I'd like to block all users from inside Company X from visiting my website. However I don't work at Company X. Is there an efficient way to learn what the IP is when people inside Company X access the outside world? For instance, are there logs around the Internet that might be searchable? Note that I don't care if they access the website from their homes.

  • 1
    Blocking based on IP address is pretty much pointless. There are so many ways around it that it's basically not worth doing.
    – AlexH
    Feb 3, 2015 at 16:50
  • @darkf If the OP doesn't care if the user's access from home, then he doesn't seem to care about ways users might bypass IP blocks.
    – schroeder
    Feb 3, 2015 at 19:20
  • The thing is, I am using this to block people permanently. I can store a datum on the client system that I later detect even if they access my site from a coffee house.
    – Icann
    Feb 8, 2015 at 5:49

3 Answers 3


There are certain companies that provide such information.
An easy way is to go to the following url and put the company name you want to get the adresses for into the search box:


You will be presented with a list of ip addresses connected to the specified company if there are any.
The link leads to the "BGP Toolkit" of Hurricane Electric, a internet service provider. It the tool behind that link vanishes at one time you might find similar tools from other providers.


Most companies provide internet access through proxy server(s). If you can determine their proxy server IP addresses you can simply block their access.

Alternatively many companies have a block of IP addresses assigned to them, you might be able to determine these from whois lookups, then you can block their whole network segment.


If you know a few accesses done by such employees from their company, you can easily map the ips used to a range with a whois lookup (it may even be a single ip if they go out through a proxy).

If they have several sites they may exit from a few ranges.

  • 2
    I read that part as "It's okay for them to access from their homes" but not from work. I may be wrong though!
    – AlexH
    Feb 3, 2015 at 17:03
  • @darkf I read it the same way you did
    – schroeder
    Feb 3, 2015 at 19:21
  • @darkf you are probably right. Rereading their question, I was reading it as if it said «I don't care if they access the website from their homes ''or not''» :( I removed that part.
    – Ángel
    Feb 5, 2015 at 0:52

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