AWS Shield Advanced is embracing the AWS WAF Anti-DDoS managed rule group: What changes and how to prepare

July 29, 2026: We’ve updated this post to clarify the AWS Firewall Manager migration path.

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Application-layer distributed denial of service (DDoS) attacks are difficult to detect because they closely resemble legitimate traffic. HTTP request floods are now among the most common vectors targeting web applications, using valid-looking requests that blend in with normal user activity.

In June 2025, AWS launched the AWS WAF Anti-DDoS managed rule group, built specifically for application-layer (L7) DDoS protection. AWS Shield Advanced is adopting it as the default application-layer protection, and in time as the only one. On July 27, AWS Shield Advanced begins adding the Anti-DDoS managed rule group to eligible web access control lists (ACLs) in Count mode. It will not cause any interruption to your traffic alongside your existing L7 automatic mitigation and WAF rules. In this blog post, we provide details regarding the Anti-DDoS managed rule group and when the change is expected to reach your web ACLs. You will understand the phases and steps that you need to take before the finish date, including how the monitoring and metrics will change.

The Anti-DDoS managed rule group builds on what Shield Advanced automatic mitigation already provides. It profiles your traffic, learns what normal traffic looks like for your application, and establishes a baseline in minutes rather than hours. When an attack starts, it reacts within seconds and there are no health checks to configure. The rule group adds a Challenge action to the Block and Count actions you already use. Challenge decisions are driven by the AMR labels that mark the suspicion level of each inspected request. One option is a silent browser challenge, which has a background verification that runs in the visitor’s browser with no interstitial page, so legitimate users are never interrupted while automated traffic is filtered out. You can also exclude workload paths that don’t support Challenge, which fall back to Block mitigations instead. Sensitivity is configurable to Low, Medium, or High, and you set it separately for Block and Challenge. Block and Challenge are tuned independently; meaning you can run Challenge at high sensitivity to catch more suspicious traffic while keeping Block low to avoid dropping legitimate requests or reverse it for a stricter posture.

The rest is about cost and visibility:

• It uses less capacity than before. The rule group needs 50 web ACL capacity units (WCUs), down from the 150 the previous protection required, providing you with capacity for the rest of your rules.
• The dashboard ships in the AWS Management Console for AWS WAF. It’s there now, showing live DDoS events, match metrics, and the top URIs, geographies, and IP addresses driving traffic.
• It labels everything it inspects. Requests get labels for event-detected, graduated suspicion levels, and specific rules. Match on those labels in your own AWS WAF rules when you need logic the rule group doesn’t cover.
• You don’t pay for the attack traffic. During active mitigation, blocked DDoS requests drop out of your monthly count. That exclusion covers AWS WAF request fees, Anti-DDoS managed rule group request fees, and Shield Advanced request charges.

AWS Shield Advanced isn’t required to use any of these features. Shield Advanced subscribers get the rule group included with AWS WAF and any customer can turn it on independently. See AWS WAF pricing for more information on costs.

Shield Advanced upgrades application-layer DDoS protection in five phases. The following dates are when AWS will act automatically, not the earliest date when you can act. After the rule group is deployed in Count mode on July 27, 2026, you can begin migrating right away rather than waiting for the October auto-upgrade. There’s no window where protection lapses. Your current automatic mitigation stays active through every phase until the Anti-DDoS managed rule group takes over. That handoff happens in a single operation, with no cutover window and no gap for your traffic flows.

AWS adds the Anti-DDoS managed rule group in Count mode to every web ACL eligible for this rollout. Eligible means any Shield Advanced web ACL with at least one resource using application-layer automatic mitigation that isn’t already running the Anti-DDoS rule group. This is a broader set than the web ACLs eligible for the October auto-upgrade (Phase 3), which applies a stricter test. The deployment rolls out gradually, starting July 27 and expected to finish by August 7, 2026, so different web ACLs might be updated on different days. There’s no impact to your traffic because the rule group watches and labels requests without acting on them while your existing automatic mitigation keeps running. Throughout the evaluation period, you receive DDoS events, metrics, and AWS WAF labels at no additional charge.

The existing automatic mitigation and the Anti-DDoS managed rule group run side by side each detecting independently. Automatic mitigation continues to protect your resources while the rule group operates in Count mode. To compare their detection results, use the DDoSAttackRequests metric, AWS WAF labels, and the Anti-DDoS dashboard. All Anti-DDoS managed rule group charges are waived during this period, including the subscription fee, per-request fees, and WCU consumption costs for the eligible web ACLs from phase 1.

For eligible web ACLs, the auto-upgrade mirrors your existing automatic mitigation configuration. The rule group inherits your current setting, so a Block configuration comes up in Block mode and a Count configuration comes up in Count mode in a single, atomic operation. The rule group takes over in the same step that disables automatic mitigation, so protection never drops for an instant. This is a handoff rather than a cutover with no window where your resources are unprotected. If you’d rather not upgrade you can opt out by contacting AWS Support before the auto-upgrade date.

You don’t have to wait for the October auto-upgrade to migrate. As soon as the rule group is deployed in Count mode between July 27 and August 7, 2026, you can move to it on your own schedule. This is the path to use for web ACLs that aren’t eligible for the Phase 3 auto-upgrade, meaning mixed-mode web ACLs or ones with resources that don’t have automatic mitigation enabled. Work with your AWS account team and AWS Support at any point in this window to plan and complete the migration. Eligible web ACLs are also upgraded automatically starting October 1 (Phase 3), so guided migration is mainly for the web ACLs the auto-upgrade can’t cover.

As of January 1, 2027, the Shield Advanced application-layer automatic mitigation feature will no longer be available. Resources that haven’t migrated to the Anti-DDoS managed rule group will lose automatic application-layer DDoS mitigation.

Capability	Shield Advanced application layer automatic mitigation	Anti-DDoS managed rule group (AWSManagedRulesAntiDDoSRuleSet)
Feature type	Shield Advanced automatic mitigation	AWS WAF managed rule group
Detection and mitigation speed	Requires a baseline period; mitigation varies per event	Enhanced detection and faster mitigation Key Takeaways July 29, 2026: We’ve updated This to clarify the AWS Firewall Manager migration path. Application-layer distributed denial of service (DDoS) attacks are difficult to detect because they closely resemble legitimate traffic. HTTP request floods are now among the most common vectors targeting web applications, using valid-looking requests that blend in with normal user acti. ☕ Buy a Coffee