All that you have an old installation, do the following and master server will work.
All that you have a new installation it all works in the 1st place
-open infiltration.ini
-Replace the master server addresses
[Engine.GameEngine]
ServerActors=INF_Browser.INF_BrowserUdpServerQuery
ServerActors=IpServer.UdpServerUplink MasterServerAddress=unreal.epicgames.com MasterServerPort=27900
ServerActors=IpServer.UdpServerUplink MasterServerAddress=master0.gamespy.com MasterServerPort=27900
ServerActors=IpServer.UdpServerUplink MasterServerAddress=84.255.245.128 MasterServerPort=27900
ServerActors=IpServer.UdpServerUplink MasterServerAddress=infmaster2.sobservers.com MasterServerPort=27900
[INF_Browser_All_UT]
ListFactories[0]=INF_Browser.INF_BrowserGSpyFact,MasterServerAddress=84.255.245.128,MasterServerTCPPort=28900,Region=3,GameName=ut