Introduction to Web Application Firewall (WAF)

Data packets traveling to and from a website or web application are watched, filtered, and blocked by a firewall known as a web application firewall (WAF). A WAF is frequently installed via a reverse proxy and positioned in front of one or more websites or apps. It might be network-based, host-based, or cloud-based. 

 

The WAF inspects each packet and employs a rule base to evaluate Layer 7 web application logic and filter out potentially dangerous traffic that might aid web attacks. It can run as a network appliance, server plugin, or cloud service.

 

Enterprises frequently utilize web application firewalls as a security measure to guard against malware infections, impersonation attacks, zero-day exploits, and other known and unknowable threats and vulnerabilities. While standard network firewalls, other intrusion detection systems (IDSes), and intrusion prevention systems (IPS) might not be able to achieve so, a WAF can use tailored inspections to quickly identify and stop some of the most hazardous web application security issues. 

 

WAFs are particularly beneficial to businesses that offer services or goods online, such as e-commerce, online banking, and other interactions with clients or partners.

 

Working of WAF:

 

A WAF examines Hypertext Transfer Protocol (HTTP) requests and applies a set of rules that identify the malicious and benign components of each exchange. A WAF primarily examines the GET and POST requests in HTTP interactions. To modify the state of a server, data must be sent with POST requests as opposed to GET requests, which are used to get data from the server.

 

In addition to filtering, monitoring, and blocking any malicious HTTP/S traffic that tries to access the web application, a WAF also stops unauthorized data from exiting the app, protecting your web apps from outside threats. By abiding by a set of policies that assist in distinguishing between safe and malicious communication, it does this. Similar to how a proxy server functions as a middleman to shield a client's identity, a WAF—also known as a reverse proxy—operates similarly to shield the web app server from potentially harmful clients.

 

Software, appliances, or as-a-service offerings are all possible forms of WAFs. If your online application or group of web apps has particular requirements, policies can be tailored to fit those needs.

 

When evaluating and filtering the content of these HTTP requests, a WAF can use one of two methods, or a blend of the two:

 

1. Whitelisting: 

 

With a whitelisting strategy, the WAF will by default reject all requests and only permit those that are known to be trustworthy. It offers a list of IP addresses that have a reputation for being secure. Blacklisting uses more resources than whitelisting does. A whitelisting strategy has the drawback of potentially blocking good traffic by accident. It can be effective and throws a large net, but it also has the potential to be inaccurate.

 

2. Blacklisting: 

 

A blacklisting strategy employs predefined signatures to prohibit harmful online traffic and guard against vulnerabilities in websites or web apps by default allowing packets to pass. It is a collection of guidelines for identifying malicious packets. Since public websites and online apps get a lot of traffic from unknown IP addresses that aren't recognized to be malicious or benign, blacklisting is more suitable for them. 

 

The drawback of a blacklisting strategy is that it consumes more resources; in contrast to using trusted IP addresses by default, filtering packets based on specific criteria requires more information.

 

3. Hybrid security:

 

The security that combines parts of blacklisting and whitelisting is known as a hybrid security. What matters most is that a WAF analyzes HTTP interactions and reduces or, preferably, eliminates harmful traffic before it reaches a server for processing, regardless of the security architecture it employs.

 

Importance of WAF:

 

Since it helps stop data leakage, a WAF is crucial for the expanding number of businesses that offer products online, such as online banks, social media platform providers, and mobile application makers. Many critical pieces of information, like credit card information and client details, are kept in back-end databases that may be accessed by online apps. These programs are routinely targeted by attackers who want access to the underlying data.

 

To comply with the Payment Card Industry Data Security Standard (PCI DSS), which is a collection of guidelines to guarantee that cardholder data (CHD) is safeguarded, banks, for instance, may deploy a WAF. One of the 12 criteria for PCI DSS compliance is the installation of a firewall. Any company that deals with CHD must comply with this regulation.

 

A rising amount of transactions take place at the application layer utilizing the web since many younger enterprises use mobile applications and the expanding internet of things (IoT). A WAF is a crucial component of a contemporary company's security posture because of this.

 

A WAF is crucial, but it works best when combined with additional security tools like IPSes, IDSes, and conventional or next-generation firewalls (NGFWs). A WAF should ideally be positioned alongside other firewall types, like NGFWs, and security elements, such IPSes, and IDSes, which are frequently incorporated in NGFWs, in a holistic business security model.

 

Since it provides more insight into sensitive application data that is transmitted across the HTTP application layer, a WAF has an advantage over conventional firewalls. It can stop application layer assaults like the ones listed below, which typically get past conventional network firewalls:

 

• Attackers can insert and run malicious scripts in another user's browser thanks to cross-site scripting (XSS) vulnerabilities.

• Any program that uses a SQL database is susceptible to SQL injection attacks, which give hackers access to and the capacity to alter sensitive data.

