--- title: How do I test the security of my mobile app? description: Learn how to test mobile app security across authentication, data storage, threat modelling and privacy design with practical real-world guidance. image: https://weareaffective.com/hubfs/learning-centre-images/how-do-i-test-the-security-of-my-mobile-app.webp --- [Skip to content](https://weareaffective.com/learning-centre/how-do-i-test-the-security-of-my-mobile-app#main-content) [![we\_are\_affective\_logo\_200](https://weareaffective.com/hs-fs/hubfs/we_are_affective_logo_200.png?width=175&height=48&name=we_are_affective_logo_200.png "we_are_affective_logo_200")](https://weareaffective.com) - [Home](https://weareaffective.com) - About Us - [Our Story](https://weareaffective.com/about) - [How We Work](https://weareaffective.com/how-we-work) - Our Services - [App Planning & Strategy](https://weareaffective.com/app-planning-strategy) - [App Design](https://weareaffective.com/app-design-agency) - [App UX Design](https://weareaffective.com/app-ux-design) - [App UI Design](https://weareaffective.com/app-ui-design) - [App Technical Architecture](https://weareaffective.com/app-architecture) - [Existing App Audits](https://weareaffective.com/app-audit) - [Case Studies](https://weareaffective.com/case-studies) - [Pricing](https://weareaffective.com/pricing) - [Learning Centre](https://weareaffective.com/learning-centre) - [Get Started](https://weareaffective.com/get-started) Expert Guide Series # How do I test the security of my mobile app? Table of Contents Mobile apps hold a lot. Personal health data, payment details, location history, private messages, and sometimes the kind of information users would not share with anyone face to face. The question of how to test whether that information is actually protected is one we get asked often, and the honest answer is that it depends on what your app does, who uses it, and what you built it without. > A mobile app's security surface is shaped by what it does and who it does it for. Security testing for mobile is a set of decisions you make throughout a build, each one shaped by the specific risks your product creates. A fitness app that shares real-time location data carries different responsibilities than a survey tool for a private audience. An anonymous messaging platform requires safety infrastructure that a hotel booking app will never need. The right question is not whether you have run a security test but whether you have thought carefully about the threat surface your product creates. At We Are Affective, security thinking runs through how we design and build, because the [decisions made early in a product's architecture](https://weareaffective.com/app-architecture-design-we-are-affective) are much harder to undo later. This article walks through the main areas security testing should cover, with the specific approaches we have developed across real products, from anonymous messaging to performance coaching tools to fitness social apps. ## What security testing for mobile apps actually covers Security testing for mobile apps covers more ground than most people assume at the start. The instinct is to think about it as penetration testing, someone trying to break in from the outside. That is part of it, but the majority of vulnerabilities in mobile products come from decisions made inside the build itself, not from external attackers finding clever ways in. The main areas to audit are how users authenticate and what access they get, how data is stored on the device and in the backend, how data moves between the app and any external services, what happens when the app interacts with hardware, how third-party libraries are managed, and whether the permissions the app requests are proportionate to what it actually needs. According to [NowSecure Mobile App Security Research](https://deepstrike.io/blog/mobile-security-statistics), 95% of tested mobile apps fail at least one OWASP MASVS security control, which reflects how easy it is to overlook something when security is treated as a checklist at the end rather than a consideration throughout. The process also has to account for the human side. Users make choices that affect their own security, sharing accounts, ignoring permission prompts, or using the same credentials across multiple services. Testing should model [realistic user behaviour, not just idealised flows](https://weareaffective.com/learning-centre/how-to-structure-a-behavioural-risk-register-before-you-write-a-single-user-stor). A security model that assumes careful, attentive users is not a security model. ## Threat modelling: identifying what you are protecting and from whom Before running any tests, you need to be specific about what you are protecting and from whom. Threat modelling is the process of working that out before anything else. It forces a product team to name their assets, the data and functionality that would cause harm if compromised, and to name their adversaries, the realistic actors who might try to access or misuse those assets. On a fitness social app we worked on, the threat model shifted significantly once we understood who the users actually were. The product was originally built around map-based location sharing so people could find workout partners nearby. Once research showed a high proportion of female users would be using the product, precise location sharing became a serious concern. The adversary was not a sophisticated hacker. The more realistic risk was a bad actor using the app's own intended features to track someone's exact whereabouts. That insight reshaped the whole location feature. A useful threat model covers four things. What data does the app hold or transmit. Who has legitimate access to it and at what level. What would happen if that access were abused. And what is the realistic likelihood and method of that abuse. The answers will vary by product, but the questions are the same every time. ## The design layer your *developers* need We deliver complete UX/UI design and technical specifications your development team can build from immediately. No guesswork, no back and forth, no mid-project surprises. [See how we work](https://weareaffective.com/how-we-work) [Get started](https://weareaffective.com/get-started) No commitment ## Authentication and access control testing Authentication is one of the most common places mobile apps create risk. The choices made here affect security and the experience users have every time they open the product, which makes it worth thinking about carefully from [both