Which companies own which IP address blocks is public information.
> When you travel do you put the hotel you're staying in on LinkedIn?
Conferences are announced; advertised, even.
> Also, not everyone is on LinkedIn in the first place.
That's OK, companies do a fine job publishing employee information all on their own.
> You asked 'What can be done with this information?' - this is the list of things you can do with that information.
You've moved from Step A, getting the information to Step B, correlating the information, but you've left off Step C, which is profiting from the information. What is a benefit you can gain from knowing someone at some IP address opened your email? Can you get that benefit some other way, such as by looking in a phone book or viewing the company's website?
People are working from home! That's the entire context of this thread! They aren't using corporate IP addresses! And they don't do it when travelling either!
> Conferences are announced; advertised, even.
People travel for other things beside conferences. For example to a meeting or client site.
> That's OK, companies do a fine job publishing employee information all on their own.
Many don't do this.
> What is a benefit you can gain from knowing someone at some IP address opened your email?
I've already listed all these things.
> Can you get that benefit some other way, such as by looking in a phone book or viewing the company's website?
Yes, people not listed in a phone book or the company website.
You're listing exceptions, but they don't apply to everyone. If they don't apply to everyone then you can catch some people.
Try this to help yourself understand - people do in fact use tracking images. Therefore, do you think that maybe there's a benefit to doing this? Otherwise why do you think they do it?
Do you put your IP number on LinkedIn?
When you travel do you put the hotel you're staying in on LinkedIn?
Also, not everyone is on LinkedIn in the first place.
> It would be arbitrary to have the image links switched out by the server so they always go through a proxy/urldefense and it would never be the user ip address or user agent the attacker sees.
The word 'arbitrary' doesn't make any sense to me in this context so not sure what you mean sorry.
In general, I don't know what you're trying to say - that there are ways to try to defend against these attacks? Yeah I know. I'm not sure what point of mine you're refuting or replying to anymore.
You asked 'What can be done with this information?' - this is the list of things you can do with that information. Can you defend against some of it? Yes to some extent. But it still leaks for many people.