Sergei Poljanski
5860cbee9a
Everything was hardcoded for one deployment: hostname in mail subjects, recipient address, log path, and a router name of "forgejo@docker" that also appeared inside the user-agent regex. That last one fails silently rather than loudly - on any instance whose Traefik router is named something else, the regex matches nothing, every user-agent is dropped, and the report claims zero bot traffic instead of erroring. Move configuration to environment variables read from /etc/crawler-alert.env, with defaults that suit a plain Traefik host. Only CRAWLER_RECIPIENT is required, and the script now refuses to run without it rather than mailing into the void. Anchor the user-agent regex on the request counter instead of the router name. SMTP can now be configured directly via CRAWLER_SMTP_*, so the tool no longer requires Forgejo in Docker; borrowing credentials from app.ini stays the default since it avoids a second copy of the password. Unauthenticated and non-TLS local relays are handled. Document the Traefik access log configuration in traefik-accesslog.yml. This is the one real prerequisite: Traefik drops all headers by default, so without an explicit User-Agent: keep there is nothing to analyse. Includes the field layout the parser expects, logrotate config, and the forwardedHeaders setup needed to recover real client IPs from behind Cloudflare. Rewrite README for someone arriving without context, and add a 0BSD LICENSE so the code can actually be reused. Assisted-by: Claude:opus-5
6.9 KiB
crawler-alert
Tells you which AI crawlers are really visiting your site, and which are lying about it.
Reads a Traefik access log, mails a threshold alert daily and a summary
weekly. Every bot is checked against its vendor's published IP ranges,
so a forged User-Agent does not get counted as the real thing.
Python 3.9+, standard library only. No database, no daemon, no agent.
Why user-agent alone is not enough
A User-Agent header is a string the client chooses. Anyone can send
ClaudeBot/1.0. On the Forgejo instance this was written for, measured
over 2.27M requests between November 2025 and August 2026:
| Bot | Claimed | Verified | Forged |
|---|---|---|---|
| Claude-User | 5,000 | 0 | 4,992 |
| ChatGPT-User | 2,670 | 13 | 2,657 |
| PerplexityBot | 2,038 | 0 | 846 |
| ClaudeBot | 4,301 | 1,070 | 852 |
| Google-Extended | 879 | 0 | 747 |
| GPTBot | 1,864 | 766 | 1,098 |
About 83% of AI-labelled traffic was not from the vendor it named.
The forgeries shared infrastructure: roughly 100 Google Cloud hosts
rotating through six vendor identities, sometimes within the same hour.
Their requests went to /.env, /terraform.tfstate,
/serviceAccountKey.json, /.env.prod.bak — credential harvesting
wearing a crawler's name.
The genuine crawlers behaved completely differently: 2,682 requests,
zero robots.txt violations, no repository source fetched, ~125 MB
total. Mostly they re-read robots.txt and sitemap.xml.
That gap is the point. Counting by user-agent tells you AI crawlers are hammering your server. Counting by verified IP tells you they are not, and that something else is — which is a different problem with a different fix.
How verification works
Most major vendors publish their crawler IP ranges as JSON. A request counts as legitimate only when its source address falls inside the range list belonging to the vendor its user-agent names.
| Vendor | Endpoint |
|---|---|
| OpenAI | openai.com/{chatgpt-user,gptbot,searchbot}.json |
| Anthropic | claude.com/crawling/bots.json |
developers.google.com/static/crawling/ipranges/*.json |
|
| Perplexity | perplexity.ai/perplexitybot.json |
| Apple | search.developer.apple.com/applebot.json |
Meta, ByteDance, Amazon, Diffbot, Cohere and Common Crawl publish no range file. Their traffic is reported but cannot be verified this way; Amazon supports reverse-DNS verification instead, which this script does not currently implement.
Ranges are fetched at run time and cached. If a vendor endpoint is unreachable the script falls back to the cache and says so in the mail, so an outage degrades the report instead of breaking it.
