API Security: The Complete Guide

By Ben Eaton
Published on October 4, 2022
API Security: The Complete Guide

If your software applications can interact with each other smoothly and flawlessly, nobody but API or Application Programming Security is to be thanked. It is a foundational part of our modern software patterns, which include software patterns like microservices architectures.

As the APIs are commonly used nowadays, and as they make sensitive data and software functions accessible, the attackers look at them as their main target. Looking at the importance of the APIs, one must ensure that they are well protected from any threat or attacks, and the process that helps achieve these security norms is called API security.

API Security serves as a major component of modern web application security. Unfortunately, APIs often suffer from vulnerabilities like broken authorization, authentication, and code injection and may also lack rate limiting. Therefore, organizations must regularly test APIs to identify and address these vulnerabilities utilizing the best security practices.

This article is your guide to APIs and API securities and will make you aware of the best practices to ensure your API's security.

So, let's get started.

Importance of API Security

API security secures the Data transfer that is done through APIs, which mostly happens between servers and clients who are connected over public networks.

Organizations utilize APIs in order to transfer data and connect services. A hacked, compromised, or exposed API can compromise financial information, personal data, or other major sensitive data. Hence, security is a crucial consideration when developing and designing APIs.

APIs are very prone to weakness in the security of the backend systems. Attackers can very easily compromise every API functionality and data if they succeed in compromising the API provider. Malicious requests are another way to exploit APIs, and the APIs not properly protected and coded are most likely to get harmed by these requests.

For instance, an attack of Denial of Service (DOS) can significantly affect APIs performance, or an API endpoint could be taken online due to this attack. Attackers are able to abuse APIs by exceeding the limit of usage or data scraping. The attackers who possess more sophistication can perform operations that are unauthorized by injecting malicious code. With the use of malicious code, attackers are also able to compromise the backend.

As serverless architectures and microservices are getting more popular, most enterprise applications for their basic functionality depend on the API. As a result, API security is a major part of the modern era's information security.

The difference between General Application Security and API security

Let's first look at the major characteristics of general application security:

A moat and castle approach- This traditional approach has a crystal-clear perimeter that controls the points of access. This perimeter refuses or accepts access requests and assumes that the requestors who have entered are amicable.

Mostly static protocol- Incoming requests hold fast to mostly static protocol, allowing the administration to configure a WAF to enforce the protocols.

A web browser is used by the clients- WAF can verify a client's browser environment, and if the environment fails the verification, the WAF assumes that the client is a bot that is using a mindless emulator or browser.

Detecting attacks by examining requests- A traditional network can block the attempts of cross-site scripting (XSS) by employing WAF. If a single IP generates a lot of traffic volume, The WAF can assume that it is an attempt at a Distributed Denial of Service (DDoS) attack.

The following are the major characteristics of API security that differentiate it from the general application security:

A castle with many doors but no moat: Earlier, traditional networks were only required to protect common ports, including 443 (HTTPS) and 80 (HTTP). Modern-day web applications have various APIs that utilize different protocols. APIs generally tend to expand over time, and even a single API can make security a difficult venture.

Incoming request formats which change frequently: APIs evolve very frequently in the DevOps environment, and most of the WAFs cannot accommodate this level's elasticity. Each time an API experiences a change, manual tuning and reconfiguring are required in the traditional security tools. This process is likely to get hit by errors and requires a generous amount of resources and time.

A web browser is typically not used by clients: Most microservice and service APIs are accessed by mobile and native applications or other services and components of the software. Since these clients don't utilize a browser, web security tools are not able to utilize browser verification. As a result, solutions that have their reliability on browser verification in order to detect malevolent bots generally find it difficult to exclude the automatically generated traffic from the endpoints of APIs.

Detection of attacks is not guaranteed just by examining the incoming requests: The requests that look legitimate are exploited by most of the API abuse attacks.

Common API attacks

API attacks are not similar to common cyberattacks and are very difficult to detect. However, this new approach is why every individual should understand the common API attacks, how they function, and the methods to prevent them from happening.

BOLA (Broken Object-Level Authorization) attack

Bola is the most common type of attack that an API faces. This attack is detected when a malicious attacker changes or tries to change parameters across a series of API calls to request sensitive data that only authorized personnel are allowed to access. For instance, malicious users might pass authentication by using one User ID and then enumerate User IDs succeeding API calls to take out account information to which they are not authorized to have access.

Measures to counter the attack: Implement an API tracking that can retain information on the various users connected to the system and all activities they perform. BOLA attacks can be quite "slow and low", drawn out over days or weeks. Hence, you require API tracking, which can store huge amounts of data and implement Artificial Intelligence to detect attack patterns in real-time.

