iOS app security

The reference guide for iOS app security

In this article, I'll try to compile a checklist of things to look for if you want to make sure your app can handle the most common security flaws. The topics that will be discussed are listed below. application programming, data management, data transfer, and application security interfaces.

System API’s Usage

We recommend that you use CryptoKit for all cryptographic API calls in your system and double-check that they are being called correctly. If you don't have to, don't add your own crypto algorithms. Even if you're careful, the review of your app by the App Store could be a problem.

The App's Development: Apps that handle sensitive user data may benefit from a feature that allows them to enter the background and hide the screen (a snapshot of the app is taken at this moment and stored on the device). Check the applicationDidEnterBackground method.

If persistence is enabled, protect the clipboard by clearing it when the application is minimized. Examine the structures UIPasteboardNameFind and UIPasteboardNameGeneral.

If a field is meant to hold sensitive information (passwords, credit cards, etc.), it should say "secure" or be separate from auto-correct.

Confirm that no one is secretly recording your screen or stealing your personal information. To obscure the screen before sharing, use UIScreen.isCaptured() and a subscription to user Did Take Screenshot Notification.

Be aware of the dangers of SQL injection and formatted string injection (the latter should not be an issue in Swift). If you're going to use NSPredicates or a formatted string, make sure to use parameterized strings. To check if a user's email address and password match, use NSPredicate(format: "(email LIKE "(") AND (password LIKE "(user.password)"), nil, but NSPredicate(format: "(email = @) AND (password = @)",, user.password). Before saving to the database or interacting with the server, text can be validated.

Examine the web views to ensure that no unauthorized Java script has been injected.


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Data Management

For more information on the Data Protection API and how to set a protection level before writing, visit NSData.

URL protection and document creation options are available.

The CoreData and Realm databases are.db files that can be extracted and read elsewhere. Before storing information in your database, ensure that it is encrypted.

UserDefaults should not be used to store sensitive data such as access tokens, subscription status, or account information. It is simple to access from outside the app. It is recommended that you migrate to the KeychainService API.

It is recommended that you hash your data with CryptoKit instead of the hashing functions in the Swift Standard Library to avoid a high collision rate.

If you want to be certain about the location of your files on an Apple computer, consult the company's documentation.

Data Transportation

App Transport Security (ATS) must be set up correctly and exceptions must be avoided for data to be moved.

TLS and SSL must be used with caution. Replace all instances of HTTP with HTTPS to make sure that the URL uses HTTPS and that tokens are not sent in the URL itself but in the headers.

Always keep in mind that NSURLSession stores HTTP requests and responses in a cached database file by default (named Cache.db). When working with sensitive data, use ephemeralSessionConfiguration, which does not store cookies or caches. Check the capacity of URLCache, set it to 0, and then use URLCache.shared to turn off the global cache.

App Hardening

You have to decide if you want third-party keyboard support, and you have to turn it off if you think it could be dangerous.

In XCode, run the static analysis report. Keep in mind that debug logs are public by default, so never log sensitive information and use the appropriate tools. Patterns and prints should be avoided.

Obfuscation is a technique for hiding details in a program's source code in order to make it more difficult to decipher in the future. There are numerous external libraries available for this purpose.

To prevent XSS attacks, avoid using URL schemes and verify all URLs.

Despite the fact that jailbreaking is becoming increasingly difficult, a dependable jailbreak detection system is still required. With a jailbroken device, a hacker could figure out how your app works and use that to get to sensitive information.


Clearly, there are numerous factors to consider when addressing your application's security. This list is obviously not exhaustive, but it should serve as a starting point for evaluating the security of your app and determining which factors are most important to you. I hope you found this brief article useful and will refer to it the next time you are tasked with performing an application security audit.

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