Fintech App Security: 6 Best Practices Every Fintech App Needs

You cannot add fintech app security a week before launch. A payments app, a lending platform or a digital wallet moves money and stores identity data, so an attacker can turn every weak point straight into cash. Fraud rings, credential stuffing bots and malware aimed at banking apps are well organised and patient.

Regulators and partners push the bar higher too. Banks, card schemes and payment providers will ask about your controls well before they let you go live, and more investors now run security due diligence on early-stage fintech startups.

This guide covers the fintech security best practices we treat as a baseline: six core measures, how to secure payments in a fintech startup, what mobile app security and app shielding involve, and the fintech security standards and requirements you are most likely to face.

The main fintech app risks

Before you choose controls, get clear on what you are defending against. For most fintech applications the realistic risks are these:

• Account takeover through stolen or reused passwords, phishing, SIM swapping or session hijacking.
• Payment and transaction fraud, including stolen cards, fake accounts, promo abuse and authorised push payment scams, where the user is tricked into sending money.
• API abuse, such as broken object-level authorisation (one user reading another user's data by changing an ID), weak rate limiting and exposed internal endpoints. The OWASP API Security Top 10 is a good checklist here.
• Attacks on the mobile client: reverse engineering, tampered or repackaged apps, overlay malware, rooted or jailbroken devices and hooking frameworks.
• Data breaches caused by misconfigured cloud storage, secrets leaked in repositories or internal access that is broader than it needs to be.
• Third-party and supply chain risk from compromised dependencies, SDKs and vendors with access to your data.

Each of the six measures below addresses one or more of these risks.

Measure 1: Secure architecture and threat modelling

Security work starts at the design stage. A well-designed system rules out whole classes of vulnerabilities before anyone writes code, and fixing a design flaw later costs far more than avoiding it.

Fintech threat modelling means going through each data flow and asking what could go wrong. Who can call this endpoint? What happens if a request is replayed? Where is card or identity data stored, and which component trusts which? Do this at the start, and again whenever you add a payment flow or a new integration.

• Run an architectural risk assessment during design, before the first release.
• Keep the attack surface small. Expose only the APIs you need and keep admin tools off the public internet.
• Put sensitive services (payments, KYC, ledger) behind an API gateway, with strict authentication between services.
• Where you can, keep card data out of your systems by using a payment provider's hosted fields or tokens. This reduces your PCI DSS scope.
• Design against the standard threats from day one: injection, man-in-the-middle, replay and broken access control.

Measure 2: Strong identity and access management

In a fintech product, identity is the real perimeter. Good customer identity and access management (CIAM) protects users, and strict internal access control protects you from insiders and stolen employee credentials.

• Use multi-factor authentication for logins and for sensitive actions such as adding a payee, changing a phone number or raising limits.
• Prefer phishing-resistant methods. Passkeys and platform biometrics are stronger than SMS codes, which SIM swapping can defeat.
• Give staff role-based access with least privilege, separate admin accounts, and audited access to production data.
• Handle sessions carefully, with short-lived tokens, refresh token rotation, device binding and re-authentication for high-risk operations.
• Add risk-based checks, so a new device, an unusual location or impossible travel triggers step-up authentication.

Measure 3: Data encryption and key management

Financial data must be protected in transit and at rest, and the keys need even more protection than the data.

• Enforce TLS for all traffic, including internal calls between services. On mobile, consider certificate pinning for your own API domains.
• Encrypt databases, backups and file storage at rest.
• Tokenise card numbers and other high-value identifiers, so most of your systems never see the real value.
• Keep keys in a managed key management service or a hardware security module (HSM), rotate them, and separate the people who can use keys from those who administer them.
• Never put secrets in code or mobile app bundles. Use a secrets manager and scan repositories for leaked credentials.
• Collect and keep only the data you need. Data you never store cannot leak.

Measure 4: Secure CI/CD and DevSecOps

Security checks belong in the delivery pipeline, where they run on every change. With DevSecOps, automated checks catch problems while they are still cheap to fix, instead of in a review at the end.

• Static analysis (SAST) and dependency scanning (SCA) on every pull request.
• Secret scanning in repositories and CI logs.
• Container and infrastructure-as-code scanning before deployment.
• Mandatory code review for anything that touches authentication, payments or permissions.
• Signed builds, protected branches and limited access to production deployment.
• Regular penetration tests by an independent team, at least before major releases.

Code written with AI coding assistants is no exception. It needs the same review and scanning as code written by people, and in fintech its authorisation logic deserves a closer look.

Measure 5: Continuous monitoring, fraud detection and incident response

Every set of controls has gaps, so you need to see attacks as they happen and react quickly.

• Centralised, tamper-resistant logs for authentication events, payments and admin actions.
• Real-time fraud monitoring with velocity rules, device fingerprinting and anomaly detection on transactions.
• Alerting with clear on-call ownership, so an alert at night reaches someone who can act on it.
• A written incident response plan covering who decides, how you contain an incident, and how and when you notify partners, regulators and users.
• Tested backups and recovery procedures, which also make you more resilient to ransomware.

