In January 2023, T-Mobile found some strange activity. It was linked to one of their internal APIs. When they looked closer, they found a data leak. It had quietly exposed personal information from 37 million people. There was no hacker inside the company. No dangerous virus or tool. Just one API with poor security. That was enough for hackers to get in.
Soon, more stories came out. Trello had a bad API setup that exposed emails of over 15 million users. In Australia, a forgotten API from Optus leaked data of 9 million people. All these cases followed the same pattern: one weak point—one API—was all it took.
At first, these seemed like small tech mistakes. But they turned into big data problems. Every case started with one security gap. In the end, millions of people were hit. These were not rare events—they were signs. In today’s tech world, APIs connect almost everything. They help apps and tools work together. But without strong security and professional API Development and Integration Services, they can quickly become huge risks. Investing in secure API Development and Integration Services ensures your systems stay protected while still enabling smooth connectivity.
In this guide, we’ll show you why API Security is so important. We’ll explain what it is, the top rules to follow, and the biggest threats, like those from OWASP’s API Top 10 list. We’ll also share proven ways to keep your SaaS platform safe. Today, apps are being built faster than ever. API use is also growing fast. So, it’s more important than ever to focus on API Security and good application security. You don’t want to be the next company in the news for a big breach.
What is Application Programming Interface (API) and API Security?
Let’s start with the basics. What is an API? An API is short for Application Programming Interface. It acts like a bridge. It lets two apps or services talk to each other. For example, a CRM tool may use APIs to work with your email service. Or your phone app may use APIs to get data from a server.
In today’s SaaS world, APIs are the glue that connects cloud tools. They are now more important than ever.
One report says around 71% of web traffic comes from APIs. Many SaaS companies treat APIs like their own main products. This shows how much APIs do. They power most of the work behind the scenes.
Since APIs move a lot of data, like private user info or company logic, they are now top targets for attacks. Recent surveys show a big problem. Around 95% of companies had at least one API security issue. And 84% of experts saw a problem with an API in just the past year. Gartner also said that an API breach leaks 10 times more data than other hacks.
With API attacks rising fast, we need strong API Security. This is a big part of app security and web application security. These terms may sound fancy, but they are really just ways to protect your tools and users.
To put it simply, API Security means keeping your APIs safe from harm. It means protecting the data and tools that your APIs share. One source says it like this: “API Security is the work of keeping APIs safe from attacks. Because APIs give access to important software and data, they are now a key target.” So, API Security is now a must-have for app and web app safety plans.
Good API Security protects four things: Confidentiality, Integrity, Availability, and Non-Repudiation. Let’s break that down. Confidentiality means only the right people can see the data. Integrity means no one can change the data in a bad way. Availability means the API keeps working even when busy. And non-repudiation means you can track who did what and when.
When you build an app, you can’t forget about API Security. If you do, your cool new app could turn into a risk. You need to add web application security, right from the start. That way, your app won’t give hackers a way in.
What are the core principles of API Security?
Before we talk about threats and fixes, let’s go over the basics. Every system, including APIs, needs strong rules to stay safe. These rules are the main parts of API security and app security:
Confidentiality
This means keeping secrets safe. Only people who are allowed should see private data. To do this, we must lock data while it moves (like using HTTPS) and also while it’s stored. We also must use strict rules about who can get in. Research says confidentiality means stopping others from seeing data they shouldn’t. In apps and websites, this rule helps users feel safe and builds trust.
Integrity
This means keeping data correct and unchanged. APIs must stop anyone from making changes unless they’re allowed. Tools like checksums or versioning help us check that the data is real and clean. This rule also connects with app security to protect actions in SaaS apps.
Availability
This means APIs must work when needed. They should be strong and ready to handle many users or attacks like DoS. To stay up, APIs must scale and manage traffic well. This helps websites and apps stay online and fast, even when traffic grows.
Non-Repudiation
This means proving who did what. If someone changes data, we need to know who it was. APIs can keep logs of every request and answer. That way, no one can lie later. This is a key rule for both API security and app security.
What are the Types of APIs and Their Security Considerations?