directions](https://weareaffective.com/learning-centre/what-makes-users-trust-a-product-enough-to-enter-their-card-details). Social login feels convenient and gets used widely because it removes the need to remember a password. But it introduces a dependency on a third-party platform and shares user data with it. Traditional email and password authentication carries its own risks: weak passwords, credential reuse, and the overhead of forgotten password flows. We advise clients to look at passive login as an alternative. The user enters a phone number or email address and receives a one-time code. There is no password to forget, no password reset flow to build, and no credentials to intercept. It is similarly simple to social login in terms of user effort, but it keeps the authentication entirely internal rather than routing it through a third-party social platform. > Passive login keeps authentication internal and removes the credential interception risk entirely. Access control testing should verify that users can only reach what they are supposed to reach. This includes checking whether authenticated sessions time out appropriately, whether tokens are stored securely, and whether any elevated actions require additional verification before they proceed. Test what happens when a valid session token is replayed after logout. If the server still honours it, the session is not truly closed and the user's account remains exposed. ## Data storage and transmission vulnerabilities How data is stored and moved is where a large number of mobile app breaches originate. Data written to local device storage, cached without encryption, or passed over unencrypted connections can be read by anyone who gains access to the device or sits between the app and its backend. According to [NowSecure Mobile App Risk Intelligence](https://deepstrike.io/blog/mobile-security-statistics), 70% of analysed mobile apps can leak personal data through paths including storage, APIs, logs, and third-party SDKs. #### On-device storage Testing on-device storage means checking what the app writes to the filesystem, shared preferences, or local databases and whether that data is encrypted. Sensitive information including tokens, user identifiers, and any personal details should never be written in plain text. It is also worth auditing what the app logs, because debug logs left active in a production build can expose data that the rest of the app handles carefully. #### Data in transit All communication between the app and its backend should use TLS, and certificate pinning should be considered for any flow involving sensitive data. Testing should verify that the app rejects invalid certificates rather than silently accepting them. A man-in-the-middle interception between an app and its API is one of the more straightforward attacks available to someone on the same network. Audit every third-party SDK in your build. Each one is a potential data transmission path you did not author and may not fully control. Check what each SDK sends, to where, and under what conditions. ## Testing without a traditional API layer Some mobile apps, particularly MVPs built for speed, connect directly to a database service rather than routing requests through a dedicated API. This is a legitimate architectural choice, but it places the full burden of security on the database rules themselves. There is no API acting as a controlled intermediary to validate requests before they reach the data. On a performance coaching survey app we built, we made a deliberate early decision to use Firebase's real-time database directly rather than building a traditional API for the MVP. That kept the build lean and appropriate for a proof of concept, but it meant we had to scrutinise every Firebase security rule very carefully. Any gap in those rules would leave the app or the web response page open to exploitation, because there was no intermediary layer to catch a malformed or malicious request before it reached the database. The security model we designed for that product used a combination of access rules tied to QR code keys. Each survey a presenter created generated a record in Firebase, and audience members accessed their own unique response record via keys embedded in the QR code URL. We then used a cookie and device fingerprinting to restrict write access to one submission per device per survey. This prevented duplicate or fraudulent responses while ensuring respondents could not read anyone else's answers. If you are building without a traditional API, the security rules in your database service are your entire access control layer and need to be treated with the same rigour you would give to API authentication code. ## Hardware integration and simulated environment testing Apps that communicate with physical hardware face a testing challenge that purely software products do not. You need to verify that the app and the device are exchanging the right data, applying settings correctly, and handling disconnection or failure states safely. You also need to do that testing before the hardware is necessarily ready or available in volume. On a baby monitor project we worked on, we needed to test the software integration without relying on the physical device being consistently available. The solution we built was a prototype that ran a web server from the device itself. This let us connect to it directly, inspect its internals, and verify that any setting being applied through the app was correctly reflected in the device's state, while simultaneously controlling the device through the app. That simulated the full communication loop between app and hardware without needing the production device in front of us at every stage of testing. The security considerations in hardware-connected apps extend beyond the app itself. The communication channel between app and device needs to be examined. Who can pair with the device, what commands can be sent, and what happens if an unauthorised device attempts to connect are all part of the threat surface. Build a simulation of your hardware communication layer early in the project. It lets you test security rules and failure states at any point in the build, not just when physical devices are available. ## Location data, privacy boundaries, and security by design Location data is among the most sensitive a mobile app can collect, and it is also one of the most commonly mishandled. Collecting precise coordinates gives a product real utility in many contexts, but it also tells anyone with access to that data exactly where a user is, and often where they live, work, and spend