Measure 6: Vendor and third-party risk management

Fintech products depend on many external services, including KYC providers, payment processors, banking-as-a-service platforms, analytics and push notification SDKs. Each one adds to your attack surface.

• Assess vendors before you integrate them, and ask for evidence such as SOC 2 Type II reports, ISO/IEC 27001 certification or PCI DSS attestation where relevant.
• Give each integration only the access it needs and keep it isolated from core systems.
• Look hard at third-party mobile SDKs, because they run inside your app with your app's permissions.
• Pin dependency versions, monitor them for vulnerabilities and have a plan for replacing a vendor that becomes a risk.

How to secure payments in a fintech startup

Payments are where the money is, so they get their own checklist. For an early-stage startup, the most effective approach is to shrink what you have to protect.

1. Do not handle raw card data yourself. With your payment provider's hosted payment pages, SDKs or tokenisation, card numbers go straight to the provider, which greatly reduces PCI DSS scope.
2. Use strong customer authentication. In Europe, PSD2 requires it for most electronic payments, typically through 3-D Secure for cards.
3. Make payment APIs idempotent. Idempotency keys prevent double charges when requests are retried, and signed requests with timestamps prevent replay attacks.
4. Verify the signature on every webhook from your payment provider before you update balances or order status.
5. Keep a proper ledger. Double-entry records reconciled against provider reports catch both bugs and fraud.
6. Add limits and fraud rules early: per-user and per-device limits, cooling-off periods for new payees and manual review queues for unusual transactions.

Mobile app security for fintech and app shielding

A mobile fintech app runs on devices you do not control. Assume attackers will download it, decompile it and run it on rooted phones or emulators. Mobile app security for fintech therefore combines secure coding with active protection of the app itself.

Use the OWASP Mobile Application Security project (MASVS and its testing guide) as your baseline. The main points:

• Store tokens only in the platform's secure storage (Keychain on iOS, Keystore on Android), never in plain preferences or files.
• Keep business logic and limits on the server. A rule enforced only in the client is not enforced.
• Use platform attestation to check that requests come from a genuine app on a genuine device: App Attest and DeviceCheck on iOS and the Play Integrity API on Android.
• Where it makes sense, block screenshots and screen recording on screens with sensitive data.

Secure app shielding adds runtime protection on top. It includes code obfuscation, anti-tampering and integrity checks, detection of rooted or jailbroken devices, debuggers, emulators and hooking frameworks, and runtime application self-protection (RASP) that can block or report a compromised session. Shielding cannot make up for insecure design, but for apps that move money it makes attacks considerably more expensive. Decide in advance what the app does in a risky environment: block, limit features, or just flag the session for your fraud system.

If you are building a new product, our mobile app development for startups team builds these controls in from the first sprint, so nothing has to be retrofitted.

Fintech security standards and requirements

Which fintech security standards apply depends on your product, your markets and your licences. These are the most common:

Whatever the framework, the fintech security requirements partners send you look much the same. They want documented policies, MFA everywhere, encryption, access reviews, vulnerability management, logging, incident response, vendor management, and evidence that all of it works. If you build these habits early, certification and bank due diligence hurt a lot less. Until you hire a security lead, an on-demand CTO can own this roadmap. Our fintech software development page describes how we approach compliance-heavy projects.

FAQ

What are the best practices for fintech app security?

Start with threat modelling and secure architecture. Then add strong authentication with MFA, encryption and tokenisation, DevSecOps in the delivery pipeline, continuous monitoring with fraud detection, and vendor risk management. Mobile apps also need secure storage, platform attestation and app shielding.

What are fintech app security solutions?

These are the tools that put the practices in place: identity providers with MFA and passkeys, key management services and HSMs, tokenisation from payment providers, SAST and dependency scanners, fraud detection platforms, logging and SIEM tools, and mobile app shielding or RASP products. A tool only helps when someone configures it and owns it, so pick fewer and use them well.

Which security standards does a fintech startup need?

That depends on what you do. Card payments bring PCI DSS, EU payments bring PSD2 and possibly DORA, personal data brings GDPR, and B2B sales usually lead to SOC 2 or ISO/IEC 27001. Check with legal and compliance advisers for your specific licences and markets.

Is app shielding necessary for a fintech app?

For apps that move money or hold credentials, we strongly recommend it, because it makes reverse engineering, tampering and malware attacks harder. It is an extra layer on top of server-side controls and cannot replace them.

How often should a fintech app be penetration tested?

At least once a year and before major releases or architecture changes, and more often if partners or regulators require it. Automated scanning should run continuously between tests.

Conclusion

A fintech application needs several layers of security: secure design, strong identity, encryption, automated checks in the pipeline, monitoring and control over third parties, plus specific protections for payments and mobile clients. If you get these right early, complying with fintech security standards is mostly a documentation job and does not require a rebuild.

EmphaSoft has been building software since 2010 and has delivered more than 400 projects. If you are planning a fintech product or want a second opinion on the security of an existing one, talk to our team about your architecture and requirements.