APIs come in many types. Each one works in its own way. And yes, each one has its own risks. So, every API type needs strong API security and app security steps.
REST APIs
These are the most used today. REST APIs use normal web actions like GET and POST. They send data in a format called JSON. They are light and don’t keep session info. Each request brings its own data. REST APIs use HTTPS to protect data as it travels. They also use tokens like JWT or OAuth 2.0 to check users. But REST APIs can face attacks, like someone injecting harmful code. If we don’t clean the inputs, it can be a problem. If we don’t use encryption, others can steal data. This is why we must follow smart steps in app development and web security.
SOAP APIs
These use an older way called XML. SOAP uses something like envelopes to send data. It has built-in security rules like XML encryption and signatures. That makes SOAP good for big or safe jobs. But SOAP is harder to use. XML can be slow and open to special XML attacks, like XXE. SOAP also needs more work and follows strict rules. Because of that, we must use strong API and app security with SOAP APIs.
GraphQL APIs
This is a newer way. It lets users ask for only the data they want. This saves time and work. But it brings new problems. For one, GraphQL lets users see the whole data plan, which hackers might use. Also, users can ask for too much data at once. This can make the server too busy and cause it to crash. So, you must limit how deep or complex a user’s question can be. Also, turn off the settings that show the data plan when you go live. More apps are now using GraphQL. So, we must take extra care to keep APIs and apps safe.
No matter the type, all APIs need some basic safety rules. Always clean and check all user inputs. Always use strong login systems. And always lock the data while it moves across the web. But each type also needs its own extra care. SOAP has XML rules. GraphQL has flexible questions. REST has its own risks, too. So, you must add special rules to the basics.
In short, web and app security must be a part of every step. From the first design to launch and later updates, we must build safety into everything.
What Are Common API Security Threats and Vulnerabilities?
APIs are like doors to your data. But if these doors aren’t secure, attackers can sneak in. Let’s go through them one by one, with simple examples and ways to fix them.
Broken Object-Level Authorization (BOLA)
Imagine you have a locker. Only you should open it. But if someone else can open it just by changing the locker number, that’s a problem. BOLA happens when APIs let users access data they shouldn’t, just by changing an ID. For example, if user A can see user B’s order by changing the order ID in the URL, that’s BOLA. This issue is behind almost 40% of API attacks.
Fix: Always check if the user has permission to access the data. Use strong authentication methods like OAuth 2.0 or JWT. Ensure the user’s ID matches the data they’re trying to access.
Broken Authentication
This happens when APIs don’t verify users properly. Attackers can pretend to be someone else. For instance, if tokens are easy to guess or steal, bad actors can use them to access accounts. A common example is when someone intercepts a session token and takes over an account.
Fix: Use HTTPS/TLS for all communications. Store passwords securely with hashing and salting. Implement multi-factor authentication. Limit login attempts and monitor for unusual activities.
Broken Object Property-Level Authorization
Sometimes, APIs give out more information than needed. This is called excessive data exposure. For example, an API might return a user’s profile along with hidden fields like admin status or hashed passwords. Attackers can exploit this extra data. Similarly, mass assignment occurs when users can set fields they shouldn’t, like making themselves an admin.
Fix: Only return and accept the necessary data. Define which fields users can see or change. Use schemas to whitelist allowed fields and reject unknown ones.
Unrestricted Resource Consumption
If an API doesn’t limit requests, attackers can overload it. This can slow down or crash the system. For example, someone might send many requests to a heavy endpoint, causing a denial-of-service (DoS) attack.
Fix: Set strict limits on requests per user or IP. Throttle repeated queries. Use API gateways or firewalls to enforce quotas. Monitor traffic for unusual spikes.
Broken Function-Level Authorization
This occurs when users can perform actions they shouldn’t. For instance, if a regular user can access admin functions like deleting users, that’s a problem. It’s often due to missing role checks.
Fix: Implement role-based access control. Define which roles can access which endpoints. Always check permissions on every request.
Unrestricted Access to Sensitive Business Flows
Even if endpoints are protected, attackers can exploit the business logic. For example, if a user can request a free sample every 7 days, a bot might automate this to get unlimited samples.
