What bot is generating this user-agent?

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.1

There was no Firefox version 40.1

From website logs (a) it only ever requests the homepage (b) it never requests robots.txt (c) it originates from all over the world, frequently from ISP hostnames, in thousands of pageviews.


This user agent string is used by a brute force that tries to login as an administrator to a Wordpress site. For me the bot tried about 3000 times within about 18 hours with no success.

  • I am just noticing the same agent, by accident with lots of requests which cause some PHP notice in my logs. Of course the user agent is not a reliable user identification, but the fact that it requests tons of pages makes the identification more reliable.
    – Anse
    Jul 18 '17 at 15:15

User agent titles can be "spoofed", there's no guarantee that:

  • It's the same bot
  • It is in fact a bot

There are several references to the same user agent on the internet. For instance this github account has a large list of agents, and the one you have is listed there:


It is also listed in a JSON like format on pastebin:



Clever sys admins only accept requests from legit browsers to prevent bots. So bots pretend to be well kwnown browsers. The user agent is no more than a HTTP header and can be forged by any HTTP library in any language. Do you want a request from MS/DOS 2.11 or even the good old Sinclair ZX81 using lynx? I can send it at once...

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