re here to help sellers of all sizes start, run, and grow their business—and helping them grow their business is good business for everyone.

Job Description

We work to guarantee the security of every transaction from dip and tap to receipt. Our ultimate goal is to ensure that there is no possible way to use Square insecurely. In the Signals group, we work to fluidly interpret signals from what could be a compromised or hostile environment - the OS and app running our code. We build workflows, both human and machine, to swiftly judge the requests for privilege that come with those signals, and we hunt the malefactor where they work.

An example of this is our work to support and validate PIN-on-Glass, the ability of our apps to receive entry of a customer PIN after an EMV card dip into our reader. This is a hugely constrained and sensitive transaction, controlled previously entirely by the banking industry, into which we were not only able to introduce our low-cost, easy-access product, but to also influence the industry itself and its newest standards.

We look for software engineers who understand both security and the human cost of securing a digital border. We need people who recognize that a false positive is a frustrated customer, a false negative a possible reconnaissance op, and an engineer’s oversight a precious and limited commodity. We cannot succeed without elegant tooling, as well as targeted advice coming out of our machine-learning pipelines.

You will:

Lead and contribute to projects that span the following:

  • Signals processing
  • Security incident review
  • Information flow and efficiency modeling
  • Case management user interfaces and backends
  • Applied machine learning in security contexts
  • Applied cryptography in hardware and software


You have:

  • A background in software engineering with a deep passion for making all things efficient
  • Strong examples of secure and elegant software development on production systems
  • Demonstrated experience developing, deploying, and monitoring systems for managing and scaling security investigations, judgements, and actions

Additional Information

At Square, we value diversity and always treat all employees and job applicants based on merit, qualifications, competence, and talent. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status. We will consider for employment qualified applicants with criminal histories in a manner consistent with the requirements of the San Francisco Fair Chance Ordinance.