Cybersecurity in Fintech: How to Secure Your App, APIs, and Customer Data

Fintech has rewritten how the world moves money. Mobile banking, instant lending, investment apps, crypto exchanges, and “pay later” products all run on one foundation: software. That software is constantly under attack.

In this guide, we’ll break down what makes cybersecurity in fintech different, the key risks for your apps and APIs, the regulations you must care about, and how practices like penetration testing, vCISO, and structured compliance

preparation help you stay secure and audit-ready.

The unique cybersecurity landscape of the fintech industry

Fintech security is not just “normal” app security with a few extra controls. Several factors make it uniquely challenging:

1. Money is the product

   Fintech platforms are a direct gateway to funds, credit lines, and financial instruments. That makes them a priority target for financially motivated attackers.

2. API-driven, interconnected ecosystems

   Fintech apps are deeply integrated with banks, payment processors, KYC/AML providers, credit bureaus, open banking platforms, and card schemes via APIs. A single weak or misconfigured API endpoint can expose financial data and enable fraud or account takeover.

3. Cloud-native, fast-moving architectures

   Most fintechs are built on cloud infrastructure, microservices, and CI/CD pipelines. This accelerates delivery but also increases the attack surface if security is not embedded into the SDLC.

4. Tight, evolving regulations

   Frameworks such as PCI DSS, PSD2/SCA, SOC 2, ISO 27001, and the EU’s Digital Operational Resilience Act (DORA) impose strict expectations on how you handle data, manage ICT risk, and ensure resilience.

5. Low tolerance for downtime or errors

   For a consumer, your app failing for an hour feels like “my money is not available”. For regulators, an outage or breach is evidence of weak controls. Both are business-critical.

Why cybersecurity in fintech matters for your business and your users

Cybersecurity in fintech is not a cost center; it is a growth and trust enabler.

• Financial sector breaches are expensive. Studies show that breaches in financial services are among the most costly, with average losses per incident in the multi-million dollar range when you factor in legal fees, remediation, regulatory penalties, and customer churn.

• Trust is your main competitive advantage. Users may try your product because it is convenient or cheaper. They stay because they trust it will protect their money and identity. A single breach can undo years of brand building.

• Regulators and partners expect demonstrable control. Banks, payment schemes, and large enterprise customers increasingly require evidence of strong cybersecurity and compliance (PCI DSS, SOC 2, ISO 27001, DORA readiness) before they sign or renew contracts.

• Resilience directly impacts revenue. Ransomware, DDoS attacks, or cloud misconfigurations can halt transactions, trading or lending. Every minute of downtime is lost revenue and a blow to user confidence.

Investing in security is therefore investing in customer retention, partner trust, and long-term valuation.

Key cybersecurity risks in fintech

Fintech companies face “classic” cyber threats, but with financial and regulatory amplification. Some of the most critical risks include:

Identity theft and account takeover (ATO)

Attackers use phishing, malware, SIM swap, or credential stuffing to hijack user accounts and initiate fraudulent payments or withdrawals.

Data breaches and information exposure

A single misconfigured server, unsecured S3 bucket, vulnerable API, or compromised third-party vendor can expose large volumes of financial and personal data, leading to fines and mandatory notifications.

Insecure or abused APIs

APIs are the backbone of fintech. Vulnerabilities in authentication, authorization, rate limiting, and input validation can allow attackers to pull transaction data, manipulate balances, or abuse business logic.

Third-party and supply-chain risks

Fintech ecosystems rely on cloud providers, KYC/AML platforms, analytics tools, messaging gateways, and other SaaS. A weakness in any of these can become your breach.

Fraud, social engineering, and phishing

Humans remain the weakest link. Fraudsters increasingly target customer support, operations teams, or partners rather than purely technical controls.

DDoS, ransomware, and extortion

Attackers may threaten to bring down trading or payment platforms unless a ransom is paid, or exfiltrate data and extort companies by threatening public leaks.

