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API Security 101: API Security Strategy and Fundamentals Guide

APIs are at the core of today’s digital innovation initiatives and have become the number one attack vector for applications. Find out what API security is, why it is so important, and what you can do to protect your APIs against modern threats.

What is API Security?

Application programming interfaces (APIs) are the building blocks of modern applications. Think of them as the on-ramps to the digital world. They keep everyone connected to vital data and services, enable all sorts of critical business operations, and make digital transformation possible.

As the number of APIs continues to grow and with organizations around the world relying on them more and more to deliver their critical business initiatives, they have become a prime target for attackers. Our State of API Security Report Q1 2023 shows that unique attackers have grown by 400% within a six-month period. And yet, 30% of respondents still have no API security strategy in place.

The Open Web Application Security Project (OWASP) defines API security as focusing on strategies and solutions to understand and mitigate the unique vulnerabilities and security risks of APIs — of which there are many.

Read on to learn why API security has become a critical concern for today’s organizations and how it’s different to application security.

Learn why APIs present unique risks and best practices for securing them

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Why is API Security important?

APIs have become a primary attack vector for cybercriminals, with bad actors realizing how lucrative it is to target the APIs that connect today’s digital services and sensitive data. In fact, according to the State of API Security Report Q1 2023, 94% of companies experienced API security problems in production APIs within the past year. In 2017, analyst firm Gartner predicted that by 2022 APIs would become the primary attack vector for cybercriminals and they have certainly been proven right. With API attacks making headlines around the world in recent years, Gartner has included API security in its security reference architecture in 2022, recognizing the need for dedicated API security tools and methods.


By 2022, API abuses will move from an infrequent to the most-frequent attack vector, resulting in data breaches for enterprise web applications.”

20 November 2017
“Predicts 2018: Infrastructure Protection”
—Strategic Planning Assumption

…and now

As 2022 approaches, this prediction could arguably be counted as ‘missed’ — but only because we underestimated the steep rise in attacks on APIs.”

6 December 2021
“Predicts 2022: APIs Demand Improved Security and Management”


The critical importance of API security is also becoming increasingly obvious for senior officials in today’s organizations. In fact, almost half (48%) of our State of API Security survey respondents indicated that API security has now become a C-level discussion. This finding is also supported by the results of a global survey conducted by independent research company Global Surveyz on behalf of Salt Security, where the majority (78%) of CISOs globally said that API security is a higher priority today than it was two years ago, and 95% said that API security will a top priority over the next two years.

Although traditional security measures, such as API gateways and Web Application Firewalls (WAFs) can add value to an organization’s security stack, they cannot keep up with today’s increasingly sophisticated API attack methods. In fact, they’re not keeping attackers from stealing sensitive data, affecting the user experience, or causing other damage. To prevent and mitigate API attacks, you need a security strategy and technology that is purpose-built for APIs.

Attacks have changed and they’re easy to miss

Bad actors targeting APIs have moved beyond traditional “one-and-done” attacks such as SQLi and XSS. Their focus now is on finding vulnerabilities in the business logic of APIs. Your APIs are unique, so the attacks have to be as well. It takes attackers days, weeks, or even months to probe and learn your APIs, and they use “low-and-slow” techniques that stay under the radar of traditional security tools.


One and done
Single API call – seconds to minutes

Known attacks – SQLi, XSS, etc.


Low and slow
Sequence of API calls – days to weeks
Business logic attacks – requires context

The Different Types of API Security: From REST APIs to SOAP and GraphQL

REST API security, SOAP security, and GraphQL security all play an important role in ensuring the protection of APIs and web applications. Each of these technologies has a different approach to security which requires specific security considerations.

REST API Security

REST stands for Representational State Transfer and is an architectural style commonly used in web services. It relies on standard HTTP methods such as GET, POST, PUT, DELETE and uses URLs to identify resources.  REST APIs bring their unique set of security considerations, such as:

  • Authentication mechanisms — REST APIs often use authentication mechanisms such as API keys, OAuth tokens, or JSON Web Tokens (JWT) to verify the identity of clients and grant access to resources.
  • Authorization mechanisms: After a user is authenticated, REST APIs use authorization mechanisms to control what resources they can access.
  • Rate limiting: Implement rate limiting to restrict the number of requests a client can make within a certain timeframe, preventing abuse and DoS attacks.
  • Input validation: This must be applied to prevent common security vulnerabilities like SQL injection and Cross-Site Scripting (XSS) attacks.
  • HTTPS encryption: Encrypting the data transmitted between the client and the server is essential in REST APIs. HTTPS encryption is used to prevent unauthorized interception.
  • Cross-origin resource sharing (CORS): CORS headers must be used in REST architecture to control which domains can access the API at hand.

