Report: retired 'msnbot' observed crawling a site in 2026 after adding a bingbot noarchive tag

TL;DR in plain English

• A Hacker News user reported that after adding a meta tag to stop Bing from archiving pages, requests from a user-agent string "msnbot" began hitting their site heavily; the poster verified the source IPs as belonging to Microsoft ranges: https://news.ycombinator.com/item?id=49320686
• msnbot was retired about 10 years ago and replaced by bingbot; its sudden reappearance in 2026 is unexplained in the report: https://news.ycombinator.com/item?id=49320686
• Immediate short actions: preserve raw logs, export a simple CSV of suspected hits, and apply emergency edge throttles or challenge rules while you investigate: https://news.ycombinator.com/item?id=49320686

A single first‑hand report is the source for the observations summarized here; treat this as an incident template and verify against your own logs before escalation: https://news.ycombinator.com/item?id=49320686

What changed

• The poster added to discourage Bing archiving; within a short window (the report says this began about a month ago relative to the post) requests labeled "msnbot" began fetching many pages in sequence: https://news.ycombinator.com/item?id=49320686
• The poster verified source IP addresses and found them in Microsoft-owned address space; they report the behavior as unexpected because msnbot was retired roughly 10 years ago and replaced by bingbot: https://news.ycombinator.com/item?id=49320686
• Capture priority: preserve raw access logs and any evidence of rdns/ASN lookups the poster used for verification: https://news.ycombinator.com/item?id=49320686

Why this matters (for real teams)

• Collection pattern: the poster believes the request pattern resembles automated dataset-style indexing more than a standard, polite search-engine crawl; that raises reuse and consent questions for content producers: https://news.ycombinator.com/item?id=49320686
• Surface risk: aggressive, sequential crawls can surface low-link or staging pages you did not intend to leave public, increasing the chance those URLs enter external datasets: https://news.ycombinator.com/item?id=49320686
• Operational impact: sustained crawling can raise bandwidth use and add latency; the reporter relied on rdns/asn checks before deciding whether to escalate to the provider: https://news.ycombinator.com/item?id=49320686

Concrete example: what this looks like in practice

• Sequence from the report: add a no-archive meta tag; shortly after, logs show frequent "msnbot" hits; reverse DNS and ASN lookups associate the IPs with Microsoft address ranges: https://news.ycombinator.com/item?id=49320686

• Quick verification steps (10–30 minutes):

  • Search access logs for the string "msnbot" and list top IPs by count; save the raw lines around spike times. Link for context: https://news.ycombinator.com/item?id=49320686
  • Run reverse DNS and whois/ASN checks on the top IPs and save outputs as evidence.
  • Produce a short incident note with timestamps and top counts for triage.

• Fast defensive measures you can apply in minutes:

  • Apply an emergency edge/CDN rule to challenge or throttle excessive requests from single IPs or from the UA string seen in your logs.
  • Use robots.txt or meta directives to declare intent for crawlers (compliance is voluntary, but it documents your request).
  • If the rdns/asn checks indicate Microsoft ownership and the crawl touches sensitive pages, prepare to open a provider abuse/support ticket with logs and lookup outputs: https://news.ycombinator.com/item?id=49320686

What small teams and solo founders should do now

Follow this concise, ordered checklist tailored for a 1–3 person team.

1. Preserve evidence (10–60 minutes)

• Save raw access logs that cover the last 7–14 days to separate, immutable storage. Reference: https://news.ycombinator.com/item?id=49320686
• Export a minimal parsed CSV with columns timestamp, IP, user-agent, path, bytes and attach it to an incident note.

2. Quick verification (10–30 minutes)

• Search logs/CSV for "msnbot" and closely related UA strings; record top IPs and request counts. The original poster used rdns/asn checks to verify ownership: https://news.ycombinator.com/item?id=49320686
• Run rdns and whois/ASN lookups on the top 10 IPs and save screenshots or text output.

3. Short-term mitigation (minutes to hours)

• Add an emergency edge/CDN rule to slow or challenge requests from the offending IPs or UA. This buys breathing room without cutting all traffic.
• Add a robots.txt disallow for sensitive paths, and for particularly sensitive endpoints consider short-term access restrictions (HTTP auth or IP allowlists) if feasible.
• If verification shows Microsoft-owned ranges and sensitive content was accessed, prepare an abuse/support ticket with the CSV and log extracts: https://news.ycombinator.com/item?id=49320686

4. Record and decide (same day)

• Write a one-page decision memo with totals: total requests, unique IPs, GB transferred, unique URLs touched, and the timespan analyzed. Keep this with the preserved artifacts.

