WAF-web application firewall appliance
A web application firewall is a special type of application firewall that applies specifically to web applications. It is deployed in front of web applications and analyzes bi-directional web-based (HTTP) traffic - detecting and blocking anything malicious. The OWASP provides a broad technical definition for a WAF as “a security solution on the web application level which - from a technical point of view - does not depend on the application itself.” According to the PCI DSS Information Supplement for requirement 6.6, a WAF is defined as “a security policy enforcement point positioned between a web application and the client endpoint. This functionality can be implemented in hardware, running in an appliance device, or in a typical server running a common operating system. It may be a stand-alone device or integrated into other network components.” In other words, a WAF can be a physical appliance that prevents vulnerabilities in web applications from being exploited by outside threats. These vulnerabilities may be because the application itself is a legacy type or it was insufficiently coded by design. The WAF addresses these code shortcomings by special configurations of rule sets, also known as policies.
Previously unknown vulnerabilities can be discovered through penetration testing or via a vulnerability scanner. A web application vulnerability scanner, also known as a web application security scanner, is defined in the SAMATE NIST 500-269 as “an automated program that examines web applications for potential security vulnerabilities. In addition to searching for web application-specific vulnerabilities, the tools also look for software coding errors.” Resolving vulnerabilities is commonly referred to as remediation. Corrections to the code can be made in the application but typically a more prompt response is necessary. In these situations, the application of a custom policy for a unique web application vulnerability to provide a temporary but immediate fix (known as a virtual patch) may be necessary.
WAFs are not an ultimate security solution, rather they are meant to be used in conjunction with other network perimeter security solutions such as network firewalls and intrusion prevention systems to provide a holistic defense strategy.
WAFs typically follow a positive security model, a negative security model, or a combination of both as mentioned by the SANS Institute. WAFs use a combination of rule-based logic, parsing, and signatures to detect and prevent attacks such as cross-site scripting and SQL injection. The OWASP produces a list of the top ten web application security flaws. All commercial WAF offerings cover these ten flaws at a minimum. There are non-commercial options as well. As mentioned earlier, the well-known open source WAF engine called ModSecurity is one of these options. A WAF engine alone is insufficient to provide adequate protection, therefore OWASP along with Trustwave's Spiderlabs help organize and maintain a Core-Rule Set via GitHub to use with the ModSecurity WAF engine.
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F.A.Q. about WAF-web application firewall appliance
A Web Application Firewall or WAF provides security for online services from malicious Internet traffic. WAFs detect and filter out threats such as the OWASP Top 10, which could degrade, compromise or bring down online applications.
What are Web Application Firewalls?
Web application firewalls assist load balancing by examining HTTP traffic before it reaches the application server. They also protect against web application vulnerability and unauthorized transfer of data from the web server at a time when security breaches are on the rise. According to the Verizon Data Breach Investigations Report, web application attacks were the most prevalent breaches in 2017 and 2018.
The PCI Security Standards Council defines a web application firewall as “a security policy enforcement point positioned between a web application and the client endpoint. This functionality can be implemented in software or hardware, running in an appliance device, or in a typical server running a common operating system. It may be a stand-alone device or integrated into other network components.”
How does a Web Application Firewall wWork?
A web application firewall (WAF) intercepts and inspects all HTTP requests using a security model based on a set of customized policies to weed out bogus traffic. WAFs block bad traffic outright or can challenge a visitor with a CAPTCHA test that humans can pass but a malicious bot or computer program cannot.
WAFs follow rules or policies customized to specific vulnerabilities. As a result, this is how WAFs prevent DDoS attacks. Creating the rules on a traditional WAF can be complex and require expert administration. The Open Web Application Security Project maintains a list of the OWASP top web application security flaws for WAF policies to address.
WAFs come in the form of hardware appliances, server-side software, or filter traffic as-a-service. WAFs can be considered as reverse proxies i.e. the opposite of a proxy server. Proxy servers protect devices from malicious applications, while WAFs protect web applications from malicious endpoints.
What Are Some Web Application Firewall Benefits?
A web application firewall (WAF) prevents attacks that try to take advantage of the vulnerabilities in web-based applications. The vulnerabilities are common in legacy applications or applications with poor coding or designs. WAFs handle the code deficiencies with custom rules or policies.
Intelligent WAFs provide real-time insights into application traffic, performance, security and threat landscape. This visibility gives administrators the flexibility to respond to the most sophisticated attacks on protected applications.
When the Open Web Application Security Project identifies the OWASP top vulnerabilities, WAFs allow administrators to create custom security rules to combat the list of potential attack methods. An intelligent WAF analyzes the security rules matching a particular transaction and provides a real-time view as attack patterns evolve. Based on this intelligence, the WAF can reduce false positives.
What Is the Difference Between a Firewall and a Web Application Firewall?
A traditional firewall protects the flow of information between servers while a web application firewall is able to filter traffic for a specific web application. Network firewalls and web application firewalls are complementary and can work together.
Traditional security methods include network firewalls, intrusion detection systems (IDS) and intrusion prevention systems (IPS). They are effective at blocking bad L3-L4 traffic at the perimeter on the lower end (L3-L4) of the Open Systems Interconnection (OSI) model. Traditional firewalls cannot detect attacks in web applications because they do not understand Hypertext Transfer Protocol (HTTP) which occurs at layer 7 of the OSI model. They also only allow the port that sends and receives requested web pages from an HTTP server to be open or closed. This is why web application firewalls are effective for preventing attacks like SQL injections, session hijacking and Cross-Site Scripting (XSS).
When Should You Use a Web Application Firewall?
Any business that uses a website to generate revenue should use a web application firewall to protect business data and services. Organizations that use online vendors should especially deploy web application firewalls because the security of outside groups cannot be controlled or trusted.
How Do You Use a Web Application Firewall?
A web application firewall requires correct positioning, configuration, administration and monitoring. Web application firewall installation must include the following four steps: secure, monitor, test and improve. This should be a continuous process to ensure application specific protection.
The configuration of the firewall should be determined by the business rules and guardrails by the company’s security policy. This approach will allow the rules and filters in the web application firewall to define themselves.