Security threats are the forever top-of-the-list challenges for companies. So, it’s no surprise that investments in that area are growing. However, it’s also no surprise that hackers are adapting quickly. And their new favorite victim is APIs. In fact, just in the last year, 99% of organizations experienced API security troubles.
Why did these tiny communicators become blackhats’ sweet spot? It’s really simple. APIs are extremely prevalent. Most web traffic now flows through them. On average, companies use 131 third-party APIs. Yet, only around 20% can successfully detect attacks at the API level. And so, we’re left with a huge gap in necessary protection measures. That’s why today, we’ll be focusing on how to improve your API security testing.
An incredible thing about APIs is that they are tiny but mighty, connecting your app with other systems and services. But that’s also scary. Because one flaw in these lining elements can cause a lot of damage.
Companies can be fined for data exposure. And we’re not talking about a “slap on the wrist penalty”. For example, T-Mobile was to pay nearly $16 million after tens of millions of customer accounts were exposed. Even bigger numbers can appear when laws like GDPR or HIPAA are involved.
Organizations may face lawsuits from affected customers, partners, or shareholders. Then, you’re not just losing money. You’re wasting time as well. Because legal defense can take months, if not years. For example, T-Mobile agreed to a $350 million settlement in a class-action lawsuit. The firm really should have paid more attention to its API testing services.
Expenses will continue to pile up post-breach, too. Companies often provide identity protection services or direct financial compensation to affected users. And that can last for years. To illustrate, in the aftermath of the famous Equifax breach of 2017, the firm had to pay up to $425 million to affected customers.
What’s more, after an incident occurs, you’ll have to invest in proper remedies. Security audits, infrastructure updates, and additional security testing for APIs will be the minimum. Akamai’s report shows that the average cost of an API security breach is around $600,000 in the US and over $400,000 in the EU.
We can’t forget about the indirect expenses either.
If private data is exposed, a public outcry is almost inevitable. For example, the overly permissive nature of Facebook’s Graph API led to users boycotting the app and deleting their accounts. So, lacking API security testing services might just lead to:
To sum it up, it’s better to invest in high-grade cybersecurity services now than lose thousands or millions of dollars later.
You’re bound to run into a few more challenges when it comes to APIs. Depending on your sector, compliance requirements and fines for non-adherance range dramatically.
Of course, there are cases where fines just go through the roof. That depends on the severity of non-compliance or breach and company size. But just as an example, Meta was to pay €1.2 billion for transferring European users’ personal data to the US without adequate protections.
So, when it comes to security, you need to focus on adequate testing and compliance equally.
It’s time to step aside from the frankly nerve-wracking opening section. Here, we begin with our API security testing guide designed to advance your defenses. If you need a quick refresher on what application programming interfaces are, check out our brief handbook—API testing introduction. For now, we continue.
First, we need to remember that a working API isn’t necessarily a secure API. Imagine a spoon with a flamethrower attached to it. You can still eat soup. But you wouldn’t feel very safe doing it. That’s why functional testing isn’t enough.
Functional tests determine whether your API does what it should:
And security testing looks at how it does what it should in terms of data protection and resilience:
So, API security testing is the process of checking your APIs to make sure they don’t expose data or function in unsafe ways.
Fortunately, you don’t have to start from scratch or reinvent the wheel with API testing. Your niche, industry, and applicable regulations already serve as a guide regarding what to focus on. You can also turn to resources that analyze the most prevalent API threats. Let’s take a look at OWASP’s version.
OWASP Top 10 API Security Risks highlights the following issues as the most common/critical:
They may seem pretty straightforward. But they may not be as easy to fix. How effectively you can handle API vulnerabilities greatly depends on the maturity of your quality processes and team skills. So, before API security testing, you should focus on teaming up with experienced specialists.
There are many ways to approach API security testing. In this section, we’d like to focus on what you should definitely include in your process without trying to restrict your team. Keep in mind that, here, we’re centering on in-depth, manual assessments. They offer the most detailed inspections, which are critical in the current cyber resilience space.
First, you need to find out what the API exposes. Identify all available functions, how they’re called, and what kind of information they return. Here, it’s common to study app behavior or monitor network traffic to uncover hidden or undocumented parts of the API. This helps create a full picture of what could potentially be attacked.
This phase checks how the API controls who can access what. You need to make sure that users have to prove who they are and that they only get access to the parts of the system they’re allowed to use. Your team should also check whether it’s possible to get around these controls or gain access to someone else’s data.
Here, look at how the API handles the data it receives. If the system doesn’t check inputs carefully, it might be tricked into running harmful commands or revealing information. The goal is to see if someone could send unusual or risky data that the API fails to block.
This step focuses on how the API behaves in real-world usage. Look for ways to misuse its features, like skipping steps in a process, repeating actions too quickly, or triggering errors that create unfair advantages. Don’t forget to test whether the API can limit repeated requests to avoid being overwhelmed.