Regional lens (UK)

• If the scraped pages may include UK personal data, preserve raw logs and the parsed CSV for at least 30 days in case the ICO requests them; the report shows the poster used rdns/asn verification to trace ownership: https://news.ycombinator.com/item?id=49320686
• Practical UK steps:
  • Timestamp your preservation steps and include counts (requests, GB, unique pages) in the incident note.
  • If the dataset likely contains personal data, consult legal counsel before taking purely technical-only steps.
• Suggested artifacts to keep: raw logs (14–30 days) and a one-page incident note with key counts and timestamps: https://news.ycombinator.com/item?id=49320686

US, UK, FR comparison

| Jurisdiction | Short action | When to notify regulator | |---|---:|---| | US | Prioritize provider support and contractual remedies; preserve logs | Notify per sector/state rules after assessing data impact | | UK | Preserve logs; assess personal-data exposure; consider ICO contact | If personal data likely exposed or impact is high | | FR | Preserve logs; prepare for faster regulator engagement (CNIL) | Quicker notification likely if personal data is involved |

When contacting provider support or regulators, include rdns/asn verification output and your CSV export as evidence; the Hacker News report uses these artifacts for escalation: https://news.ycombinator.com/item?id=49320686

Technical notes + this-week checklist

Assumptions / Hypotheses

• Hypothesis A: the crawler identifying as "msnbot" is operating from Microsoft-owned IPs, per the reporter’s rdns/asn checks reported here: https://news.ycombinator.com/item?id=49320686
• Hypothesis B: the access pattern—many contiguous pages fetched quickly—appears similar to automated dataset capture rather than a polite search crawl, according to the poster: https://news.ycombinator.com/item?id=49320686
• Operational thresholds (examples to tune for your site; these are assumptions for triage):
  • Rate threshold: 30–50 requests/second from a single source.
  • Per-IP spike: 100 requests/min.
  • Bandwidth trigger: >1 GB/hour or >10 GB/day from a single UA/IP cluster.
  • Traffic share: >5% of total site traffic from one UA.
  • Latency concern: median latency >100 ms or 5xx rate >1% may justify escalation.
  • Retention: keep preserved logs for 14–30 days; keep parsed exports for 90 days.
  • Example counts to illustrate incidents for escalation: 10,000 requests; 20 unique IPs; 12 GB transferred; 3,500 unique URLs.
  • Token example for API rate-limits: 2,048 tokens per-minute bucket (if you rate-limit by tokens).
  • Cost example trigger: $100/month increase in bandwidth spend may justify further investigation.

Risks / Mitigations

• Risk: unexpected bandwidth and cost. Mitigation: enable billing alerts, add short-term edge throttles, and preserve logs for billing reconciliation.
• Risk: scraping of non-public pages or personal data. Mitigation: export CSV of affected URLs and consult legal or the local regulator (ICO for UK, CNIL for France) if exposure looks likely: https://news.ycombinator.com/item?id=49320686
• Risk: user-agent spoofing or relayed traffic. Mitigation: verify ownership with rdns/asn checks and do not rely solely on UA strings; collect multiple data points before escalation: https://news.ycombinator.com/item?id=49320686

Next steps

Short-term (0–24h)

• [ ] Freeze the last 14 days of raw logs and back them up.
• [ ] Produce parsed CSV (timestamp, ip, ua, path, bytes) for suspected msnbot requests.
• [ ] Apply an emergency edge rule to slow or challenge high-volume requests.

Near-term (24–72h)

• [ ] Run reverse DNS and ASN checks for the top 20 IPs; save outputs.
• [ ] If Microsoft ASN is verified and impact is material against your thresholds, open a Microsoft abuse/support ticket and attach CSV + logs: https://news.ycombinator.com/item?id=49320686
• [ ] Monitor site latency and error rates; escalate if median latency >100 ms or 5xx rate increases materially.

Methodology note: this summary is based on a single Hacker News first‑hand report and standard triage practices; verify all findings against your own logs before taking irreversible actions: https://news.ycombinator.com/item?id=49320686

Report: retired 'msnbot' observed crawling a site in 2026 after adding a bingbot noarchive tag

An operator reports the long-retired 'msnbot' began heavy crawling after adding a bingbot noarchive meta tag. IPs trace to Microsoft and the pattern looks like…

https://aisignals.dev/posts/2026-08-31-report-retired-msnbot-observed-crawling-a-site-in-2026-after-adding-a-bingbot-noarchive-tag

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