Configuration errors and shadow IT

Rapid delivery, lack of change control, and unmanaged test environments often lead to exposed databases, open admin interfaces, and unmonitored internet-facing services.

What’s most at risk in fintech?

If you are operating or building a fintech product, assume that attackers are after three core assets:

Customer identity and KYC data

• Full name, address, national ID or passport numbers

• Employment and income data

• Risk profiles and credit scores

This information enables identity theft, synthetic identities, and high-value fraud.

Transactional and cardholder data

• Card numbers, PAN, CVV, expiry dates

• Bank account details and payment tokens

• Transaction histories and merchant data

This data triggers PCI DSS obligations and is highly monetizable on underground markets.

Authentication and authorization secrets

• Password hashes and refresh tokens

• API keys, client secrets, and private keys

• One-time passwords (OTP), push notifications, device IDs

If compromised, attackers can “become” your users or your system components.

Trading, risk, and pricing logic

Algorithmic trading strategies, underwriting models, scoring algorithms, and risk rules are intellectual property that competitors and criminals would like to copy or bypass.

Service availability and integrity

Even when no data is stolen, manipulating balances, altering logs, blocking payouts, or degrading performance can cause serious financial and reputational damage.

The compliance frameworks that shape fintech security

Fintech companies operate under a dense web of regulations and standards. Security and compliance cannot be separated.

PCI DSS (Payment Card Industry Data Security Standard)

If you store, process, or transmit cardholder data, PCI DSS is mandatory. It defines the baseline technical and operational requirements to protect payment account data, covering network security, encryption, access control, logging, and testing.

With PCI DSS 4.0, the emphasis has shifted further toward continuous compliance, risk-based controls, and more flexible validation methods — a big change for fintechs operating complex, API-driven environments.

PSD2, Strong Customer Authentication (SCA) and open banking

In the EU/EEA, the revised Payment Services Directive (PSD2) requires Strong Customer Authentication for most payer-initiated electronic transactions and for accessing payment accounts online.

SCA means using at least two independent factors (something the user knows, has, or is), and is typically implemented with multi-factor authentication and 3D Secure for card payments.

For fintechs building on open banking and account-to-account payments, PSD2/SCA drives:

• Secure API design and access control

• Strong identity verification flows

• Traceable consent and auditability

DORA (Digital Operational Resilience Act)

DORA is an EU regulation that became applicable on 17 January 2025. It sets uniform requirements for how financial entities — including many fintech firms and their critical ICT providers — manage ICT risk, respond to incidents, test resilience, and oversee third-party dependencies.

For fintechs, DORA means:

• Formal ICT risk management frameworks

• Regular operational resilience testing (including threat-led penetration testing for some entities)

• Structured incident reporting and lessons-learned

• Detailed registers of outsourced ICT services and concentration risk monitoring

SOC 2, ISO 27001, and NIST frameworks

While not fintech-specific, these are widely demanded by banks, large enterprises, and investors:

• SOC 2 – Auditor-attested controls for Security, Availability, Confidentiality, Processing Integrity, and Privacy. Critical for B2B SaaS and API-first platforms.

• ISO/IEC 27001 – A formal Information Security Management System (ISMS) framework, often used as a global “proof” of mature security.

• NIST CSF / NIST 800-53 – Widely used as reference catalogs for controls and risk-based security programs.

A mature fintech will map controls across these frameworks to avoid duplicate work and create a unified control library.

How to secure fintech apps, APIs, and customer data

Security in fintech is not a single product. It is a coordinated set of practices spanning architecture, identity, data protection, monitoring, and culture.

1. Design a secure-by-default architecture

• Segment critical services and databases from public-facing components.

• Use Zero Trust principles: authenticate and authorize every request, including east-west traffic between microservices.

• Enforce secure configurations for cloud resources (no public storage buckets or open security groups by default).

• Implement strong secrets management (not hard-coded in code or CI pipelines).

