Recommended Free Tools
iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
A scraper block may be related to the network behind its source IP, not just to its headers—but the title’s either-or claim goes too far. Detection systems can combine network reputation with request behavior, headers, and browser or session signals. Only the affected site’s logs and rule configuration can show which factor actually triggered a particular block.
What an ASN tells a detection system
An autonomous system number (ASN) identifies the network associated with an IP address. It can provide a network-level signal, but it does not prove that an individual request—or every user on that network—is automated or abusive.
Sites may use an ASN as one input among several. Cloudflare documents scraping detections that dynamically analyze request patterns by ASN and behavior by JA4 fingerprint, a TLS-level fingerprint. Its materials also describe other request and browser signals. A block therefore cannot be diagnosed from the ASN or headers alone. Cloudflare’s scraping detection documentation explains the ASN- and JA4-based detections. Cloudflare says these matches are recalculated dynamically rather than permanently attached to a fingerprint when suspicious behavior stops.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Why changing headers may not change the outcome
A User-Agent or other header is only part of a request’s observable characteristics. Cloudflare’s guidance on false bot detection describes checking a bot-like User-Agent against the request source, including verification mechanisms such as reverse DNS or IP validation. A plausible-looking User-Agent does not establish that the source is the expected bot.
#1 Best Overall
That does not mean headers never matter. It means changing them alone is not a dependable diagnostic or remedy: the decision may depend on the source network, request pattern, fingerprint, or session signals as well. Cloudflare’s examples include legitimate Google Cloud services and monitoring tools whose source ranges do not match the ranges expected for the bot they resemble. Cloudflare’s false bot detection guidance describes the verification issue and a narrow exception approach.
How to distinguish a network signal from a header problem
These checks help narrow the possibilities; they are diagnostic questions, not proof of what a particular site’s system did. Keep the request behavior as similar as practical and compare the evidence available to you.
- Check whether impact follows the source network. If the same IP or network is consistently affected, while similar requests from another authorized network are treated differently, a network-level signal is plausible. It is not conclusive without the site’s telemetry.
- Look for changes across networks. If the outcome changes when the network changes but request behavior stays similar, that supports investigating network reputation alongside headers. Do not treat changing networks as a way to evade a site’s controls; follow its terms and use authorized access routes.
- Review the evidence the site exposes. For site operators, inspect the matched rule, challenge result, bot score, fingerprint information, and request logs if available. A response page alone may not reveal the decision path.
- Ask whether other users on the same provider are affected. A shared-network pattern can help identify a provider-level false positive, but does not show that every user behind that provider is a bot.
Cloudflare documents custom rules using ip.src.asnum, including examples that combine ASN with bot score. Its documentation says ip.src.asnum is available on all plans, while the illustrated bot-score field requires Enterprise Bot Management access; plan availability can change, so verify the current documentation. Cloudflare’s custom-rule examples show how these signals can be combined.
Free tools Windows power users keep installed
One-click scans. No signup required.
What an ASN-based signal can—and cannot—identify
An ASN signal may identify an intermediary network rather than the end client. AWS WAF describes ASN as an aggregation key derived from the source IP. When traffic reaches a protected service through a proxy or load balancer, that source can be the last proxy’s network, not the originating user’s.
Do not assume that a forwarded-IP header is equivalent to the network metadata derived from the connection peer. AWS separately cautions that forwarded-IP headers may be handled inconsistently or modified. A site operator should understand which source address a rule actually evaluates and whether any intermediary is trusted before drawing conclusions. See the AWS WAF developer guide’s rate-rule aggregation options.
Broad network blocks also carry false-positive risk. Cloudflare warns that blocking broad IP ranges can affect legitimate residential users, including people whose traffic is routed through intermediary networks. An ASN can be useful evidence, but treating every request associated with it as abusive can deny legitimate access. Cloudflare’s discussion of residential-proxy detection describes this challenge.
Quick Recap
Best Value
How site operators can investigate without weakening protection
- Identify the exact decision. Find the matched rule or managed rule, the action taken, and the request details available in security events. Avoid inferring a cause from a generic block page.
- Check the address and network context. Determine whether the evaluated IP belongs to the client or to a proxy or load balancer. Confirm how trusted forwarded-IP information is configured rather than treating arbitrary forwarded headers as authoritative.
- Correlate signals. Compare ASN with request behavior, bot score where available, fingerprint or session evidence, and the rule’s own conditions. An ASN match by itself is not proof of automation.
- Use a narrow exception only when justified. If a legitimate service is falsely identified, scope an exception to known request characteristics and place it before the blocking managed ruleset where the platform requires that order. Cloudflare’s false-positive guidance recommends a narrowly targeted exception; skipping security rules broadly can create risk.
- Reassess after the change. Confirm that legitimate requests now pass and that the exception does not admit unrelated traffic. Keep the rule limited to the verified source and behavior.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
