Security Engineer Intern (Summer 2026)

About Us

At Cloudflare, we are on a mission to help build a better Internet. Today the company runs one of the world’s largest networks that powers millions of websites and other Internet properties for customers ranging from individual bloggers to SMBs to Fortune 500 companies. Cloudflare protects and accelerates any Internet application online without adding hardware, installing software, or changing a line of code. Internet properties powered by Cloudflare all have web traffic routed through its intelligent global network, which gets smarter with every request. As a result, they see significant improvement in performance and a decrease in spam and other attacks. Cloudflare was named to Entrepreneur Magazine’s Top Company Cultures list and ranked among the World’s Most Innovative Companies by Fast Company. 

At Cloudflare, we’re not looking for people who wait for a polished roadmap; we’re looking for the builders who see the cracks in the Internet that everyone else has simply learned to live with. We value candidates who have the instinct to spot a "normalized" problem and the AI-native curiosity to create a solution using the latest tools. Our culture is built on iteration, leveraging AI to ship faster today to make it better tomorrow, while ensuring that every improvement, no matter how small, is shared across the team to lift everyone up. If you’re the type of person who values curiosity over bureaucracy, and that AI is a partner in solving tough problems to keep the Internet moving forward, you’ll fit right in.

Available location(s): Lisbon, Portugal

About Cloudflare's Security Team

Security is at the heart of Cloudflare’s mission to help build a better Internet. Anytime we push code, it automatically affects the millions of Internet properties (powering websites, remote teams, APIs, mobile apps, etc.) running on our global network. Cloudflare's network is one of the largest in the world, spanning over 330 cities in more than 125 countries, and operating within 50 milliseconds of 95% of the Internet-connected population.

Security Engineering spans across the Cyber Defense & Engineering and CloudforceOne Threat Intelligence & Research teams within the Security group under our Chief Security Officer. Security at Cloudflare ensures that this massive flow of traffic remains secure and resilient against evolving threats. While our core engineering teams build the software that handles traffic, our security engineers build the systems that protect it. Technologies we use to defend the Internet include Go, Rust, Python, and C/C++.

About the Internship Program

The ideal Security Engineering intern is passionate about making the Internet a more secure place. You will work alongside experienced security engineers to identify vulnerabilities, harden our infrastructure, and build tools that protect billions of Internet users. We are looking for interns who are curious, proactive, and able to approach problems with a "security-first" mindset. This is a unique opportunity for engineers who want to learn how to defend systems at a scale that few other companies can offer.

What would you do as a Cloudflare intern?

• Ship and deliver security-focused projects over 12-16 weeks with autonomy and support.
• Work cross-functionally with Product, Infrastructure, and Engineering teams to integrate security into every stage of the development lifecycle.
• Work closely with a mentor to guide you through the internship, develop your security expertise, and help with career goals.
• Build your network across the company through our various in and out of office socials, networking programs, Employee Resource Group (ERG) programs, and Activity Groups.
• Present your security project to the entire company at the end of the internship.
• Connect and learn from our executives and leadership team including our co-founders.
• Write for our Cloudflare blog (e.g., documenting a new security tool or a vulnerability research finding) and be featured on Cloudflare.tv sessions.

You can check out our internship blogs to learn more about our program and hear directly from our past interns.

Examples of desirable skills, knowledge and experience

• Education: Currently pursuing a degree in Computer Science, Cybersecurity, Computer Engineering, or a related technical field.
• Security Fundamentals: A solid understanding of the OWASP Top 10, common attack vectors (XSS, SQLi, CSRF), and how to mitigate them.
• Demonstrated critical thinking skills and drive to learn and adapt new technologies.
• Curiosity, empathy and ability to get things done.
• Ability to commit to a minimum 12 week summer internship.
• In office 3-5 days a week in the location of the internship.
• Local to Lisbon; relocation not provided.
• Bonus: Demonstrated passion for security & software development, such as personal projects, open-source contributions, or experience with our developer platform using Cloudflare for Students.

Please note

• We will be hiring interns through the fall and early spring on a rolling basis until all roles are filled.

What Makes Cloudflare Special?

We’re not just a highly ambitious, large-scale technology company. We’re a highly ambitious, large-scale technology company with a soul. Fundamental to our mission to help build a better Internet is protecting the free and open Internet.

Project Galileo: Since 2014, we've equipped more than 2,400 journalism and civil society organizations in 111 countries with powerful tools to defend themselves against attacks that would otherwise censor their work, technology already used by Cloudflare’s enterprise customers--at no cost.

Athenian Project: In 2017, we created the Athenian Project to ensure that state and local governments have the highest level of protection and reliability for free, so that their constituents have access to election information and voter registration. Since the project, we've provided services to more than 425 local government election websites in 33 states.

1.1.1.1: We released 1.1.1.1 to help fix the foundation of the Internet by building a faster, more secure and privacy-centric public DNS resolver. This is available publicly for everyone to use - it is the first consumer-focused service Cloudflare has ever released. Here’s the deal - we don’t store client IP addresses never, ever. We will continue to abide by our privacy commitment and ensure that no user data is sold to advertisers or used to target consumers.

Sound like something you’d like to be a part of? We’d love to hear from you!

This position may require access to information protected under U.S. export control laws, including the U.S. Export Administration Regulations. Please note that any offer of employment may be conditioned on your authorization to receive software or technology controlled under these U.S. export laws without sponsorship for an export license.

Cloudflare is proud to be an equal opportunity employer.  We are committed to providing equal employment opportunity for all people and place great value in both diversity and inclusiveness.  All qualified applicants will be considered for employment without regard to their, or any other person's, perceived or actual race, color, religion, sex, gender, gender identity, gender expression, sexual orientation, national origin, ancestry, citizenship, age, physical or mental disability, medical condition, family care status, or any other basis protected by law. We are an AA/Veterans/Disabled Employer.

Cloudflare provides reasonable accommodations to qualified individuals with disabilities.  Please tell us if you require a reasonable accommodation to apply for a job. Examples of reasonable accommodations include, but are not limited to, changing the application process, providing documents in an alternate format, using a sign language interpreter, or using specialized equipment.  If you require a reasonable accommodation to apply for a job, please contact us via e-mail at hr@cloudflare.com or via mail at 101 Townsend St. San Francisco, CA 94107.