Fix: Set usage policies and verify requests. Add rate limits or captchas on sensitive actions. Monitor for unusual patterns, like rapid repeated actions.
Server-Side Request Forgery (SSRF)
SSRF happens when an API lets users dictate server requests. For example, an image-resize API might fetch a user-provided URL. If not restricted, attackers can make the server access internal resources.
Fix: Don’t allow arbitrary internal URLs. Use whitelists for allowed domains. Validate and sanitize all URL inputs. Ensure the server can’t access internal networks unnecessarily.
Security Misconfiguration
This includes any wrong security settings. Examples are default admin credentials, enabled debug endpoints in production, or open CORS policies. Such misconfigurations are common and dangerous.
Fix: Treat configuration as code. Use secure defaults. Disable unnecessary features. Regularly audit settings. Use automated tools to catch issues like missing TLS or open directories.
Improper Inventory Management
Organizations often have old or forgotten APIs. These “shadow” endpoints might be unpatched or lack security controls. For example, a forgotten API could lead to massive data leaks.
Fix: Maintain an up-to-date inventory of all APIs. Use discovery tools and thorough documentation. When retiring a service, ensure its APIs are fully disabled. Regularly audit network traffic to find undocumented endpoints.
Unsafe Consumption of APIs
This involves insecure use of third-party APIs or mishandling API responses. For instance, a client might bypass authentication by replaying cached data, or a mobile app might hard-code secrets.
Fix: Validate all data from the client side. Don’t rely solely on client enforcement. Use token introspection and server-side session validation. Educate developers on secure API usage.
Other API Threats to Watch Out For
Besides the OWASP Top 10, there are more dangers:
- DoS/DDoS Attacks: Attackers can flood APIs with requests, causing slowdowns or crashes. Use rate limiting and scalable infrastructure to handle spikes.
- Man-in-the-Middle (MITM): Without encryption, data in transit can be intercepted. Always use HTTPS/TLS for all API endpoints.
- Business Logic Flaws: Even if APIs work as intended, attackers can exploit the logic. For example, stacking coupons or triggering race conditions. Regularly review API workflows to spot such issues.
- API Key/Secret Compromise: If API keys or tokens leak, attackers can impersonate clients. Store secrets securely, rotate keys often, and monitor for unusual usage.
What are the Essential API Security Best Practices?
Keeping APIs safe needs many layers. Let’s show you the key steps every team should take to make APIs and apps more secure:
Authentication and Authorization
Use strong tools to check users. For logins, go with OAuth 2.0 or OpenID Connect. Add a two-factor login for extra safety. For one service that is talking to another, use signed tokens like JWT or mutual TLS. Don’t try to make your own login system. Imperva says an API should use strong login tools, like hashed passwords or two-factor authentication. Use a safe permission system like OAuth or JWT to check user roles. Always follow “least privilege.” That means each role should have only the smallest access it needs. Change secrets often. Remove tokens for clients that stop using your API. These steps help protect your APIs and your whole app.
Encryption (HTTPS/TLS)
Always use HTTPS. Make sure every API endpoint uses it, even for internal use. This keeps your data safe while it moves. Without encryption, bad actors can see or change your data. So, use the latest TLS version. Turn off old, unsafe ciphers. Also, encrypt important data stored on your servers. These steps are a must for strong API and app safety.
Rate Limiting and Throttling
Set limits to stop abuse. For example, stop a user from logging in more than a few times per minute. Or set a limit on how many API calls one user can make. High-cost actions should have even tighter rules. Cloudflare says APIs with no limits can be hit with DDoS attacks. Use your API gateway to set these limits. Throttling slows down bad traffic and tells you when something strange is happening. These steps help apps grow safely and keep your API strong.
API Gateway / WAF
Use a gateway or firewall for every API call. A gateway is like a guard. It checks tokens, allows or blocks calls, and adds rate limits. Imperva says gateways sit between clients and your API. They help with many safety tasks in one spot. You can use AWS API Gateway, Azure API Management, or Kong. Add a Web Application Firewall (WAF) too. Make sure it can read and protect API traffic. Some WAFs block only known attacks, so add schema checks too. These tools protect your app and help build safer software.
