So i recently found out a easy way to fix the matchmaking in MW3, just use the old iw5mp.exe (Vers 1.9.461) provided down below and replace it with the corrent iw5mp.exe.
Matchmaking should be fixed now, but keep in mind you can only play with people having the same version as you (Vers 1.9.461)
After some additional testing it seems that all old cheats are working perfectly fine with it. If enough people use it we might be able to revive the game a bit.
Virus Scans
https://www.virustotal.com/gui/file/...2f2ac142d054de
https://virusscan.jotti.org/en-US/fi...job/vx37rqf5gn
As Always, Kind Regards