To protect REST APIs effectively, all these aspects must be taken into account, in addition to other REST API security best practices.

SOAP Security

SOAP (Simple Object Access Protocol) is a protocol used to exchange information in web services. It generally uses XML and relies on other web protocols such as HTTP, SMTP and TCP. There are also some important security considerations for SOAP:

  • Sensitive data encryption: Sensitive data in SOAP messages should be encrypted to ensure confidentiality during transit.
  • XML validation: validating XML against a predefined schema helps prevent XML injection and related attacks.
  • WS-security standard: SOAP offers this security standard for securing messages, which includes features like message integrity, confidentiality, authentication, and authorization.
  • HTTPS security: Similarly to REST APIs, SOAP messages should be transmitted over HTTPS encryption to secure the data being transmitted.
  • Digital signatures: Digital signatures should be used whenever possible to assess the integrity and legitimacy of SOAP messages.

GraphQL Security

GraphQL is a query language for APIs and a runtime for executing those queries with a backend system. Unlike REST, which exposes multiple API endpoints for different resources, GraphQL uses a single endpoint for all queries. Here are some of the most important security considerations for GraphQL:

  • Authentication and authorization: GraphQL APIs must implement authentication and authorization mechanisms to control access to various queries and mutations. In recent years, bad actors have been known to exploit GraphQL authorization vulnerabilities successfully to execute API attacks.
  • Rate limiting: Applying rate limiting is essential to control the number of GraphQL queries a client can execute at a given time.
  • Input validation: Validating and sanitizing user inputs in GraphQL can help prevent common security vulnerabilities.
  • Query depth limits: Setting limits to the depth of GraphQL queries must be done to prevent complex and resource-intensive queries that could lead to denial-of-service (DoS) attacks.

Ultimately, the security of any API, whether REST, SOAP, or GraphQL, depends on a combination of best practices that cover authentication and authorization mechanisms, data validation, and the use of secure communication protocols. A robust API security strategy that covers discovery, runtime protection and shift-left practices is essential to keep APIs protected against emerging threats.

Salt – complete API security for complete protection

Salt Security API protection covers the full API lifecycle, including Discovery, Threat Protection, and Remediation.

What Are the Most Common Types of API Attacks?

The first step to being able to effectively protect APIs is understanding why today’s attacks are different. Today’s most common API attacks can be split into four categories:

Lack of visibility and governance

In this type of attack, the attackers take advantage of APIs that are either completely unknown to an organization — shadow or zombie APIs — or APIs whose security posture is not visible, such as unmanaged or third-party APIs.

Abuse and misuse of APIs

To execute this type of attack, a bad actor will use an API exactly as designed but leverage the results in an unintended and malicious manner by exploiting design or development flaws that allow for malicious outcomes, such as data exfiltration.

Business logic flaw exploitation

In a business logic-based attack, hackers will use reconnaissance techniques over time to poke for vulnerabilities in each API’s unique business logic. During the reconnaissance phase, which can last days, weeks or even months, attackers seek areas to explore, such as gaining unauthorized access to data or functionality within the API.

Stolen credentials and social engineering

This type of threat manifests when a bad actor uses social engineering techniques to access privileged API keys. This allows them to steal credentials and use the API as if they were a legitimate, authenticated user or admin. According to the State of API Security Report Q1 2023, in the last year, 78% of attacks came from seemingly legitimate users who have maliciously achieved the proper authentication.

OWASP API Security Top 10

To help the API security industry gain a deeper understanding of the most common API attacks, the Open Web Application Security Project (OWASP) released its first-ever API Security Top 10 list of vulnerabilities in 2019. The list has been updated in 2023 and lists the ten more significant API vulnerabilities. Of these, the most common are:

API1:2023 Broken Object Level Authorization

Broken object level authorization (BOLA) represents around 40% of API attacks and is the most common API threat.

