APIs play an increasingly important role in connecting different systems in a mobile-first world and have become a critical component of most applications. In addition to being at the core of your application, APIs are now also a common target for attackers who exploit their lack of visibility into mobile app activity.
In this article, I look at what you need to know about securing your mobile APIs so you can take the necessary steps to protect them from these attacks.
Mobile API Security Defined
Mobile API security applies to all aspects of securing how your APIs access data and integrate with other services outside your system boundary. If attackers can use or manipulate these external integrations directly manually or by attacking how they are triggered within the app itself, they could access your data or other functionality.
Typically, mobile APIs are built and used like traditional web services. They accept requests over the Internet through an HTTP interface using a variety of standard protocols such as REST and SOAP. The simplest method for testing mobile APIs is to generate requests and analyze responses sent back from the server via a test tool.
This way, you can quickly check if the API endpoint was secured properly before exposing it to your app. If an attacker can request data from within the app itself – for example, by triggering a download of all customer records – severe damage could be done without any authentication checks.
Build security into every step of the development process
When developing mobile APIs essential, you should consider security implications from the very early stages of development. While designing and building your APIs, you should consider what data they will need to access and how they will be used and integrated with the rest of the app.
An essential step in this process is ensuring that your APIs can only access the necessary data when triggered from within an app. Any unauthenticated requests cannot be processed.
Any functionality which requires authentication – such as password resets or modifying customer information – should always be handled via a server-side component running outside the app itself.
This way, it doesn’t matter if an attacker discovers them through manual or automated testing because they won’t have access to request authenticated data even if they successfully exploit them using other attacks.
Protect everything – even if it’s outside your app
Mobile APIs play a crucial role in how different systems and apps get connected. Without these bridges, attackers would have no way to access critical data. This means that any system which exposes an API may be targeted by hackers looking for ways to exploit their functionality or, of course, the information they disclose.
Since APIs don’t need to run on the same system as the app using them, this has raised concerns over whether their security can be guaranteed.
Protecting all of these external endpoints is crucial. If attackers gain access through one of them, they would have access to anything linked with this account – either within the mobile app itself or another web service, depending on how you use it.
In some cases where APIs pull data from other resources, such as a weather forecast, they may pose a slight risk because their impact would be restricted to just one service. In this case, security efforts should focus on protecting the app itself to ensure that any functionality which accesses customer information cannot be exploited.
Protect all connected accounts with strong authentication
When authenticating requests sent to your mobile APIs, you should follow the same standards used for user logins – two-factor authentication is becoming increasingly common and necessary for all online systems. This means that every request must contain an identifier for the account sending it and include proof of possession.
Most of the time, these proof methods are handled within apps, so attackers cannot generate valid requests without having access to device details – such as the mobile number or email address linked with an account.
Of course, this kind of authentication only protects requests sent to your APIs. Since attackers can still target vulnerable endpoints, they must be protected the same way as any other web service.
This means that proper request validation should always be used to ensure attackers cannot escape unintended data, even if they successfully authenticate their requests.
Protecting back-end services
Even though your mobile APIs are exposed to the Internet via a different system, it doesn’t mean that protecting them is any less important than securing your main website or other online resources.
Any vulnerabilities in these endpoints could lead to more severe attacks against remote systems running behind the scenes, including databases where customer information is stored or other online services handling payments.
You should never assume that your mobile API’s security will be good enough because these could be just a stepping stone to targeting more valuable assets.
Protecting back-end infrastructure is vital for protecting all systems linked with an account created from your app, including local data stores used by key components such as backup routines or caching engines.
In many cases, this involves the exact steps you would take to ensure any web service is safe from attack, but some differences must be taken into consideration when it comes to mobile APIs:
Ensuring they’re only reachable via the wire and not directly via IP/port combinations to protect each one from external attacks.
Ensuring you keep a detailed audit trail of all requests and responses to make it easy to spot unusual activity during an investigation. This should include common patterns such as network protocols, HTTP headers, and response codes that can flag anything out of the ordinary or allow a certain degree of automation in analyzing log data.
Proper exception handling:
Take care with how you handle any exceptions raised within your mobile APIs because these may give attackers clues about how they’re implemented.
If one endpoint fails to authenticate a request, it shouldn’t simply return a generic error message. This may reveal information about your back-end systems that hackers could use later on, so instead, ensure that no useful information is included.
Plan for the future
Security in a rapidly evolving marketplace must be a priority for any product to ensure that you’re keeping up with changes that could affect your service.
This means making sure your security testing isn’t limited to internal procedures but also involves external specialists from time to time, especially when looking at new features or designing entirely new APIs.
Internal security testing can reveal many unpleasant surprises, but it’s unlikely they’ll find every vulnerability because you’ve already put them into place.
Therefore, external audits are crucial for discovering problems before attackers do and should include penetration tests using both automated scans and manual investigations by experts who know what signs to look out for.
It’s not a case of finding all possible flaws. After all, there would be no point since these would be easy to exploit – but instead identifying any vulnerabilities which can’t or shouldn’t be easily exploited so that they can be patched up as soon as possible.
This process is no different from what you should already do for your main website and other back-end infrastructure. There’s no reason to think that mobile APIs would require anything special for security testing unless perhaps hosting them within a container such as Amazon EC2.
This does mean avoiding using containers created by third parties because these could allow attackers access to anything running inside and could also contain security flaws of their own.
Even switching across from one cloud provider to another should not affect how your application code is tested. This should only focus on how the app behaves, not on the environment it runs within.
You should also plan for the future because you never know what could happen in the years ahead, significantly if providers change their APIs or even go out of business.
This means taking care to maintain your code rather than relying on any third-party systems (such as cloud providers) and working with whatever open-source software is available to lower maintenance costs in terms of both time and money.
It’s far better to invest in making sure your APIs are secure during development rather than trying to fix problems when they inevitably appear later on when it’s more difficult and much more expensive (in every sense) to make any changes.