Next, ensure that the API handles sensitive information responsibly. Check if data is properly secured when sent or stored. And make sure personal or confidential information can’t be accidentally exposed. Lastly, pay enough attention to how well the system protects user privacy.
Remember that different app types introduce unique API vulnerabilities. For example, in web API security testing, the goal is to check for risks like:
In mobile API security testing, you’d focus on issues such as:
Each platform brings its own security concerns that need to be tested in context. And while on the subject of context, we should mention REST API security testing. Though the process doesn’t differ much, there are some aspects to consider.
REST APIs don’t keep track of user sessions or past activity. Each request is handled on its own, with no memory of what came before. That means the client (e.g., a mobile app) must send all required information, such as authentication tokens or user IDs, with every request.
For security testing, this means checking that:
Because of REST APIs’ reliance on HTTP methods, you need to make sure that actions (GET, POST, DELETE, PUT) are used correctly. For instance:
REST APIs often use predictable URLs, like /users/1 or /orders/99. This makes it easier for attackers to guess or modify URLs to access other users’ data. That’s why you should focus on checking if unauthorized access is possible.
Sometimes APIs return more data than needed. A response might include personal details or internal system info by mistake. Here, your team ought to ensure that only the right data is shared.
To sum it up, know your product and know your APIs. Follow API security testing best practices but personalize and expand them for your project to get exactly what you want.
An important thing in ensuring adequate security for your APIs is knowing when to use automated or manual testing. The former offers speed and precision. The latter presents flexibility and in-depth exploration. But both need effort and investment. So, let’s review how to apply them for best results and not spend all your budget.
Automation in API testing is becoming a standard. Growing app complexity and the current threat landscape drive it toward becoming a best practice. With automated checks, you can:
Plus, with all the tools available, you can tailor your automation to your project and budget. Below are some examples of the leading API security testing solutions.
OWASP ZAP is a free and open-source tool, fantastic for finding common security flaws. It can snoop on your API traffic and scan for common problems like SQL injection and cross-site scripting. It can even bombard API endpoints with various attack payloads. ZAP works with different API types, including REST and SOAP, and you can plug it into your development process for continuous security checks.
Burp Suite Professional is a popular and highly respected platform. Its proxy feature lets you dive deep into API requests and responses, inspecting and tweaking them. Burp Suite offers advanced features like:
Plus, you can extend its capabilities with add-ons from the BApp Store, giving you access to community-made tools.
Postman lets you create and manage API requests, which you can then use to build basic security tests. For example, you can craft requests to check for broken access control or validate input by sending tricky data. Postman’s scripting abilities allow for more complex test scenarios, like setting up authentication before a request. It takes a bit more manual effort to do full-on security testing. But since most developers use it anyway, it’s a handy first line of defense.
Custom security test suites are often the way to go for certain cases. If you have unique API setups, specific compliance needs, or highly sensitive data, they can be used alongside or instead of off-the-shelf tools. These suites offer unmatched flexibility. They let you precisely mimic real-world attacks, connect with your internal systems, and focus on business logic flaws. They do require more development time and ongoing upkeep. Yet, they also provide the highest level of assurance for your most important APIs.
Automation’s capabilities are vast. But they shouldn’t blind to one simple truth. Even the top API security testing solutions have their limitations.
The point is that the most effective security testing often involves human intuition, creativity, and the ability to think like a blackhat. Automated tools lack this critical element. And it’s essential for uncovering subtle vulnerabilities and novel attack vectors.
While manual checks are superior when it comes to the depth of exploration, we all know of their two main flaws. They’re time-consuming and resource-intensive. That’s why manual testing should be used when it’s actually needed.
An important thing to remember is that the effectiveness of API testing depends on the skills of the person doing it. There’s a big difference between hiring an inexperienced engineer and, say, working with API security testing vendors who specialize in the field.
#1 Professionals have the expertise to find complex business logic flaws and multi-step attack scenarios. They understand the nuances of how an API is supposed to work. So, they can craft creative ways to make it do something it shouldn’t, advancing security.
#2 Experts stay up-to-date with the latest attack techniques, emerging threats, and zero-day exploits. They can anticipate how new vulnerabilities might manifest in your unique API landscape.
#3 Experienced specialists understand your business context, compliance requirements, and the sensitivity of the data handled by your APIs. This allows them to accurately assess the real-world impact of a vulnerability. They can prioritize remediation efforts based on actual business risk, not just technical severity.
#4 Professionals provide clear, detailed, and actionable reports. They include steps to reproduce them and practical recommendations for remediation. Plus, experts present info in an understandable way, bringing teams closer and allowing for better collaboration.
#5 Security specialists offer strategic advice on how to improve your API security, implement best practices, and integrate security into your development lifecycle. They can help you build more secure APIs from the ground up.