As APIs frequently expose endpoints that handle object IDs, this creates a large potential attack surface. Object level authorization is an access control method that is typically implemented at the code level to verify a user's ability to access a certain object. Modern applications use a variety of intricate and pervasive authorization and access control systems. Developers frequently neglect to apply these checks before accessing an object, even when an application includes a robust infrastructure for authorization checks. Attackers can easily exploit API endpoints that are vulnerable to broken object level authorization by manipulating the ID of an object that is sent within an API request. BOLA authorization flaws can lead to data exfiltration as well as unauthorized viewing, modification, or destruction of data. Ultimately, BOLA can lead to full account takeover (ATO).

API2:2023 Broken User Authentication

Attackers can easily target authentication processes, especially if they are fully exposed or accessible to the public. The second most frequent vulnerability reported by OWASP is broken user authentication, which enables attackers to utilize credential stuffing, stolen authentication tokens, and brute-force attacks to obtain unauthorized access to apps. Attackers are then able to control users' accounts, gain unlawful access to other users' data, and conduct unauthorized transactions. Technological issues, such as inadequate password complexity, missing account lockout criteria, overly long rotation times for passwords and certificates, or the usage of API keys as the only authentication method, can result in faulty authentication in APIs.

Attackers who can successfully take advantage of weaknesses in authentication procedures may be able to access another user's data without authorization and carry out illicit transactions using that user's account.

API3:2023 Broken Object Property Level Authorization

Broken Object Property Level Authorization merges attacks that happen by gaining unauthorized access to sensitive information by way of Excessive Data Exposure (previously listed as number 3 in the 2019 OWASP API Security Top 10) or Mass Assignment (previously in sixth place in the 2019 list). Both techniques are based on API endpoint manipulation to gain access to sensitive data.

The main reason for introducing this new threat on the list is that, even if an API can enforce sufficient object-level authorization security measures, this might still not be enough to protect it. More specific authorization that covers the objects and their characteristics is often required. The varying access levels within an API object must also be considered, as an API object often has both a public property and a private one.

API4:2023 Unrestricted Resource Consumption

The Unrestricted Resource Consumption vulnerability has replaced the previous number 4 in the OWASP API Security Top 10, Lack of Resources and Rate Limiting. However, while the name changed, this vulnerability remains the same overall.

Resources, like the network, CPU, memory, and storage, are used up by API calls. The user's input and the endpoint's business logic have a significant impact on the number of resources needed to fulfill a request. The size or quantity of resources that a client or user may request may not necessarily be constrained by APIs. This not only has the potential to negatively affect API server performance and cause Denial of Service (DoS), but it also makes APIs that support authentication and data retrieval vulnerable to brute-force and enumeration assaults, including token and credential cracking.

According to the State of API Security Report Q1 2023, only 54% of respondents prioritize the OWASP API Security Top 10 as part of their security programs, even though 62% of attempted attacks against organizations leverage at least one of those methods.

OWASP API Security Top 10 Threats.

What Makes API Security Different?

Traditional security solutions including WAFs, API gateways, API management tools, and identity and access management (IAM) tools weren’t designed to prevent attacks on APIs. That’s because securing APIs offers unique challenges:

API Sprawl: A Constantly Changing Landscape

With APIs constantly being developed and changed by today’s DevOps teams, the types of threats faced by APIs have also changed. In the past, transaction-based attacks, such as SQL injection and other code execution methods, were the most prevalent tactics, but today’s attacks often aim to exploit the underlying application and business logic behind each API. With 37% of companies updating their APIs once a week, it’s not realistic to expect development teams to spot every possible API vulnerability before deploying a new or updated API.

Low-and-Slow API Attacks: The Power of Reconnaissance

Traditional attacks, like SQL injections or cross-site scripting, still happen, but today’s most successful, application logic-based API attacks don’t follow those kinds of “one-and-done” mechanisms that leverage known vulnerabilities. Because every API endpoint is different and each attack rarely stems from a single API call, every API attack is essentially a zero-day attack, with traditional tools being unable to detect them via their rule-based and signature approaches. Bad actors are taking their time with their reconnaissance activities. They may take weeks or even months to look for data, poking for flaws and inducing abnormal behavior to find subtle ways to disrupt the supply chain or exfiltrate data from an API.