time. #### Designing around the risk On the fitness social app we worked on, the original design showed users' real-time locations on a map so they could find workout partners. When research revealed the user base would include a high proportion of women, showing precise location became a security concern serious enough to fundamentally reshape the feature. The team redesigned it to introduce randomised location offsets, so a potential workout partner's position was shown as a vague area rather than a precise pin. Users could then message each other and review profiles before choosing whether to share their exact location, keeping that disclosure voluntary and informed. #### What the redesign preserved The adjusted design preserved the core value. A user could still see whether someone was close enough to make a meetup feasible. The distance radius gave enough information for a practical decision without exposing a specific address. Designing around the risk did not remove the feature. It made it safer to use, which meant more people would actually use it. Testing location features should include verifying what coordinates are stored, for how long, who can query them, and whether the precision of what is shared matches what the product actually needs. ## User-generated content and in-product safety mechanisms When users can send content to each other, the security question shifts. The risk is no longer only about data being exposed to outsiders. The product itself becomes a potential channel for harm between users, which requires its own infrastructure to manage. On an anonymous messaging app we worked on, the nature of the product created inherent safety concerns from the start. Anonymous communication lowers social inhibition, which is part of the appeal, but it also removes the natural deterrent that stops some people from sending harmful or bullying messages. As we got deeper into examining the security and safety concerns the product created, we added in-product reporting features that allowed users to escalate concerns about inappropriate messages directly to the client's admin team. This gave the platform a mechanism to respond to abuse without exposing users' identities unnecessarily. Safety mechanisms in products that carry user-generated content should be tested for how they perform under realistic conditions. Can a report actually reach someone who can act on it. Is the reporting flow straightforward enough that someone in distress will use it. Are there rate limits on messaging that could slow coordinated harassment. These are product and security questions at the same time. ## Tiered verification and progressive data collection Asking users for data upfront, before they have experienced any value from the product, creates friction and erodes trust. It also often means collecting information the product does not yet need and may never need at that particular moment. A better approach ties data collection to the specific action that requires it. On an auction game product we worked on, we built a [tiered registration model with multiple levels](https://weareaffective.com/learning-centre/how-to-structure-progressive-disclosure-around-a-users-anxiety-not-your-data-mod) of authentication triggered by what a user was trying to do. Watching or favouriting an auction required only a basic account: a name and an email address or phone number. Actually playing a game where real money was involved required a further step: age confirmation and a payment method on file. We only asked for that additional information at the exact moment the product's functionality required it, not as a blanket gate at the start. This approach has security benefits as well as experience benefits. [Collecting only what is needed at each stage](https://weareaffective.com/learning-centre/why-product-owners-should-write-the-users-second-session-before-the-first-one) limits the data held against a user's account in the early phases of their relationship with the product. If a user never progresses beyond watching auctions, the product holds only minimal data about them. | User action | Data required | Verification level | | --- | --- | --- | | Watching or favouriting an auction | Name, email or phone number | Basic account | | Playing a game with real money | Age confirmation, payment method | Elevated verification | ## Beta testing infrastructure and build access control Before a mobile app reaches the public, it goes through internal and external testing phases. How that testing infrastructure is set up affects both the quality of feedback you get and the security of the build during that period. A pre-release build that reaches the wrong people can expose features, data structures, or logic that was not meant to be visible yet. On a social football product we worked on, the App Store Connect account was held by the client since it was registered in their name. We were given admin access to the majority of the account, and we set up three testing groups: one for our team, one for the client, and one external QA group for the client's testers. That structure was designed to control which builds went to which group at each stage of the deployment process. As the project approached launch, the client began bypassing the structure by manually sending already-uploaded builds to whichever group they chose, which caused some problems. Because the account was ultimately theirs, they had the access level to do it and we had limited ability to prevent it. That experience highlighted something worth addressing in any beta testing arrangement. Account ownership, admin access levels, and who can send which builds to which groups should be agreed and documented before the testing phase starts, not resolved ad hoc as pressure builds near launch. 1. Define testing groups before the beta phase begins, with named people in each group. 2. Agree who holds which level of access and what actions require sign-off from both parties. 3. Document the agreed deployment process so there is a shared reference when pressure builds near launch. 