Improper assets management attack

This type of attack happens when there are unmonitored APIs running ("shadow APIs") or older APIs that were created, utilized, and then forgotten about without being replaced or removed with the latest and more secure versions; these APIs are often called zombie APIs.

Unmonitored APIs present a threat as they are not running under the tooling and processes meant to manage APIs. You can never do something that you are not fully aware of. Hence you are required to maintain a complete inventory, even if something was left undocumented by the developers. Older APIs are unmarked, and they often utilize older libraries. These types of APIs are not documented and can go unnoticed for an extended period of time.

Measures to counter the attack: Set up an effective inventory management system that includes every API endpoint, its uses, its versions, and the networks and environment they have its reach.

Ensure that the API is in production, the API being used is not an outdated version, no sensitive data is exposed, and the flow of data is maintained as per the expectations.

Insufficient monitoring and logging

API logs contain personal and private information that the attackers can exploit. Monitoring and logging functions are responsible for providing security teams with the raw data to establish the traditional user behavior patterns. When the API is attacked, the threat could easily be detected by recognizing the usual patterns.

Insufficient monitoring and logging result in user behavior patterns that cannot be traced, allowing the threat actors to compromise the system and go unnoticed for a long time.

Measures to counter the attack: Have a strong and consistent monitoring and logging plan to have sufficient data that could be utilized as a baseline for normal behavior. This way, you can swiftly detect attacks and immediately respond to those incidents in real-time. Also, ensure that whatever data goes into the logs is properly monitored and filtered.

REST API vs SOAP Security

There are, in total, two major architectural styles utilized in modern APIs:

  1. SOAP: A heavily structured message protocol in which multiple low-level protocols are supported.
  2. REST: A less complex approach to APIs utilizing HTTP/S as the protocol for transport and typically utilizing the JSON format for data transfer.

Both the APIs support HTTPS responses and requests and SSL (Secure Socket Layer), but these are the only similarities between these two securities.

SOAP API Security

  • Some extensions are offered by SOAP to the protocol that can address the matters of security.
  • SOAP is based on OASIS and W3C recommendations, which include: XML encryption, XML signatures, and SAML tokens.
  • Web Services (WS) specifications are supported by SOAP, allowing users to utilize security extensions like WS-security that provide enterprise-level security for web services.
  • A built-in error handling is also provided by SOAP as it supports WS-ReliableMessaging.

REST API Security

  • There are no built-in security capabilities provided with REST APIs- the design of the API is the only thing on which the security depends.
  • Security for deployment, interaction, and transmission must be built in.
  • You won't find any built-in error handling in REST APIs and are required to resend data in case of an error.
  • A common choice is to deploy REST APIs after an API gateway. Instead of connecting directly to the REST API, clients connect to the gateway, which behaves like a proxy. This activity allows many security concerns to be addressed by the API gateway.

Overall, SOAP APIs are much more secure by design, but REST APIs can be enhanced when it comes to security; we have to select the right architecture and properly implement it.

Methods of API Security testing

The following are the methods that an individual can follow to manually test their APIs for vulnerabilities security:

Test for parameter tampering

In most scenarios, the parameters that have been sent through API requests can be vulnerable to tempers. For instance, by tempering parameters, attackers can change the purchase amount and even receive products free of cost. Attackers can also manipulate an API to provide sensitive data not meant for the user's account.

Most of the time, parameter tampering is performed by utilizing hidden form fields. You can hunt for the presence of any hidden fields by using the browser element inspector. If you succeed in finding a hidden field, experiment with various values and see how your API is reacting.

Test for command injection

To check whether or not your API has a vulnerability to attacks called command injection, try inserting operating system commands inside the API inputs. Use an appropriate operating system command that perfectly suits the operating system on which your API server is running. Using a harmless operating system command that you can observe on the server is recommended. For example, suppose your API is displaying content with the help of a URL. In that case, an operating system command can be appended by you to the end of the URL in order to observe if the command is getting executed on the server.

Test for API input fuzzing

Fuzzing defines providing an API with random data until you are able to discover a security or functional problem. You can look for signals that the API processed the Inputs incorrectly, returned an error, or crashed.

Test for unhandled HTTP methods

Web applications that use APIs to communicate may utilize various HTTP methods. All these HTTP methods are utilized to store, retrieve, or delete data. You will always get an error message if the server does not support the HTTP method. However, there are exceptions in some cases. If the server side does not support the HTTP method, this creates a vulnerability for security.

Wrapping it up!

Organizations are frequently adopting APIs to help them improve their connectivity. In addition, APIs also help organizations provide easy access to their applications to their clients. But unmonitored and unsecured APIs develop vulnerabilities that could take the form of major security breaches. Hence, it is essential to adopt and implement an effective API security strategy across the overall lifecycle of the APIs.

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