Serverless computing is a rising topic right now in the cloud tech industry. As per a Datadog report, over 50% of organizations in the cloud use some serverless services.

If you are unaware of what serverless means or are hearing it for the first time, this guide is for you. Here we will discuss serverless, their security, the risks & best practices to stay secure.

What does Serverless Mean?

At first, being Serverless doesn’t mean there are no servers behind the technology. In a Serverless, developers do not have to manage the servers behind the scenes.

It is an approach to building and running applications without the need to provision & manage servers or virtual machines.

But, with this convenience comes a security concern. With advancements in software development, security challenges and risks have also increased.

What is Serverless Security?

As serverless is becoming more popular among Software teams, new security threats are also rising.

Serverless security is the protection layer for applications to secure their code functions. From the infrastructure side, organizations don’t need to worry about serverless models. However, there are security concerns that should need to be addressed.

Serverless architectures do not use traditional security methods. It does not have room for firewalls, IDS/IPS tools, instrumentation agents, or server-based protection methods. It is essential to take multiple security steps to secure your serverless apps.

Serverless architectures use small, independent pieces of software; functions. They interact with each other through APIs provided by cloud providers.

Because these APIs are made public when used, they can create a possible security risk. Attackers could access the APIs and compromise the security of the serverless applications.

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What are the most common security challenges & risks with Serverless?

1. Insecure configuration

Cloud service providers offer various options and features with serverless services. But, if the setup & monitoring is not correct, it can create significant security vulnerabilities.

This can provide an opening for attackers to target serverless architectures.

2. Excessive Permissions to Functions

The serverless framework consists of independent functions with specific tasks and responsibilities. These functions often interact with each other in complex ways.

A position can be over-privileged with specific permissions or rights. Many developers take a standard shortcut to use a “wildcard” permission model that covers everything. 

 

This can create vulnerabilities if attacked, and it can infect other functions.

3. Function Event-data injection

Serverless functions can receive input from various event sources. Each event source has its unique message format and encoding methods.

It is crucial to thoroughly examine these event data, as they may contain inputs controlled by attackers.

4. Third-Party Dependencies

Serverless applications involve integrating with external database services, cloud services, and other dependencies.

These third-party integrations can potentially have exploitable vulnerabilities. Developers play a significant role in ensuring security with other application-specific elements.

5. Inadequate Function Monitoring & Logging

While cloud vendors often offer advanced logging capabilities, these logs may not always be sufficient.

Many organizations make the mistake of only relying on default monitoring & logging tools. Inadequate security events tracking at the application level leads to potential risks.

6. Broken Authentication

Serverless applications are stateless. The use of microservices makes the individual functions vulnerable to authentication issues.

For example, improper authentication handling in one function could affect other functions.

Hackers may target a single function to gain access to the system through the dictionary, brute force, or other attacks.

7. Expanded Attack Surfaces

Serverless functions rely on input data from various sources, such as HTTP APIs, cloud storage, IoT devices, and queues.

This broadens the potential for attacks on applications. These sources could contain untested message formats unprotected by standard security measures.

Protocols, vectors, functions & other connections are used to access this input data.  These connections could also be vulnerable to attacks if exposed to weaknesses.

Serverless Security Best Practices. How to secure your serverless functions

In a serverless architecture, you are responsible for securing your application & architecture. You do not need to secure a server like a traditional, server-hosted application.

Instead, it would help if you implemented specific security measures like configuring permissions and access controls.

Remember, detecting intrusions through firewalls is not enough to protect a serverless application.

Instead, it would help if you aimed to prevent intrusions from occurring in the first place. You have to achieve this through a combination of proactive security measures.

These are some best practices to put in place to secure your serverless applications:

1. Use the least privilege principle.

The most overlooked mistake in serverless is – the permissions are set too broad. This leads to larger attack surfaces during attacks on the applications.

To avoid this, it is essential to review each function’s purpose with the DevSecOps team. Each function needs to be assigned specific & necessary permissions only.

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This minimizes individual permissions and creates unique roles for each function. Functions with minimal permissions help maintain a secure system by reducing the attack surface.

2. Secure third Party dependencies

Ensuring the reliability and security of third-party platforms and links used is crucial. 