#6 Their expertise allows for more accurate vulnerability identification. You can minimize the time wasted on chasing false positives and significantly reduce the risk of missing critical vulnerabilities.
#7 Professionals are typically well-versed in various security standards. They can ensure your APIs meet necessary compliance requirements from the start.
#8 Expert API security testing can save significant costs in the long run. It prevents costly data breaches, reputational damage, and the expensive scramble to fix vulnerabilities after they’ve been exploited.
#9 An external professional team, such as a QA company, provides an unbiased perspective. This fresh set of eyes is free from internal assumptions or blind spots that might exist within your in-house teams.
#10 Working with specialists can also be a valuable learning experience for your crew. They often share insights and best practices, effectively upskilling your internal capabilities.
Briefly, if you think your in-house skills might not secure good defenses for your APIs, consider external help. That’s just not something you’d want to cut corners with. Plus, QA outsource is a quick and cost-effective solution to finding the exact talents you want on your side.
To sum up the above discussion on manual vs automated testing—you should always combine them. Think about it this way. The two approaches offer unique benefits to your API security. So, why settle for only half of them?
That doesn’t mean that you should use manual and automated QA to their maximum. You simply need to apply them in a targeted manner to get the perks that are most valuable for your project.
And if you need guidance on figuring out the best blend of automated and manual QA for your product—we’re here to help.
As you know, testing isn’t a one-time deal. It needs to go on for as long as your product is active to upkeep and advance quality. The same applies to API security. Though it’s a little bit trickier here. Because APIs have become hackers’ sweet spot, you’re not testing application programming interfaces to maintain them. With how things are now, you’re testing your APIs to outrun attackers and find a vulnerability before they do.
In such a first-past-the-post game, testing frequency matters. A lot. That doesn’t mean, however, that you should check your APIs every second. But you definitely should figure out what schedule works for you in terms of skills, budget, and security goals. Here are key aspects to consider in your strategy:
Most organizations go for a blend of comprehensive monthly testing and daily automated scanning. This combo offers a good balance of security coverage and resource efficiency. Yet, it might not work for you. The best solution is always a personalized one. So, you need to choose testing intervals that align with your strategy and capabilities:
Going with only one of the above options isn’t enough. You’ll need to mix and match these API security testing examples so that they effectively cover different threats—from common risks to advanced defenses. And figuring out your strategy isn’t going to be simple.
But there’s some good news. Not all APIs are equal. You won’t have to scrutinize ach and every one of them. That would be inefficient. So, you’ll be going with a risk-based approach to determine testing frequency. This will allow you to focus your efforts where they matter most.
High-risk APIs, ones that are likely to get targeted, should be tested weekly or bi-weekly:
Medium-risk APIs, ones that may not be directly exploitable but still expose sensitive operations, should be tested monthly:
Low-risk APIs, ones that serve static or public data and have limited attack surface, should be tested quarterly:
Prioritizing security testing for APIs is a bit more straightforward. You’ll want to work on your cross-team collaboration to combine every specialist’s perspective (tech and business-oriented). And this amalgamation of expertise will go a long way.
Another aspect that will affect how often you test your APIs is your niche. Different industries face distinct regulatory demands, attack profiles, and traffic patterns. Our team has created a brief API security testing guide for the sectors we cooperated most with. Take a look.
Financial services:
Many institutions still rely on fixed schedules: monthly scans, quarterly reviews, and annual pentests. But this approach often misses fast-moving threats. A better solution is weekly automated scanning and monthly manual testing for critical APIs.
Healthcare:
With strict compliance and high data sensitivity, healthcare APIs need continuous automated scanning backed by monthly comprehensive reviews to stay secure and compliant.
E-commerce:
Traffic surges and seasonal promotions always carry greater risk for APIs. During high-traffic periods, adopt daily automated testing and bi-weekly manual testing. For the rest of the year, monthly manual reviews typically suffice.
SaaS and tech providers:
Fast development cycles mean security must be integrated from the start. That’s why you should apply continuous integration-based scanning paired with sprint-aligned manual testing every two to four weeks.
Keep in mind the above are recommendations based on our QA team’s experience. They aren’t the golden rule. You might need a totally different combination of approaches. And that’s fine. The important thing is that you don’t let “standards” limit your API security testing potential.
Cyberattacks grow more sophisticated. Regulatory pressure intensifies. And customers demand stronger data protection. It’s truly a tough world to live in. Yet, you either adapt or get left behind. There’s no third option. Apart from risk mitigation, making API security one of your priorities shows your commitment to user safety and quality. You can build trust with your customers and set your company apart.
To get there, you should start with mapping out all APIs, assessing risks, and evaluating current testing capabilities. Next, implement basic automated scanning, set up consistent testing practices, and begin team training. And for long-term success, build a mature, continuous API security program integrated into development workflows. Most importantly, don’t stop at “good enough”. Keep improving. Threats can’t get you if you’re far in front of them.
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