4. Audit which builds have gone to which groups if the process breaks down, so you can account for where your code has been. ## When security shapes the experience users actually feel Security decisions do not stay invisible. They surface in the product as [friction, reassurance, or sometimes confusion](https://weareaffective.com/learning-centre/what-makes-users-trust-a-product-enough-to-enter-their-card-details), depending on how they are handled. A login flow that asks for too much too soon creates anxiety. A [permission request with no explanation creates suspicion](https://weareaffective.com/learning-centre/5-things-that-make-the-difference-between-so-so-apps-and-stellar-apps-what-your-). A reporting mechanism buried five layers deep sends a message about how seriously the product takes its users' safety. > Security decisions surface in the product as friction, reassurance, or confusion, depending on how they are designed and explained. The performance coaching survey app is a clear example of security shaping experience positively. We used iOS's built-in libraries to generate QR codes entirely within the presenter's native app, meaning the codes were never stored externally. A code was only ever live and visible in the venue during a live presentation. Once the presenter marked a survey as finished, no further responses could be recorded. For the audience, that created a clean, contained experience with no ambiguity about what they were being asked to submit or who would see it. The security model and the experience model were the same thing. #### Communicating security to users Users do not need a technical explanation of your security architecture, but they do benefit from understanding what the product does with their data and why it asks for what it asks for. A permission request that explains its purpose converts better and builds more trust than one that appears without context. [Designing security communication as part of the product](https://weareaffective.com/learning-centre/how-to-run-a-concept-test-that-doesnt-just-confirm-what-the-team-already-believe) rather than as a legal afterthought produces better outcomes for both trust and compliance. ## Conclusion Security testing for mobile apps is not a single pass at the end of a build. It runs through architectural decisions, feature design, data handling, third-party library choices, and the experience users have from the moment they open the app for the first time. The products we have worked on, from the performance coaching survey tool to the anonymous messaging app to the fitness social platform, each had a different threat surface and required a different approach. What they shared was the need to think about security early, specifically, and in relation to the actual people using the product. The questions worth asking are concrete ones. What data does this feature require and does it actually need all of it. What happens if this access rule is wrong. Who can send what to whom, and what happens when someone misuses that. Where is the line between enough location precision to be useful and enough to be dangerous. Those questions have different answers for every product, which is why a checklist is never quite enough. If you are building something and want to think through the security questions it raises before they become expensive to fix, [let's talk about your app's security design](https://weareaffective.com/get-started). ## Frequently Asked Questions What does mobile app security testing actually cover? Security testing covers a broad range of areas including user authentication, data storage on the device and in the backend, data in transit, hardware interactions, third-party libraries, and app permissions. Most vulnerabilities come from decisions made during the build itself, not from external attackers finding clever ways in. Treating security as a checklist at the end of a project is one of the most common reasons apps fail basic security controls. Do I need to carry out security testing even if my app seems straightforward? Yes, because even simple apps collect data that users expect to be protected, whether that is a name, an email address, or a location. The risks your app creates depend on what it does and who uses it, so a seemingly low-risk product can still have meaningful vulnerabilities. The right approach is to think carefully about your specific threat surface rather than assuming a simple app needs no scrutiny. What is threat modelling and why does it matter? Threat modelling is the process of identifying what data or functionality would cause harm if compromised, and working out who might realistically try to access or misuse it. It should happen before any testing begins, because it shapes every decision that follows. Without it, you risk testing for the wrong things and missing the vulnerabilities that matter most to your actual users. When in the development process should security testing begin? Security thinking should begin at the architecture stage, not at the end of a build. Decisions made early in how a product is structured are much harder to undo later, so waiting until a product is nearly finished significantly increases the cost and complexity of fixing problems. Building security considerations into design and development from the outset is far more effective than retrospective auditing. How does user behaviour affect mobile app security? Users make choices that directly affect their own security, such as sharing accounts, ignoring permission prompts, or reusing the same credentials across multiple services. A security model that assumes careful and attentive users is not a realistic one, so testing should model genuine user behaviour rather than idealised flows. Accounting for how people actually use an app is just as important as testing the technical infrastructure. Is penetration testing the same as mobile app security testing? Penetration testing is one part of security testing, but it is not the whole picture. The majority of vulnerabilities in mobile apps come from internal build decisions rather than from external attackers finding clever ways in. A thorough security review also covers data storage, authentication logic, third-party libraries, permissions, and how data moves between the app and external services. How do I know which permissions my app should request? The permissions an app requests should be proportionate to what it actually needs to function. Requesting access to location, contacts, or the camera without a clear and necessary reason creates unnecessary risk and can erode user trust. Auditing your permissions as part of a security review helps ensure you are only collecting what you genuinely need. How common is it for mobile apps to fail security checks? Research from NowSecure found that 95% of tested mobile apps fail at least one OWASP MASVS security control, which is the widely used standard for mobile app security. This figure reflects how easy it is to overlook something when security is not considered throughout the build process. 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