This can help prevent vulnerabilities and keep your app safe. To avoid potential vulnerabilities, it is also essential to use the latest versions of open-source components.

Check development forums, use automated dependency scanner tools, & avoid too many third-party dependencies. By taking these precautions, you can ensure that your app is secure and up to date.

3. Code Audit

Black Duck Software surveyed 1000 commonly used enterprise applications. The report shows 96% of the surveyed applications used open-source software. 60% contained security vulnerabilities, some more than four years old.

This poses a significant security risk as the authenticity and ownership of the code cannot be trusted.

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This type of attack is known as “Poisoning the Well,” It involves attackers inserting malicious code into popular projects and waiting to infiltrate.

To enhance AWS security, performing a code security audit is crucial. Applications with various libraries and modules are mainly vulnerable to this attack.

A single serverless function may include thousands of lines of code from various external sources.

4. Sufficient Serverless Monitoring and Logging

As functions are regularly deployed, the number of function invocations increases with scaling.

It can be challenging to keep track of the flow of events and identify the source of errors due to their brief lifespan.

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It is recommended to evaluate all functions frequently. This enhances visibility into functions by tracing them end-to-end & detecting problems quicker.

Additionally, it is essential for security teams to review audits and network logs consistently.

Metrics to observe: 

• • Monitoring the number of failed executions.

• • Counting the number of functions that have been run.

• • Evaluating the performance of functions by measuring the time it takes for them to execute.

• • Determining the concurrency level based on the frequency of function execution.

• • Monitoring the use of provisioned concurrency.

• • Consolidating logs from multiple accounts for immediate analysis.

5. Isolated Function Perimeters

Each function should be treated as a separate perimeter. This way, if one function gets compromised, it will not be able to compromise the other functions. To ensure that functions are isolated within their perimeter, you should:

• • Avoid relying on the order in which functions are accessed or invoked. This can change over time and should not be relied upon.

• • Treat each function as its security perimeter. Every function should handle untrusted inputs and take steps to sanitize the input before processing it.

Implement standardized security libraries. This will ensure the security of functions and that they all use the same security measures. Make sure to mandate their use across all functions.

6. Handling Credentials

Store sensitive credentials like databases in secure locations and limit access to them. Pay extra attention to critical credentials like API keys.

Set environment variables to run time-evaluation settings and then deploy time in configuration files.

If the same configuration file is used in multiple functions, you have to redeploy services if variables are set at deployment time.

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The best method is to rotate the keys regularly, even if you’re hacked, as it ensures that access to hackers is cut off.

Every component, developer, and the project should have separate keys. Sensitive data and environment variables should be encrypted using encryption helpers.

7. Separate Application Development Environments

Separate the application development environments, such as staging, development, and production.

By doing so, it is possible to implement CI/CD best practices. This approach helps prioritize vulnerability management at every stage of development.

It allows for continuous testing and improvement of the application through patch prioritization, update protection, and vulnerability identification.

This helps developers in ensuring the security of the application from potential attackers.

8. Protect with more than WAF

• • WAF will only protect functions triggered by the API Gateway and only inspect HTTP(s) traffic. It will not protect functions triggered by other event sources or event trigger types.

Serverless architecture presents a new approach to creating applications. It offers advantages in cost-effectiveness, scalability, and ease of infrastructure management.

Yet, it comes with its own set of challenges. This architecture shifts the focus from managing infrastructure to developing high-quality code.

It is essential to be mindful of serverless security concerns and challenges. Follow security best practices when entrusting cloud providers with your application infrastructure.

Serverless is being adopted more and more. With this growing popularity, cloud providers are adding needed serverless security features.

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Despite newer security features, it’s up to the developers to adopt best practices & prevent any loopholes for security. 

Implement the best security measures & build and deploy secure serverless applications confidently.

Serverless Security Tools

PureSec

PureSec is one of the most popular end-to-end security provider for AWS Lambda, Azure functions, Google Cloud Functions and many more. Additionally, it integrates with other popular tools and platforms such as, Gitlab, Jenkins, Apex, AWS Cloudformation, Serverless framework and many others.

Moreover, It detects and prevents the attacks at function event-data layer without impacting the performance on serverless application firewall.

Frequently Asked Questions in Serverless Security