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Web Application Firewall:What is WAF?

Last Updated:Apr 06, 2023

Web Application Firewall (WAF) provides end-to-end security protection for your websites or apps. WAF identifies, scrubs, and filters out malicious web traffic, and then forwards normal traffic to your origin servers. This protects your origin servers against attacks and ensures data and service security.




Service specifications

WAF protects websites by monitoring and filtering HTTP and HTTPS traffic.

Web application protection

Protection against common web application attacks

  • WAF protects websites against the following common Open Web Application Security Project (OWASP) attacks: SQL injections, cross-site scripting (XSS), webshell uploads, backdoors, command injections, unauthorized HTTP requests, common vulnerabilities of web servers, unauthorized access to core files, path traversal, and scan attacks.

  • Hiding of origin IP addresses: WAF prevents origin IP addresses from being exposed. This prevents attackers from bypassing WAF to attack origin servers.

  • Timely updates of patches for zero-day vulnerabilities: WAF updates patches at the earliest opportunity to protect your websites.

  • User-friendly monitoring mode: You can enable this mode to monitor new website services. To help measure false positives, WAF sends an alert when suspicious traffic that matches specified protection rules is detected instead of blocking the traffic.

Precise protection

  • WAF can parse HTTP data in common formats. The HTTP data includes header, form, multipart, JSON, and XML data.

  • WAF can decode data that is encoded by using the following methods: URL encoding, JavaScript Unicode encoding, HEX encoding, HTML entity encoding, Java serialization, PHP serialization, Base64 encoding, UTF-7 encoding, UTF-8 encoding, and nested encoding.

  • WAF can preprocess data to provide more fine-grained and accurate data sources for detection engines at the upper layer. The preprocessing mechanisms include space compression, comment pruning, and special character processing.

  • WAF can detect complex data. WAF supports specific complexity in detection logic to prevent false positives that are caused by sensitive detection operations. WAF also supports adaptive decoding of data that is encoded in different formats to prevent bypassing.

Protection against HTTP flood attacks

  • WAF restricts the frequency of requests from a specific origin IP address by using various methods, such as CAPTCHA verification and redirection for authentication.

  • To protect against a large number of slow HTTP attacks, WAF executes precise protection rules based on statistical data, such as the distribution of status codes, distribution of requested URLs, and identification of abnormal HTTP Referer headers and User-Agent characteristics.

  • WAF takes full advantage of Alibaba Cloud big data security solutions to build analysis models for threat intelligence and trusted access. The models can be used to identify malicious requests.

Fine-grained access control

  • In the WAF console, you can combine different HTTP fields, such as the IP, URL, Referer, and User-Agent fields, to configure protection rules and implement fine-grained access control. You can also configure custom protection rules to provide protection in various scenarios, such as hotlink protection and website background protection.

  • This module can be used together with other security modules, such as web security and HTTP flood protection, to build a multi-layer protection architecture. This way, WAF can identify trusted and malicious traffic in a fine-grained manner.

Virtual patching

Before the patches for web application vulnerabilities are released or installed, you can adjust web protection rules to protect your services.

Attack event management

WAF allows you to manage attack events based on statistical data, such as attack events, attack traffic, and attack scales.

Flexibility and reliability

  • Load balancing: WAF can provide services in cluster mode. WAF uses multiple servers to balance loads and supports various scheduling algorithms.

  • Smooth and elastic scaling: You can add servers to or remove servers from a cluster to adjust the WAF service capability based on your business requirements.

  • Elimination of single points of failure (SPOFs): If a WAF node fails or is repaired, WAF can still provide services.

For more information, visit the product page of Web Application Firewall.




More than 10 years of web security experience

  • WAF is developed based on more than 10 years of web security experience of Alibaba Group and provides the same security experience as Tmall, Taobao, Alipay, and other well-known applications.

  • WAF provides a professional security team to help ensure the security of your services.

  • WAF defends against known OWASP vulnerabilities and constantly fixes and discloses vulnerabilities.

Protection against HTTP flood attacks and crawler attacks

  • WAF mitigates HTTP flood attacks.

  • WAF defends against web crawlers to prevent excessive network resource consumption.

  • WAF detects and blocks malicious requests that may affect availability, compromise response latency, or consume excessive resources, such as bandwidth, database, SMS, and API resources.

  • WAF allows you to configure custom protection rules for various business scenarios.

Integration with big data capabilities

  • WAF can defend against hundreds of millions of attacks every day.

  • WAF provides an IP address library that contains a large number of IP addresses.

  • WAF provides a wide range of use cases to help obtain the patterns, methods, and signatures of various common network attacks.

  • WAF is continuously integrated with advanced technologies for big data analytics.

Ease of use and reliability

  • You can activate and configure WAF within 5 minutes.

  • You do not need to install software or hardware or adjust routing configurations.

  • Protection clusters are used to prevent SPOFs and redundancy.

  • WAF provides high traffic processing performance.


WAF is suitable for all users on and outside Alibaba Cloud. WAF helps protect web applications in various industries such as finance, e-commerce, online-to-offline (O2O), Internet Plus, gaming, public services, and insurance.


You can add domain names or cloud service instances to WAF. You cannot add IP addresses to WAF.

How to use WAF

How to use WAF

For more information, see Get started with WAF 3.0.

Compliance certificates

WAF passed the following authoritative certifications: ISO 9001, ISO 20000, ISO 22301, ISO 27001, ISO 27017, ISO 27018, ISO 27701, ISO 29151, BS 10012, Cloud Security Alliance (CSA) STAR certification, Cybersecurity in China Multi-level Protection Scheme (MLPS 2.0) Level III, Service Organization Control (SOC) 1, 2, and 3, Cloud Computing Compliance Controls Catalog (C5), Green Finance Certification Scheme developed by Hong Kong Quality Assurance Agency (HKQAA), Outsourced Service Providers Audit Report (OSPAR), and Payment Card Industry Data Security Standard (PCI DSS).