msrbot: Robots.txt & Crawl Policy Reference

AI Summary: msrbot is a historical registry label associated with a Microsoft Research web crawler, but no exact User-Agent or operator-owned documentation was available in the current review. A headless Bing search returned only generic Microsoft/account pages and no verified crawler source. Treat matching traffic as unidentified until access logs and a current authoritative source establish its identity and policy.

Role and policy boundary

The inventory describes msrbot as a Microsoft Research web crawler, but provides no User-Agent value and links only to a community-maintained crawler registry. A headless Bing search for Microsoft Research web crawler msrbot official returned generic Microsoft and account pages, not a verified Microsoft Research crawler document. This is a source-discovery limitation, not evidence that the label never existed or that a client is inactive.

The Microsoft Research attribution and general crawling role are therefore historical registry claims only. A request may come from an old research deployment, an independent crawler, a test harness, a fork, or a spoofed header. Do not infer current activity, operator identity, downstream use, AI-training purpose, permission to crawl, or access to private content from the label.

Because the exact token is unknown, do not publish a made-up User-agent: msrbot group as if it will reliably match the client. If logs later reveal a complete and independently attributable header, use that exact value:

User-agent: CONFIRMED-OBSERVED-TOKEN
Disallow: /

For selective access after confirmation:

User-agent: CONFIRMED-OBSERVED-TOKEN
Allow: /public/
Allow: /docs/
Disallow: /admin/
Disallow: /account/
Disallow: /private/
Disallow: /research-data/
Disallow: /api/

These are defensive examples, not recovered Microsoft Research instructions. Robots.txt is advisory and cannot protect private or licensed content; use authentication, authorization, signed URLs, data minimization, and origin controls for those boundaries.

Layered verification

Begin with raw access logs and preserve the complete User-Agent, source IP, ASN, reverse-DNS result, HTTP method, requested path, response status, response size, redirect chain, timestamp, and request rate. No exact msrbot token or current operator source-verification procedure was available in this review. The community label is useful for search and triage only; it is not authentication.

Do not reuse current Bingbot or adidxbot verification procedures for msrbot without a current source that explicitly covers this label. A generic Microsoft domain, a Microsoft Research hostname, or a matching organization name does not prove that an observed request came from this crawler.

Compare observed behavior with a research-crawling hypothesis without turning it into attribution. Public HTML, metadata, datasets, papers, and feeds may be consistent with discovery. Private research notes, account routes, licensed documents, internal APIs, high concurrency, repeated retries, or unexpected bulk downloads may indicate spoofing, abuse, a partner integration, or another client. These observations establish impact and data risk, not operator identity or downstream use.

Evaluate /robots.txt only after the actual header is known. Confirm that it is served by the correct host, returns a successful status and text content type, and contains the exact group you intend to publish. Test the complete observed token, any confirmed Microsoft Research token, and the global group separately. Page-level directives can express discovery preferences:

<meta name="robots" content="noindex, nofollow">

X-Robots-Tag: noindex, nofollow

These signals do not authenticate an undocumented research client or secure private routes. Enforce sensitive boundaries in the application and at the origin.

WAF and Nginx remediation examples

When the identity is unknown, use a report-only candidate rule and do not block broad ms, research, or microsoft substrings. Adapt the expression to your WAF provider:

{
  "description": "Log unidentified Microsoft Research crawler candidates",
  "expression": "lower(http.user_agent) contains \"msrbot\"",
  "action": "log"
}

Once a complete token and authoritative source establish the identity, replace the candidate with a narrow route-scoped control:

map $http_user_agent $block_confirmed_msr_private {
    default 0;
    # Add only a complete, independently verified token here.
    # ~*Confirmed-MSRBot-Token 1;
}

server {
    location ~ ^/(admin|account|private|research-data|internal|api)/ {
        if ($block_confirmed_msr_private) { return 403; }
        try_files $uri $uri/ =404;
    }
}

Do not invent an IP allowlist, reverse-DNS suffix, or Microsoft verified-bot exception from a generic search result. A User-Agent match is easy to spoof and the candidate expression may catch unrelated clients. Test public pages, research datasets, feeds, sitemaps, licensed documents, accounts, APIs, and approved integrations separately. Pair edge controls with authentication, rate limits, signed assets, caching, data-loss monitoring, and anomaly detection.

Review checklist

Search logs for broad candidates only to locate a complete header, then preserve the exact value. Record source IP, ASN, PTR result, forward lookup, path, method, response size, status, timing, rate, and redirect chain. Check whether a current operator source identifies the client before assigning Microsoft Research ownership or a crawl purpose.

Re-check the community registry, Microsoft Research properties, and current Microsoft crawler documentation when a credible source becomes discoverable. Keep this profile at legacy-label and the User-Agent as Not publicly documented until a first-party source publishes a current token, purpose, source-verification method, rate guidance, or opt-out process. Treat the unsuccessful headless search as a source limitation, not proof of inactivity.

Decide whether your objective is to preserve public discovery, limit extraction, protect research materials, or reduce crawl load. Publish exact robots rules only after the token is known, and enforce private routes with application and WAF controls. Do not claim successful blocking from configuration alone; verify subsequent logs and response behavior.

The registry’s Microsoft Research label does not establish AI-model training use. Keep any downstream-use statement separate from the limited evidence available here.

References

1. Crawler User Agents community registry — registry source for the label; it does not provide an operator-owned msrbot policy or exact User-Agent in the current inventory.
2. Headless Bing search for msrbot — search returned generic Microsoft/account pages and no verified crawler source in the extracted results on 2026-08-25.
3. Microsoft Research — organization-level reference only; no msrbot policy was established from it in this review.
4. Google Robots.txt Introduction — general explanation of crawler directives and their limitations.
5. RFC 9309 — Robots Exclusion Protocol standard; it does not authenticate a User-Agent.

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