How can you secure a back-end application from attacks?

it is worth mentioning that not only text input should be validated, image uploads or any other systems that interact with media type of files should be scanned before being let into system.

In my journey transitioning from a front-end to a full-stack engineer, I've found input validation to be a cornerstone of back-end security. I've personally experienced how overlooking this simple step can lead to vulnerabilities like SQL injection. In my current stack, which includes Express.js and TypeScript, I often use express-validator for this purpose. It's not just about checking if a field is empty or if an email is in the right format; it's about ensuring that the data entering your system is as clean and secure as possible. This mindset has transformed the way I approach back-end security, making my applications not just functional, but secure in a fortress-like manner.

Securing a back-end application involves key steps. Implement strong authentication, like multi-factor authentication, and use HTTPS for data encryption. Keep software updated, conduct regular security audits, and apply the principle of least privilege for access controls. Validate input to prevent injection attacks, deploy firewalls, and use intrusion detection systems. Regularly back up data and stay informed about emerging threats to ensure a resilient defense.

In my experience, you should never expose your database primary keys, and if you want to pass it to client side, you should encrypt it and never accept anything except what you pass to client-side application. Also, validating inputs in backend, is a primary rule you should always consider and using everything you have, like built-in Attributes in .NET or using Fluent-Validation library and other stuff.

If your back-end application is an API (it most likely is), a good way to do it is to define the validations in the API contract (protobuf, Swagger, etc.). There are frameworks that then handle validation for you and you can keep your application logic simple and focused on the business-level objectives.

In my experience developing backend applications, one thing that is often belittled but is extremely important is ensuring the output contains only what the client needs. The reason being you never want to fully expose the structure of your database tables if you don’t need to. The less attackers know about your system, the better. For this reason some APIs use Graphql because of it’s support for declarative data fetching. Rid your output of unnecessary data!

A great thing to consider is sanitising output in the same place it’s being consumed, browser based DOM sanitisation is much more effective as it’s using the same engine to parse fragments as it does to render it.

Watch out for ORMs here; it is so easy to output the result from an ORM query directly through an API, and before you know it, your user list API that powers your user management SPA is outputting the passwords to the web...

Input sanitization is a critical security measure in web application development. It involves checking, cleaning, and filtering data inputs from various sources, including users, APIs, and web services, to eliminate unwanted characters and strings. By preventing the injection of harmful codes, input sanitization defends against attacks such as SQL injection, cross-site scripting (XSS), and remote file inclusion (RFI). Developers should be meticulous in sanitizing different types of data inputs, such as form submissions, URL parameters, and API responses. Applying proper escape and encoding techniques is essential, depending on the target system, which could be a database or a connected system.

Sanitizing output is like a vigilant gatekeeper, ensuring nothing harmful slips through. It involves meticulously cleaning every piece of data leaving your system to prevent exploits like XSS attacks, utilizing appropriate functions, libraries, or frameworks according to your tech stack, and ensuring that malicious scripts find no entry point. Remember, a well-fortified output is a simple yet effective shield against potential cyber onslaughts.

Use code obfuscation techniques to make reverse engineering harder. Use transport layer encryption (TLS/SSL) for all connections and data transfer. Encrypt data column by column in the database rather than the whole database. Use strong standard encryption algorithms like AES or RSA rather than rolling your own. Hash user passwords with salt before storing them. Avoid storing plain text passwords. Encrypt any sensitive data in transit over networks and at rest in databases. Properly manage keys and passwords. Store them securely, rotate them periodically. When transmitting data, encrypt at the message level, not just the transport channel. Limit access to encrypted data on a need-to-know basis for your staff.

This part is mixing up a lot of different things. Encrypting data is a best practice but it doesn't provide security against attacks. It provides a safety layer to keep the data private. Hashing passwords also is the right thing to do but likely won't protect your app from being attacked. It's to keep password information safe and keep user accounts from being compromised.

Encryption is great to ensure the data is not visible when in the database, or when in transit. However, encryption won’t secure you application but will help secure your data. However, encryption is only good if the key or keys are safe. If they aren’t then it isn’t really encrypted.

The world of encryption is vast and intricate, demanding meticulous attention. Encryption is a powerful tool for safeguarding data however its effectiveness extends beyond keys: correct implementation is vital to ensure true security. So familiarize with cryptographic algorithms and cryptosystems, use key derivation functions (KDFs) and cryptographically secure pseudo-random number generators (CSPRNGs). Choose validated solutions over reinventing the wheel. Use built-in encryption functions and prioritize algorithms that have been approved by reputable entities or standards (NIST, FIPS, etc). Employ strong hashing like SHA-256/512, use HMACs to authenticate messages and implement time-constant verification to counter timing attacks.

Oh absolutely. Having encryption at rest combined with key rotation is like a sweet dream for the security team - tight, secure, and slick. But, let’s be real, it often translates to a bit of a horror story for the production support, DevOps, and engineering crews. Balancing that tightrope between solid security and smooth operability can be a wild ride, for sure.

From my experience, many applications I worked on used OAuth and JWT for authentication purposes. OAuth is a widely-used tool by big tech companies that permits users to link their accounts from other providers and get authenticated. It's crucial for the implementation of authentication to be user-friendly, and OAuth is a convenient solution to help users avoid creating another account. Furthermore, OAuth is an excellent option for reducing development time and cost, as it's easier to implement in web and mobile applications compared to customized security authentication approaches. Therefore, I recommend using OAuth when starting out due to its feasibility to implement and the security making it a great option to consider during dev phase.

