I logged in to a forum on two separate instances with a different ID each
time. Someone actually was able to find out that this was me logging in with
different IDs. My question is, how can any forum participant know my IP? I know
that the forum logs the IPs, but am surprised that a member was able to
identify my IP. My IP is not visible on the forum.
There’s a lot that’s not specified here, so I’ll have to make a few
assumptions. My first assumption, of course, is that you had a good intentions
using different IDs on the same forum, and that you you’re not trying to
deceive someone. (See my rant on
ethics if you wonder why I care.)
Depending on things, I can hypothesize several different ways to tell it’s
you, and not all involve IP addresses.
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You didn’t indicate which forum, or more importantly, which forum software
is in use. It’s quite possible that the forum software may not display your IP
address, but could still embed it in the HTML. A “view, Source” of the a forum
page will tell you that quick enough.
The forum software might make the IP address information to forum
administrators. So you, as a “normal” user might not see it, but an
administrator of the forum quite well could.
It might not be your IP that they’re tracking, either.
you only have to login once, and not each time you view a new page. If you
visited the forum from the same machine in both cases, it’s possible that the
cookie, or information it contains, is trackable. Again, either by a forum
administrator, or hidden in the HTML of a forum post.
The forum might include information that could be tracked to the same
machine or IP in your user profile.
Finally … and many people don’t get this at all … it could be something
as simple as your writing style. We each have our own style – including common
errors and grammatical nuances – that is fairly consistent when we write. A
sharp observer could possibly be looking at posts you’ve made under both ID’s
and noticed that they’re written in nearly identical style.
I’ve actually experienced this one at least one mailing list where a member
who supposedly left clearly returned by writing using her husband’s
membership. Her style was quite obvious, and distinct from her husband’s.
So as you can imagine, there are many possibilities.
The best solution, of course, is not to need to play these games in the
first place. But I know that there are sometimes appropriate and valid reasons.
I’ve even done it myself.