What is Netcraft?

Netcraft is a bot in the security scanners category, operated by Netcraft.

Bot name
Netcraft
Operator
Netcraft
Type
Bot
Respects robots.txt
Not confirmed
robots.txt user agent
Netcraft
Signs requests (Web Bot Auth)
No

About Netcraft

The Netcraft Survey Agent is a bot that analyzes web server technology stacks for their Web Server Survey.

Security scanners probe sites for vulnerabilities, certificates and exposed services. Some are research projects, some are vendors you hired. Allow your own scanners and block the rest at the WAF.

Netcraft user agent

Sample user agent strings sent by Netcraft:

  • Mozilla/5.0 (compatible; NetcraftSurveyAgent/1.0; [email protected])
  • Mozilla/4.0 (compatible; Netcraft Web Server Survey)

Anyone can copy a user agent string. Transfon Security also checks where each request comes from, so a request that claims to be a known crawler but comes from the wrong network is treated as a fake, not as the real crawler.

How to block Netcraft in robots.txt

We have not confirmed whether Netcraft follows robots.txt. Add a rule, then check your logs to see that it stopped. robots.txt is a plain text file at the root of your domain, such as https://example.com/robots.txt.

Block Netcraft from the whole site

User-agent: Netcraft
Disallow: /

Block Netcraft from some folders

User-agent: Netcraft
Disallow: /private/
Disallow: /search

Allow Netcraft only on some folders

User-agent: Netcraft
Allow: /blog/
Disallow: /

Allow Netcraft and block other crawlers

User-agent: Netcraft
Allow: /

User-agent: *
Disallow: /

Things to know

  • Each host needs its own file. Rules on www.example.com do not apply to shop.example.com.
  • A crawler obeys only the most specific group that names it. Once you add a User-agent: Netcraft group, Netcraft ignores your User-agent: * rules, so repeat any that should still apply.
  • The user agent name is not case sensitive. We take Netcraft from Netcraft's user agent; check Netcraft's own documentation if it publishes a different robots.txt name.
  • Crawlers cache robots.txt, so changes can take up to a day to apply. Disallow stops crawling but does not remove pages already collected or indexed.

Limits of robots.txt

  1. Netcraft may not follow the rule. robots.txt is a request that nothing enforces, and we have not confirmed that Netcraft follows it. Check your logs after adding a rule.
  2. The user agent could be fake. robots.txt matches the name a request claims. Anyone can send Netcraft's user agent, and a scraper using it is not bound by Netcraft's robots.txt policy. Only checking the source network tells a real Netcraft from a fake one.

Treat robots.txt as a statement of your policy, and enforce it where requests arrive.

Who should care about Netcraft

Publishers

Allow Netcraft if it is a service you use, and keep its visits out of page views and ad requests either way.

Transfon Security for publishers

Media buyers and advertisers

Netcraft is not a person. Exclude it from campaign and conversion data so reports reflect real visitors.

Transfon Security for advertisers

E-commerce

Allow Netcraft only if it works for your store, and keep it away from cart and checkout.

Transfon Security for e-commerce

SaaS and APIs

If Netcraft is a service you use, allow it on the endpoints it needs and block it elsewhere.

Transfon Security for SaaS and APIs

Block Netcraft with Transfon Security

robots.txt is a request, not an enforcement. Transfon Security shows Netcraft by name in the Top Bots report, so you can see how often it visits and which pages it reads. Block or allow it with a User Agent rule, or slow it down with a rate limit decision rule.

Transfon Security

Control Netcraft on your site

  • See every Netcraft visit and the pages it reads
  • Spot bots that fake trusted crawler names
  • Block, allow or rate limit Netcraft with one rule
  • Works with or without robots.txt support

Frequently asked questions

What is Netcraft?

Netcraft is a bot in the security scanners category, operated by Netcraft. The Netcraft Survey Agent is a bot that analyzes web server technology stacks for their Web Server Survey.

Does Netcraft respect robots.txt?

We have not confirmed whether Netcraft follows robots.txt. Add a robots.txt rule, then check your logs to see that it stopped, and block it by user agent if it did not.

How do I block Netcraft?

Add "User-agent: Netcraft" followed by "Disallow: /" to the robots.txt file at the root of your site. To enforce it, block requests whose user agent contains "Netcraft" at your WAF. In Transfon Security that is one User Agent block rule.

Is robots.txt enough to block Netcraft?

No. robots.txt is voluntary, so Netcraft may not follow it, and anyone can send Netcraft's user agent, so a fake Netcraft ignores your rule. Enforce the rule where requests arrive, at your WAF, and check the source network.

Should I block Netcraft?

Security scanners probe sites for vulnerabilities, certificates and exposed services. Some are research projects, some are vendors you hired. Allow your own scanners and block the rest at the WAF.

Related bots

All security scanners · Full bot directory

See Which Bots Visit Your Site

Transfon Security identifies every bot in this directory in your traffic reports, flags fake search crawlers, and lets you allow, block or rate limit each bot.

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