Overrides

When Cloudflare's DDoS Protection systems detect an attack, mitigations are emitted against it. Each mitigation has a single managed rule from the managed ruleset associated with it.

All mitigations and its associated managed rules are evaluated in order by DDoS Protection systems one by one.

You can create only one override ruleset that can contain one or multiple override rules. An override rule instructs the DDoS Protection system on the action it should take based on its matching managed rule.

For each active mitigation that is linked to a single managed rule, Cloudflare will go through all of the override rules defined in the override ruleset until one matches the managed rule, and apply the action and stop at that point. Otherwise, evaluation will continue in order until a rule matches.

However, within an override rule, specificity matters. If the override rule has the following two elements defined, then DDoS Protection systems will prioritize specificity when evaluating overrides:

• All of the managed rules in the ruleset are set to a specific action.
• A managed rule within that ruleset is set to a different action from the rest of the rules.

Examples

General example

A managed ruleset contains the following managed rules:

• Managed rule 1
• Managed rule 2
• Managed rule 3

An override ruleset contains the following override rules:

• Override rule 1
  • Managed rule 1 is set to block
• Override rule 2
  • All managed rules are set to challenge
  • Managed rule 1 is set to log
  • Managed rule 2 is set to log
• Override rule 3
  • Managed rule 3 is set to log

If DDoS Protection triggers three mitigations — one linked with an individual managed rule — then the override for each mitigation is evaluated one by one.

Mitigation 1 linked with managed rule 1

Since managed rule 1 matches override rule 1, Cloudflare will block the attacks and not proceed with the rest of the rules.

Mitigation 2 linked with managed rule 2

Since managed rule 2 does not match override rule 1, Cloudflare will proceed to override rule 2.

Override rule 2 matches both All managed rules and managed rule 2, but specificity takes precedent. It does not challenge as dictated by All managed rules and instead proceeds with log since it matches the most specific managed rule.

Mitigation 3 linked with managed rule 3

Since managed rule 3 does not match override rule 1, Cloudflare will proceed to override rule 2.

Override rule 2 sets All managed rules to challenge, so Cloudflare challenges the attack and does not proceed to override rule 3.

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Sensitivity example

An additional dimension to take into account is Cloudflare will apply a given Override Rule only if its conditions are met, which includes the Sensitivity level.

While the override rule needs to match and modify the correct managed rule (or all managed rules in the case of mitigation 3 above), it also has to meet the specified Sensitivity level of the rule.

• Override rule 1

  • All managed rules are set to challenge at low sensitivity

• Override rule 2

  • Managed rule 1 is set to log at default sensitivity.

Scenario: You receive a small attack below the threshold for low sensitivity, but above the threshold for high sensitivity on managed rule 1.

• Override rule 1 does not meet the low sensitivity threshold. Therefore, we do not match the override and do not mitigate the attack, but proceed to evaluate the next managed rule in case the override rules instruct DDoS Protection to mitigate.
• Override rule 2 sets log at default visibility, which matches the condition, so the defined action is applied and attack traffic is logged.