Amazon Route53 HealthCheck

Amazon Route 53 Health Check is AWS’s endpoint monitoring service. It sends recurring HTTP, HTTPS, or TCP requests to an endpoint configured by an AWS customer, then uses the result to determine whether that endpoint is healthy. Depending on the customer’s configuration, Route 53 can use the result for DNS failover, exclude an unhealthy resource from a routing policy, or expose the status through CloudWatch and related notifications.

This is not a search crawler or an AI crawler. An HTTP or HTTPS health check can request a specific path and, when configured, inspect the response status or search the response body for a configured string. That makes the request observable in application logs and relevant to bot-management controls.

Route 53 health checkers operate from multiple locations. A single logical health check can therefore produce similar requests from several AWS source IPs. Traffic can arrive in short bursts—up to several requests per second—followed by a period with no requests. The configured interval is not a reliable indicator of global request frequency.

For authentication, the strongest signal is the combination of the AWS-published health-check CIDR ranges, the configured checker regions, the expected path and protocol, the request cadence, and the health-check reference visible in logs. An AWS ASN or a user-agent match alone is not enough.

• Endpoint availability monitoring: Route 53 checks whether a web server, application endpoint, or other public resource is reachable and responding as expected.
• DNS failover: When a health check is associated with an applicable routing policy, Route 53 can stop returning an unhealthy resource and route queries to a healthy alternative.
• CloudWatch alerting: Health-check status and latency-related metrics can be monitored in CloudWatch, with alarms and SNS notifications configured for operational response.
• Calculated health checks: A parent health check can combine the status of other health checks, which is useful when availability depends on several resources.
• Regional performance monitoring: Customers can measure connection and response latency between Route 53 health-checker locations and an endpoint.

Route 53 health checks are legitimate infrastructure traffic, but their identity can still be imitated. The user-agent is easy to copy, and a request that advertises itself as a Route 53 health check does not prove that it came from AWS.

Potentially suspicious patterns include:

• User-agent spoofing: Requests using a Route 53 health-check string but originating outside the current AWS health-check ranges should not be trusted.
• Reconnaissance disguised as monitoring: An attacker may imitate a familiar health-check pattern to probe a publicly exposed health endpoint or learn how the endpoint responds.
• Targeted load on a health endpoint: A poorly designed health endpoint may trigger expensive database or dependency checks. Repeated traffic that imitates monitoring can then create unnecessary load.
• Overbroad allowlisting: Allowing every request to a path because it resembles a health-check endpoint can expose a route that should be limited to verified infrastructure traffic.
• Stale or misconfigured checks: An old check can continue generating traffic against a deprecated, redirected, or unexpectedly expensive endpoint.

Spoofed requests do not change the real Route 53 health status or trigger AWS DNS failover. Route 53 makes routing decisions from its own checker fleet. The impact is instead local to the monitored environment, such as extra load, noisy logs, exposed endpoint behavior, or a bypass of an under-specified allowlist.

If your team configured a Route 53 health check against a domain, subdomain, or public IP address, the requests are expected. Common explanations include:

• Several source IPs: Route 53 uses health checkers in the global range and in the AWS Regions selected when the check was created.
• Short bursts: Independent checker locations can send requests close together, even when the configured interval is 10 or 30 seconds.
• A stale configuration: An unused check may still point to an old hostname, IP address, redirect, or application path.
• A third-party configuration: If the request is not associated with your AWS account, another operator may have configured a check against your public endpoint, or the traffic may be an imitation.

This traffic is not crawling your site for content, but it can still affect application logs, rate limits, WAF rules, and the performance of an expensive health endpoint.

1. Inspect the user-agent, but do not trust it alone. Look for a Route 53 health-check pattern and, when present, the reference ID. Treat it as a classification clue, not proof of identity.
2. Validate the source IP. Compare the request against the current ROUTE53_HEALTHCHECKS entries in AWS’s ip-ranges.json. Do not allow the broader AMAZON service ranges when a narrower health-check range is available.
3. Include the right ranges. AWS recommends allowing the global range and all ranges for the AWS Regions selected for the health check. The source IP can change within those ranges.
4. Use AWS-managed prefix lists where available. For supported AWS security groups, use the regional com.amazonaws.<region>.route53-healthchecks prefix list. For IPv6 health checks, also allow the corresponding ipv6.route53-healthchecks prefix list.
5. Cross-check your Route 53 configuration. Confirm the health-check ID, target hostname or IP, path, port, protocol, selected regions, interval, and failure threshold.
6. Check behavior over time. Genuine checks are narrow and repetitive. Varying paths, session-like behavior, cookies, unexpected redirects, or irregular high-volume traffic are inconsistent with a normal health check.
7. Treat ASN and reverse DNS as supporting signals. They can help with investigation, but IP-range validation and configuration matching are stronger controls.

Do not block a verified Route 53 health check by default. Blocking it can make Route 53 mark a healthy endpoint as unhealthy, trigger false alerts, or remove a resource from DNS routing. The operational risk is greater than with a search crawler because the check may be part of the site’s availability and failover design

.

Blocking or restricting the traffic makes sense when:

• the health check is obsolete or points to the wrong resource;
• the endpoint is generating excessive cost or application load;
• the traffic claims to be Route 53 but fails IP-range or configuration validation; or
• the endpoint should only accept checks from a known set of checker ranges.

If the check belongs to your account, update or delete it in Route 53. If it does not, first confirm that the traffic is not required by a customer, partner, or other owner of the endpoint. Then apply a narrow control to the source ranges or endpoint, rather than blocking broad AWS traffic.

• Use a dedicated endpoint.Point the check to a lightweight, read-only path that performs only the checks needed to establish availability. Avoid an endpoint that triggers expensive queries, state changes, authentication flows, or redirects.
• Scope allowlisting to the health path. Permit current ROUTE53_HEALTHCHECKS ranges only on the dedicated endpoint, not across the entire site or API.
• Automate IP-range updates. AWS says health-check ranges are rarely changed, but they should still be refreshed from ip-ranges.json rather than hardcoded permanently.
• Prefer prefix lists for AWS security groups. This reduces manual CIDR maintenance where AWS-managed prefix lists are supported.
• Use rate limiting carefully. A rate limit can be a backstop against duplicated or abusive traffic, but it must allow for multiple checker locations and the configured 10- or 30-second interval. Test the limit against the real health-check pattern before enforcing it.
• Alert on anomalies. Alert on requests outside the published ranges, unexpected paths, abnormal volume, or a mismatch with the Route 53 configuration. Do not alert on the presence of multiple AWS source IPs alone.

Illustrative Nginx configuration:

location = /health-check {
# Replace these placeholders with the current ROUTE53_HEALTHCHECKS ranges
# for the global range and the Regions selected in Route 53.
allow <current-route53-healthcheck-cidr-1>;
allow <current-route53-healthcheck-cidr-2>;
deny all;
}

Treat Amazon Route 53 Health Check as legitimate Technical Partner traffic only after its identity and behavior have been verified. A user-agent-only rule is not sufficient. The safer model is to combine source-IP validation, the observed request pattern, and the customer’s Route 53 configuration, then scope the resulting authorization or rate limit to the relevant endpoint.