2. Strengthen identity, authentication, and access

• Implement multi-factor authentication (MFA) for all users and admins; align customer flows with SCA requirements in relevant jurisdictions.

• Use secure session management and device binding to prevent token replay.

• Apply least-privilege, role-based access control (RBAC) for employees and service accounts.

• Regularly review and revoke dormant accounts and excessive privileges.

3. Make API security a first-class citizen

• Maintain an up-to-date API inventory (including internal, partner, and third-party APIs).

• Enforce strong authentication (OAuth 2.0/OIDC, mTLS) and fine-grained authorization for each API.

• Apply input validation, schema validation, rate limiting, and throttling to prevent abuse and injection attacks.

• Use an API gateway and web application firewall (WAF) for centralized policy enforcement and monitoring.

4. Protect data at rest, in transit, and in use

• Classify data (cardholder data, banking data, PII, logs) and apply controls based on sensitivity.

• Encrypt data at rest using strong, well-managed keys; encrypt all data in transit using modern TLS configurations.

• Consider tokenization or format-preserving encryption for cardholder and bank account data to reduce PCI DSS scope.

• Minimize data retention and implement strict deletion/archiving policies.

5. Build continuous monitoring, detection, and response

• Centralize logs from applications, APIs, infrastructure, and security tools into a SIEM or security data lake.

• Deploy anomaly and behavior-based detection (e.g., UEBA) to spot unusual transactions, logins, or API calls.

• Maintain an incident response plan aligned with regulatory expectations and test it regularly (tabletop exercises, simulations).

• Integrate alerts with on-call processes to ensure 24/7 response capability.

6. Embed security into the SDLC

• Perform threat modeling on new products and major changes.

• Use automated scanning: SAST, DAST, SCA (dependency checking), container image scanning.

• Introduce security gates in CI/CD pipelines to block high-risk changes.

• Educate developers via secure coding training and create security champions in each squad.

Penetration testing, vCISO, and compliance preparation: where they fit

Technical controls are essential, but they must be tested, guided, and mapped to real-world regulations. That is where penetration testing, vCISO, and structured compliance programs come in.

At ESKA Security, we have built our services specifically around the needs of fintech companies and banks. Our team has deep, hands-on experience helping digital banks, payment providers, lending platforms, trading apps, and financial SaaS products launch securely, pass audits, and scale without unpleasant surprises.

To cover the full security lifecycle, we operate three core practices:

• Red Team – senior penetration testers and offensive security engineers focused on real-world attacks against fintech web and mobile apps, APIs, cloud infrastructure, and payment flows. They simulate how attackers would try to abuse your product, bypass business logic, and move money out of the system.

• Blue Team – SOC and detection engineers who design and operate monitoring, threat detection, and incident response around your applications, APIs, and cloud environment. They help you spot attacks early, contain them fast, and meet regulatory expectations for logging and incident handling.

• GRC Team – governance, risk, and compliance experts who translate complex regulatory requirements (PCI DSS, SOC 2, ISO 27001, DORA, PSD2/open banking, GDPR and others) into a clear, realistic roadmap for your business.

Depending on your stage and priorities, you can engage ESKA Security for:

• Penetration testing and Red Team exercises – to test your fintech apps, APIs, mobile clients, and cloud infrastructure against real-world attack scenarios and business logic abuse.

• vCISO and security strategy – virtual CISO services to build and lead your security program, define priorities, and align security with product and growth goals.

• Compliance readiness and audit preparation – structured programs to prepare you for PCI DSS, SOC 2, ISO 27001, DORA and other frameworks, including gap assessments, remediation planning, policies and evidence packages.

• Blue Team / SOC services – continuous monitoring, alert tuning, incident response playbooks, and threat hunting tailored to fintech and banking environments.

This combination of Red Team, Blue Team, and GRC/vCISO expertise ensures that your controls are not only well-designed on paper, but also battle-tested, continuously monitored, and fully aligned with the compliance and resilience expectations of modern regulators and banking partners.