Requirements
- Traefik writing an access log with the User-Agent header kept —
it is dropped by default. See
traefik-accesslog.yml; without it nothing here works. - Python 3.9+
- An SMTP account, or a Forgejo/Gitea container whose
app.ini[mailer]section the script can borrow credentials from.
Install
sudo install -m755 crawler-alert.py /usr/local/bin/
sudo cp crawler-alert.env.example /etc/crawler-alert.env
sudo editor /etc/crawler-alert.env # set CRAWLER_RECIPIENT
sudo cp crawler-*.service crawler-*.timer /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now crawler-alert.timer crawler-weekly.timer
Check it against your own log before enabling the timers:
CRAWLER_LOG='/var/log/traefik/access.log*' crawler-alert.py --weekly --dry-run
--dry-run prints the mail instead of sending it and needs no SMTP
config, so it is safe to run repeatedly while you tune things.
Configuration
All settings are environment variables, read from
/etc/crawler-alert.env by the systemd units. Only CRAWLER_RECIPIENT
has no default.
| Variable | Default | Meaning |
|---|---|---|
CRAWLER_RECIPIENT |
(required) | Where reports are mailed |
CRAWLER_SITE |
this site |
Name shown in subject/header |
CRAWLER_LOG |
/var/log/traefik/access.log* |
Log glob |
CRAWLER_ROUTER |
(empty) | Traefik router to count, e.g. forgejo@docker. Empty counts everything |
CRAWLER_THRESHOLD |
100000 |
Daily alert fires above this |
CRAWLER_CACHE |
/var/cache/crawler-alert/ranges.json |
Cached ranges |
CRAWLER_MAIL_CONTAINER |
forgejo |
Container to read SMTP from |
CRAWLER_MAIL_INI |
/data/gitea/conf/app.ini |
Path inside it |
CRAWLER_SMTP_* |
(unset) | Configure SMTP directly instead |
Set CRAWLER_THRESHOLD near your normal peak. Far above it, the alert
never fires and is not a tripwire — run --dry-run for a few days and
pick a number a busy day would actually reach.
Modes
crawler-alert.py # daily: mail only if over threshold
crawler-alert.py --weekly # 7-day summary, always mails
crawler-alert.py --dry-run # print instead of mailing
Only --weekly fetches ranges; the daily check needs no network.
Sample output
==============================================================
LEGITIMATE CRAWLERS (source IP inside vendor's published ranges)
==============================================================
bot verified spoofed via CF IPs
ChatGPT-User 0 561 0 0
ClaudeBot 222 161 0 14
OAI-SearchBot 23 209 0 14
GPTBot 34 196 0 2
PerplexityBot 0 196 0 0
1909 requests claimed an AI-bot identity; 323 verified (16.9%).
1586 failed IP verification (spoofed). 0 arrived via Cloudflare
and cannot be verified by IP - not counted either way.
Top paths fetched by verified crawlers:
117 /robots.txt
73 /sitemap.xml
13 /explore/repos
Limitations
Cloudflare-proxied requests cannot be verified. If traffic reaches
Traefik through Cloudflare, the logged address is Cloudflare's edge and
not the client. Those hits go in a separate via CF column rather than
being guessed at. traefik-accesslog.yml shows how to recover real
client IPs with forwardedHeaders.trustedIPs.
Some vendor lists are stale. Perplexity's has 8 prefixes and was last updated in February 2025; Apple's dates to 2023. Genuine traffic from those two may fail verification. A 0% verified rate for a small vendor is weaker evidence than it looks.
No reverse-DNS verification. Amazonbot and Meta's crawlers can only be checked by rDNS or ASN, neither of which is implemented. Their traffic appears in the user-agent tally but not the verified table.
IPv6 is verified only where vendors publish v6 prefixes, which most do; addresses outside those are treated as unverified.
This is a reporting tool, not an enforcement one. It tells you what
happened. Blocking is a separate decision, and robots.txt only works
on the bots that already respect it — which, per the numbers above, are
exactly the ones not causing the load.
License
0BSD — see LICENSE. Do what you like with it.