The Shortcomings of Shift-Left Tactics and the Need for Runtime Protection

Historically, organizations have relied on testing to spot security flaws before deploying an application. However, the widespread adoption of agile development methodologies and the issue of API sprawl have made testing for every single API vulnerability simply impossible. While standard pre-production testing can find some gaps in API security best practices, they won’t uncover vulnerabilities rooted in API business logic gaps — which are precisely the flaws that today’s attackers will aim to exploit. Additionally, it is not realistic to expect any developer to write fully secure code every time, so the only way to detect and stop API threats is to have runtime protection in place.

Understanding API Attacks: Why are they different and how can you stop them?

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What API Security Best Practices Can Be Used to Prevent and Mitigate Today’s Attacks?

APIs are challenging to protect. Traditional solutions can’t handle the complexities of the API ecosystem. Attackers know this, which is why they focus on APIs.

The following best practices can help you improve your API security posture:

Development and Testing

  • Promote secure API design and development: Create secure coding and configuration practices for building and integrating APIs. The OWASP Application Security Verification Standard (ASVS) is a good resource.
  • Reduce exposure of sensitive data: Avoid sending too much data to client apps and then relying on them to filter the data.
  • Conduct design reviews: Be sure to include business logic in design reviews.
  • Document your APIs: Documentation helps people understand how an API is built or integrated. You especially need documentation for design reviews, security testing, and protection.
  • Use a machine format for documentation: Use machine formats such as OpenAPI Specification (OAS). Then you can use the specs for basic testing and protection.
  • Maintain an accurate API inventory: Give your security teams a realistic view of the attack surface with an up-to-date inventory. The best way to capture this information is with automated API discovery that covers REST, GraphQL, and other API formats.
  • Do security testing: Use security testing tools to identify configuration issues or vulnerabilities in your APIs. Scanners aren’t good at parsing business logic, so you should analyze your APIs and conduct fuzz testing in runtime to identify exploitable code.


  • Turn on logging and monitoring: Telemetry data helps you detect attacks, respond to incidents, and protect APIs in runtime. Use the data as your baseline for normal behavior. That way any outlier events can be quickly identified and resolved.
  • Mediate your APIs: Use mediation tools like API gateways to improve visibility and security. Extend the capabilities of these platforms with an API security solution that provides deeper context about APIs.
  • Identify API drift: Make sure you have a plan for figuring out when an API has changed. Again, automated platforms that can compare documentation against the runtime behavior of your APIs will help identify these gaps. Then update your documentation accordingly.
  • Use the right network security controls: Some network controls can help with API security. For example, encrypt the data APIs are sending. You can also use dynamic rate limiting and IP address allow and deny lists (assuming the number of API users is small).
  • Continuously authenticate and authorize: Make access controls and identity stores external. Include API gateways, identity stores, IAM, key management, public key infrastructure, and secrets management in this step. Avoid using API keys for authentication.
  • Deploy runtime protection: Make sure your runtime protection can identify configuration issues in API infrastructure. It should also detect behavior anomalies such as credential stuffing, brute forcing, or scraping attempts.

What Methods and Tools Can Be Used to Protect APIs?

The best protection for APIs is a dedicated platform built from the ground up with API security in mind. The right API security platform should automatically:

  • Discover all new and changed APIs, as well as any sensitive data they expose.
  • Detect and stop attacks on APIs during the reconnaissance phase.
  • Eliminate vulnerabilities in the build phase whenever possible, by providing actionable insights to your development teams.

Protection across the entire API lifecycle

API Security across the entire API lifecycle.

A complete API security solution should be able to collect, store, and analyze hundreds of attributes across millions of users and API calls and, more importantly, leverage artificial intelligence (AI) and machine learning (ML) to correlate them over time. Gaining this breadth of context will require cloud-scale big data, as server or virtual machine-based approaches won’t have a broad enough data set over time to identify today’s sophisticated, low and slow API attacks. Only with this kind of adaptive intelligence and deep context will you have what you need to protect all your APIs.

To learn more about how Salt can help defend your organization from API risks, you can connect with a rep or schedule a personalized demo.

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