I said they can easily watch any particular file they wish to.
Most IP's are dynamically assigned from ISP's, especially those on DSL. Also carrier grade NAT destroys that entire scheme you put in, as you now have 10+ clients connecting from the same external IP.
Track by IP is the absolute worst method you could ever attempt to use.
Anyone with IT expertize knows that dynamic IP assignment is no problem to track this since you're actually LOGGED to the PlayOnline service while you're updating your game. They take YOUR current IP and the date/time you updated the game *FROM POL LOGIN HISTORY* and cross with the update server logs to check WHICH files YOUR IP downloaded. If you re-downloaded the LAMP dats out of 35 THOUSAND files the likeliness of unintended corruption of those specific files is very low IMHO.
My point is: They CAN tell people who cheat apart from people who don't if they really want to.
Edit: Oh and we have an update next week. I have no intention to help cheaters, but whatever. It is not intentional if that is the effect of this post.
This is a long secondary conversation we could get into. Suffice to say, no it doesn't work that way, and yes they could change it to work that way but then we'd know about it and it would be trivial to work around. And then it would only attempt to catch people who have yet to modify their dats in the future, it would do nothing for those who have already done so in the past.
You connect to the update server, download a new has table, check the list of files for those hash's. If they match then no download is conducted, if they don't match then their marked for download. They are not now nor will attempt take apart that file to determine what changes were made, only that it doesn't match the new updated hash. No info is transmitted to the update server btw, its the update client that does the hash comparisons and composed the file list.
Your idea would actually ban every single player on update, not just the ones who modded their dats.
Now would you like me to get you a ruler or did you bring your own?