{"id":17673,"date":"2026-08-04T06:50:50","date_gmt":"2026-08-04T05:50:50","guid":{"rendered":"https:\/\/www.milesweb.co.uk\/hosting-faqs\/?p=17673"},"modified":"2026-08-04T06:50:51","modified_gmt":"2026-08-04T05:50:51","slug":"how-to-create-custom-waf-rules","status":"publish","type":"post","link":"https:\/\/www.milesweb.co.uk\/hosting-faqs\/how-to-create-custom-waf-rules\/","title":{"rendered":"How to Create Custom WAF Rules?"},"content":{"rendered":"\n

Default rule sets on most WAFs handle the obvious threats well, known SQL injection patterns, XSS payloads, and malicious bot signatures. What they miss is the traffic specific to your application: a login endpoint getting hit repeatedly from one IP range or a parameter in your API that keeps showing up with a payload nobody accounted for. That gap is precisely where a custom rule earns its place.<\/p>\n\n\n\n

Here’s how to build a custom Web Application Firewall<\/strong><\/a> rule and get it into production without disrupting real user traffic.<\/p>\n\n\n\n

Step 1: Find the Exact Request Causing Trouble<\/h3>\n\n\n\n

Pull the access logs, WAF alerts, or SIEM entries tied to the attack, and note the URI path, the specific header or parameter carrying the payload, and the source IP if there’s a clear pattern. A rule based on a vague memory of the attack almost always ends up too broad or too narrow once it hits live traffic.<\/p>\n\n\n\n

Step 2: Decide How the Rule Should Match<\/h3>\n\n\n\n

Most WAFs support a handful of match types: IP match, string match, regex, or size-based conditions. A regex match on the query string usually works well for catching injection attempts, while a straightforward IP match is faster and simpler for a known malicious actor. Also decide which part of the request you’re inspecting, the body, a header, or the query string, since that choice affects both accuracy and performance.<\/p>\n\n\n\n

Step 3: Choose What Happens When the Rule Matches<\/h3>\n\n\n\n

Every rule needs an action attached to it, typically block, allow, count, or a CAPTCHA challenge. New rules should always start in count mode. Every match is recorded here, and live traffic stays completely unaffected. Verify that the rule catches exactly what it’s supposed to before you switch it over to block mode.<\/p>\n\n\n\n

Step 4: Set the Rule Order Right<\/h3>\n\n\n\n

WAFs work through their rule list top to bottom, and a specific rule sitting after a broader one just won’t receive its turn. If the new rule is meant to take priority over an existing managed rule, move it higher up so it is evaluated first. <\/p>\n\n\n\n

Related Read<\/strong>: How to Configure WAF Rules for Maximum Security?<\/a><\/p>\n\n\n\n

Step 5: Test Against Real Traffic Before Turning It On<\/h3>\n\n\n\n

Keep the rule in count mode against live traffic for at least a few hours, longer if the application sees decent volume. Once that window closes, go through the match logs and pick out any legitimate requests that got caught by mistake.<\/p>\n\n\n\n

Step 6: Switch the Rule to Block<\/h3>\n\n\n\n

Once the logs back up the rule’s accuracy, flip the action from count to block or allow. The first few hours after switching the rule are crucial because production traffic can reveal edge cases that testing did not encounter.<\/p>\n\n\n\n

Step 7: Review the Rule Regularly<\/h3>\n\n\n\n

Attack patterns don’t stay still, and neither does legitimate traffic. Set a fixed schedule for pulling WAF logs, drop the rules that stopped catching anything useful, and update conditions as soon as a new attack variant shows up.<\/p>\n\n\n\n

This is how you build a custom WAF rule that actually holds up in production, backed by real log data, tested before enforcement, and reviewed often enough to stay useful.<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

Default rule sets on most WAFs handle the obvious threats well, known SQL injection patterns, XSS payloads, and malicious bot signatures. What they miss is the traffic specific to your application: a login endpoint getting hit repeatedly from one IP range or a parameter in your API that keeps showing up with a payload nobody […]<\/p>\n","protected":false},"author":35,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[867],"tags":[],"class_list":["post-17673","post","type-post","status-publish","format-standard","placeholder-for-hentry","category-firewall"],"yoast_head":"\nHow to Create Custom WAF Rules?<\/title>\n<meta name=\"description\" content=\"Learn how to create custom WAF rules to block threats, reduce false positives, and strengthen web application security with best practices.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/how-to-create-custom-waf-rules\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How to Create Custom WAF Rules?\" \/>\n<meta property=\"og:description\" content=\"Learn how to create custom WAF rules to block threats, reduce false positives, and strengthen web application security with best practices.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/how-to-create-custom-waf-rules\/\" \/>\n<meta property=\"og:site_name\" content=\"Web Hosting FAQs by MilesWeb\" \/>\n<meta property=\"article:published_time\" content=\"2026-08-04T05:50:50+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-08-04T05:50:51+00:00\" \/>\n<meta name=\"author\" content=\"Jackson Lane\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Jackson Lane\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/how-to-create-custom-waf-rules\/\",\"url\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/how-to-create-custom-waf-rules\/\",\"name\":\"How to Create Custom WAF Rules?\",\"isPartOf\":{\"@id\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/#website\"},\"datePublished\":\"2026-08-04T05:50:50+00:00\",\"dateModified\":\"2026-08-04T05:50:51+00:00\",\"author\":{\"@id\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/#\/schema\/person\/1f580bdff0fa81720fae0fd0c3919758\"},\"description\":\"Learn how to create custom WAF rules to block threats, reduce false positives, and strengthen web application security with best practices.\",\"breadcrumb\":{\"@id\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/how-to-create-custom-waf-rules\/#breadcrumb\"},\"inLanguage\":\"en-GB\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/how-to-create-custom-waf-rules\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/how-to-create-custom-waf-rules\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"How to Create Custom WAF Rules?\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/#website\",\"url\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/\",\"name\":\"Web Hosting FAQs by MilesWeb\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-GB\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/#\/schema\/person\/1f580bdff0fa81720fae0fd0c3919758\",\"name\":\"Jackson Lane\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-GB\",\"@id\":\"https:\/\/www.milesweb.co.uk\/hosting-faqs\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/dd43b6ec8f85bdee32ceaac59c48807f?s=96&d=blank&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/dd43b6ec8f85bdee32ceaac59c48807f?s=96&d=blank&r=g\",\"caption\":\"Jackson Lane\"},\"description\":\"I am an experienced Marketing Manager at MilesWeb UK, a leading web hosting company in the UK. 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