• Attackers can assume the identity of a legitimate user by stealing a session ID thanks to web session hacking. Typically, a cookie or Uniform Resource Locator contains a session ID (URL).

• DDoS attacks overwhelm a network by saturating it with traffic to the point where it is unable to provide services to its users. Network firewalls and WAFs can both stop this kind of attack, but they do so from different angles.

 

A WAF also has the benefit of being able to defend web-based applications without necessarily having access to their source code. A cloud-hosted WAF can defend the application without having access, in contrast to a host-based WAF that can be integrated into the application code. 

 

A cloud WAF also offers quick virtual patching solutions that let users quickly modify their settings to adapt to newly discovered threats, and it is simple to deploy and manage.

 

Differences between WAF and firewall:

 

Firmware that protects a computer network by filtering incoming data packets is referred to as a "firewall" in general. Other categories fall under that broad term, and they may be distinguished by the types of protection they offer and the methods by which they do so. Packet filtering, stateful inspection, proxy, and NGFW are a few of these labels.

 

Another type of firewall is a WAF, which differs from other firewalls by the degree to which it filters data packets. When compared to other types, such as packet filtering and stateful inspection, the WAF is special since it only concentrates on web-based attackers at the application layer. The most similar security measure to a proxy firewall is a WAF, however, it specializes in Layer 7 application logic.

 

Types of WAF:

 

The different types of web application firewalls are discussed below:

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Types of WAF

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1. Network-based WAFs:

 

Network-based WAFs are often hardware-based and can lower latency since they are placed as near to the application as feasible locally on-premises through a dedicated appliance. Large-scale deployment, setup, and management are made possible by the majority of the leading network-based WAF vendors' support for rules and setting replication over several appliances. Cost is the key disadvantage of this kind of WAF product; there is an initial capital investment as well as continuing operating expenditures for upkeep.

 

2. Host-based WAFs:

 

Host-based WAFs may be completely incorporated into the actual application code. Lower costs and more customization options are two advantages of a host-based WAF implementation. Due to their dependency on local server resources and the need for application libraries, host-based WAFs can be difficult to manage. DevOps/DevSecOps, system analysts, and other staff members may be needed in greater numbers as a result.

 

3. Cloud-hosted WAFs:

 

For businesses looking for a turnkey product that requires little in the way of resources for setup and monitoring, cloud-hosted WAFs provide an affordable option. Cloud WAFs are straightforward to set up, offered on a subscription basis, and frequently simply need a minor update to the domain name system (DNS) or proxy to reroute application traffic. 

 

The strategy enables applications to be protected across a broad spectrum of hosting locations and uses similar policies to protect against application layer attacks, even though it can be difficult to assign responsibility for filtering an organization's web application traffic to a third-party provider. 

 

Additionally, these third parties have access to the most recent threat intelligence and may assist in identifying and thwarting the most recent threats to application security.

 

Features of WAF:

 

Typically, web application firewalls provide the following functions and features:

 

1. Attack signature databases:

 

Attack signatures are patterns in traffic, such as request types, strange server responses, and known malicious IP addresses, that may point to malicious activity. Earlier WAFs relied heavily on attack pattern databases, which were less efficient against fresh or undiscovered threats.

 

2. AI-powered traffic pattern analysis:

 

This entails looking into an application's structure, including the common queries, URLs, values, and allowed data types. This makes it possible for the WAF to recognize and deny potentially malicious requests.

 

3. Application profiling:

 

The security guidelines that apply to application traffic can be set by operators. As a result, enterprises can tailor WAF behavior to their requirements and stop the blockage of genuine traffic.

 

4. Correlation engines:

 

These examine incoming traffic and classify it using custom rules, application profiling, AI analysis, and known threat signatures to determine whether it needs to be blocked.

 

5. DDoS protection platforms:

 

A cloud-based infrastructure that defends against distributed denial of service (DDoS) assaults can be integrated. The DDoS defense platform, which can manage a large volume of attacks, can receive traffic if the WAF detects a DDoS attack.

 

6. Content delivery networks (CDNs):

 

A cloud-hosted WAF can offer Content delivery networks (CDNs) to cache the website and reduce load times since WAFs are implemented at the network edge. Users are served from the closest PoP thanks to the WAF's deployment of the CDN over several internationally dispersed points of presence (PoPs).

 

Conclusion:

 

A growing number of businesses, such as social media service providers, digital banks, and developers of mobile applications, are realizing the value of WAFs. A WAF can assist you in securing sensitive information and preventing leakages, such as customer records and payment card information.

 

Most sensitive information is typically kept by businesses in a backend database that can be accessed through web applications. Businesses are using mobile apps and IoT devices more frequently to streamline business interactions, with many online transactions taking place at the application layer. For access to this data, attackers frequently target programs.