Strict Input Validation / Schema Enforcement
Always check what users send you. Never trust input. Match each field to a schema. Only accept data that matches your rules. Cloudflare says to accept only traffic that follows your OpenAPI schema. Block the rest. Stop extra fields or wrong data types. Use tools like JSON Schema or auto-generated code to help. These checks block many threats and make your app safer.
Least Privilege and Parameterization
Give the smallest rights needed. Use safe database queries. Use parameterized queries or an ORM. Never put unchecked input in a SQL string. Also, the API should use a database user with limited rights. These habits help cut down risks at every stage of building an app.
Logging and Monitoring
Keep logs of every API call. Write down who did what, when, and from where. Look for odd behavior, like too many calls from one IP. Or many failed login tries. Imperva says failed logins should be tracked to catch threats early. Connect logs to a tool like a SIEM for alerts. Good logs help track what happened and who did it. They’re also great if you need to check back after an attack. Watching closely is key to a safe app.
Security Testing and Vulnerability Scanning
Don’t wait for hackers to find your bugs. Test your APIs often. Use tools like DAST, fuzzers, and static checkers. Add API security tests to your QA flow. Salt says only 7.5% of teams test their APIs well. That must change. Do pen tests on your APIs. Follow OWASP’s API Security Test Guide. Look for the OWASP Top 10 and other common bugs like SQL or XSS issues. Testing is often key to safe apps and APIs.
Secure Design and Coding Practices
Think about safety from the start. Code in safe ways. For example, don’t leave passwords in your code. Don’t share too much in error messages. Turn off debug tools in live apps. Set rules with CORS to control who can use your API. Use good libraries that are safe. Go back and clean up your code often. Follow “shift-left” ideas—train developers to think about threats early. Think like a hacker. Ask: How could someone try to break this? This mindset helps make apps safer for the long run.
API Versioning and Retirement
When you update your API, add a version, like /v1/. This helps you shut down old versions safely. Always remove old APIs that aren’t used anymore. They can be weak spots. Keep docs fresh and clear. This helps you stay clean and avoids old risks sneaking back in.
Data Classification and Data Protection
Know what kind of data your API uses. If your API deals with private info (like names, financial info, or health data), you may need to follow rules like GDPR or HIPAA. Label data and add more protection to sensitive fields. That could mean better encryption, stronger logs, or even extra login steps. Imperva says to label data so only the right people can see it. This helps with safety and legal rules.
Incident Response and Auditing
Be ready for a problem. Make a plan for API hacks. Know how to change keys, cancel tokens, or shut down a service. Practice these steps often. After any alert or breach, check your logs and traffic. Make sure nothing else was hit. Every issue teaches you something. Use what you learn to get better. This is key for keeping strong API safety in real-world apps.
Each of these tips builds on the others. For example, using a gateway, schema checks, and good logs together gives much better safety than using just one. All these steps create a solid wall of protection around your APIs and help you build strong, safe apps that can grow.
How to Implement API Security in a Step-by-Step Approach?
Keeping APIs safe in SaaS apps can feel hard. But don’t worry—a clear plan makes it much easier. Here’s a simple 10-step guide to help you protect your APIs and boost your app’s safety:
Inventory Your APIs
Start by finding and listing every API you use. This includes ones inside your company, ones customers use, and any third-party ones. Studies say most companies have 33% more APIs than they know about. Also, only about 27% know which APIs handle sensitive info.
Use tools that check traffic or logs to find hidden APIs, also called “shadow APIs.” Then, build a list that includes each API’s owner, use, and how sensitive it is. Keep this list up to date. This is the first big step in keeping your APIs and apps safe.
Classify and Assess Risk
Next, figure out what kind of data each API handles. Is it public, private, personal, or financial? Then ask yourself—what could happen if this API gets hacked?
APIs that use private or important data need stronger safety rules. Also, check if you must follow rules like PCI, HIPAA, or SOC2. This helps you focus on what matters most and gives your app better protection.
Define Access Controls (AuthN/AuthZ)
Now it’s time to set up who can access what. Pick a strong login system like OAuth 2.0 or mutual TLS. Use role-based access so each person can only do what they’re allowed to do.