I have used OAuth, JWT, custom generated token and PING to authenticate users. OpenID Connect can be used with OAuth2.0 to provide user information and Okta is a good choice as well. Typically, Backend applications validate the token using a filter or interceptor and return 401 or permit the user to access the application.

It's worth mention that JWT and OAuth are separate things. JWT is just a token format, whereas OAuth is an authorization framework. You can use the JWT method to tokenize during the OAuth authorization procedure. It's crucial to know the difference between the two to guarantee strong and safe authentication mechanisms.

Use strong authentication and authorization. Users should be required to authenticate themselves before they can access the application, and they should only be authorized to access the resources that they need. This can be done using a variety of methods, such as passwords, two-factor authentication, and OAuth.

Do not release your own security libraries. Always stick to tried-and-true methods. A lot of these standard libraries have been used before. All security holes are fixed and made better from time to time. Most of these libraries are open source, so if you choose this option, make sure that the repository is being developed actively and bug fixed by the community.

Once a user is authenticated, authorization comes into play, determining what actions or resources they can access based on their role and permissions. For example, in Express js - we create middleware functions to handle authorization. These functions can check whether a user has the necessary permissions to access a specific route or resource. Middleware functions can be applied globally or to particular routes as needed. Storing user authorization is another important point to keep in mind.

Authorization is as important as authentication. It enforces law and order amongst citizens of your application. Except you have a system where the business doesn't restrict action that can be performed, then your team will be saving themselves from avoidable problems.

The fifth crucial step in securing a back-end application is implementing authorization, which involves determining whether users or systems have permission to access specific resources or perform certain actions based on their roles or permissions. This safeguards against unauthorized or inappropriate access. Utilize appropriate built-in functions, libraries, or frameworks for authorization, aligned with your backend language and framework. For instance, in PHP, you can employ $_SESSION to store and verify user roles or permissions. In Express.js, middleware such as express-acl can enforce access control lists (ACLs) based on user roles or permissions, ensuring controlled and secure access.

After you are authenticated, are you authorized to access the resource(s)? If No, backend applications typically returns 403 and prevent the user from modifying or viewing the resource(s). This is very crucial since we can have different categories of users and we need to ensure that the right category of users have authorization to protected modules/features.

- In addition to that, it becomes incredibly crucial to monitor for alerts or unusual behavior when new features are deployed or change requests have been added to ensure everything is working smoothly and not impacting any existing functionality. - This proactive approach to post-deployment monitoring helps in swiftly identifying and addressing any unforeseen issues or conflicts that might arise due to the changes.

Snyk is an amazing tool to find any security vulnerabilities in your application. We should do this test through Snyk regularly to ensure your system is secure. One should also plan penetration testing of the system in a recurring manner to discover any loopholes in it.

There are few steps that can be useful in securing the application. 1) Add Health Checks in you application for all requests, a dashboard reflecting the flow would be more impactful. There are some third parties as well if you could trust them. 2) Add logging and isights to look into the flow of requests 3) Keep yourself updated with latest versions of packages because sometime attacker can enter via those 4) Integrate security focused tools to automatically identify the vulnerabilities

Implement tools for monitoring your API's and take actions under unusual activities. Look for unusual pikes on the requests, multiple login attempts, etc.

In addition to monitoring, I think it’s worth mentioning that keeping logs of your application is also a very crucial step or process for effective monitoring. Through this you can get key insight and information on the performance of your application, security, and vulnerabilities combined with the added advantage of troubleshooting and diagnosing errors.

Here's something actionable and easier to follow: Decrease the surface area of an attack. What this means is to make sure all your APIs are behind singular access points, like API gateways. You then make sure correct policies are applied on the API gateway, making sure you have complete control over accessing the core resources. While this is not a one size fits all solution, it might help someone who hasn't considered this and is prone to an attack.

Rate limiting is also critical to consider. Be it a web server or a back end application processing queued messages, scenarios can occur that cause way too much traffic. These spikes in traffic could be done maliciously as a form of denial of service attack. More often, they happen inadvertently when some other application goes crazy making super high volumes of requests. Building some form of rate limiting can be helpful for multiple reasons.

Securing a back-end application is not just about tech steps; it's also about making sure your team is alert and careful. Think of it like a shared house: everyone should only enter rooms they need to. This is where clear rules help, making sure everyone knows their limits. But, good rules won't work if someone accidentally lets a stranger in. This is why it's important to teach the team about tricks hackers might use, like pretending to be someone they're not to get inside info. By keeping everyone updated about common online threats, you're not just putting up walls but helping each team member be more aware and safe online. In a nutshell: - The principle of least privilege - Cybersecurity Awareness and Trainings - Continuous Monitoring

As a backend system, it's crucial to be mindful of the information that gets recorded in logs. Certain data, such as personally identifiable information (PII), should never be included in logs. Additionally, caution should be exercised to prevent the inadvertent logging of client security credentials, as doing so could potentially result in a security breach through credential exposure.

From the beginning of the project, we should follow all secure steps. Implement strong authentication and authorization Use HTTPS (SSL) Use Secure coding practice WAF (Web Application Firewall) HTTP traffic between a web application and the Internet. It typically protects web applications from attacks such as cross-site forgery, cross-site-scripting (XSS), file inclusion, and SQL injection, among others. Keep versions upgraded. Most secured programming language of 2023 are PHP, Java, Javascript, Ruby, C++, Python, Shell Script