Or, if you are blocked from downloading .msi files then try this zipped version:
KFSensor Professional Free Trial Version (.ZIP file)
WinPcap 4.1.3 Setup File
KFSensor makes use of WinPcap, the industry standard network packet capture library.
This enables KFSensor to work along side a host of other security tools that also make use of this library such as Wireshark. KFSensor will work without WinPcap being installed but several of its features will be disabled.
WinPcap can be installed either before or after installing KFSensor.