For example, you might have a “read-only” role and an “admin” role. Use two-step login (MFA) for users with more power. Always check user permissions for every request. As Imperva says, OAuth or JWT are smart and safe picks. These steps are key parts of API safety in today’s apps.
Encrypt All Traffic
Make sure all your API traffic is encrypted. Set up TLS on every API—inside and out. Force all traffic to go from HTTP to HTTPS. Check that your security certificates are valid. Also, check third-party ones.
This stops others from reading your data while it moves. Don’t forget to encrypt stored data too, like in your database. Encryption is a must-have for keeping your app and APIs safe.
Implement Rate Limiting and Throttling
Set limits to stop too many requests at once. For example, only allow 5 login tries per minute per IP. Or set a cap on how many times a user can call an API per minute.
Use both user-level and IP-level limits. This blocks brute-force attacks and denial-of-service attacks. Salt Security says open APIs are easy targets. So, these limits aren’t just for speed—they also protect your app.
Deploy an API Gateway or Firewall
Send all API traffic through a gateway or firewall. This tool checks that each request follows the rules. It can also check logins, block bad requests, and limit traffic.
Imperva says gateways act like safety guards at the door. In the cloud, you can use tools like AWS API Gateway or Cloudflare’s API Shield. Gateways also help you log data and stop DDoS attacks. This is super helpful in SaaS apps, where security needs to be strong at every step.
Enforce Schema Validation (Positive Security)
Use your API specs (like OpenAPI or GraphQL) as a rulebook. If a request doesn’t match the rules (wrong fields, wrong types), block it.
This method only allows safe requests and keeps bad ones out. It protects against attacks and stops leaks. Plus, it supports a “zero trust” mindset, which is great for app security.
Enable Detailed Logging & Monitoring
Turn on logging early in the process. Log who logs in, every API request, and every response. Also, log any changes to data.
Then, use tools like SIEM to find anything strange, like traffic spikes or odd errors. As Imperva says, watching for failed logins can show you if someone is trying to break in.
Set up alerts, too. For example, alert your team if there are lots of 401 errors or if one client sends too many requests. Watching and logging all the time helps stop attacks early.
Test Continuously
Security isn’t a one-time job. Keep testing your APIs often. Scan for bugs and try to hack your own APIs. Don’t just test the app’s UI—focus on the APIs.
Use tools to send weird data and look for weak spots. You can also use real-time tools to watch for strange API use. Imperva says ongoing testing is key. Follow the OWASP API Test Guide to help plan your tests. This keeps your security strong even as your app grows.
Train and Iterate
Lastly, teach your team about API safety. Keep your guides and processes up to date. Treat security like a feature—check it every time you add or change an API.
If you find a problem, update your plan. This loop of learning, testing, and improving helps your API security get better over time. And it builds a culture of safety across your whole team.
Conclusion
APIs are the heart of SaaS. They help connect parts, send data, and keep apps running fast. But if not protected, they become easy targets for attacks.
Bad APIs can leak data, break trust, and get you in trouble with the law. We’ve seen real-life examples of this. That’s why strong API security is a must. In this guide, we explained why it matters, showed the biggest threats, and gave clear steps to keep your APIs safe.
API Security isn’t a one-time fix. It takes work across teams. You need the right tools and people who understand the risks. Trying to handle this alone can leave big gaps. And that could open the door to attacks.
Don’t let your app become the next victim. When your API and app security are strong, your business stays safe. Plus, you get an edge over your competitors.
That’s why it’s smart to work with experts. At Linkitsoft, we know the API risks SaaS teams face. We offer tools and help you follow every step in this guide.
We help you find hidden APIs, improve logins, add smart request limits, test for bugs, and watch everything 24/7. With us, your app gets stronger protection and stays ready for any threat.
Don’t wait for an attack to see what’s missing. Good security is more than defense—it’s peace of mind and better business. You’ve read this guide. You know the risks. You know the steps.
Now it’s time to act.
Want the best API protection and to build safer SaaS apps from the start—with strong API Security, solid Web app safety, and smart app design? Let’s get started.
