host.dat definition, relationships, removal:

The host.dat file is an essential part of a particular parasite and therefore is responsible for the pest's malicious activity. Exact purposes of host.dat depend on the related parasite's type and carried payload. Some threats can use host.dat to serve annoying pop-up advertisements or store certain configuration settings, while others need it to corrupt files, steal user confidential information or run a spreading routine. In any case, DO NOT open this file!
The host.dat file is installed and used by NaviHelper.
Please note that the host.dat file actually may be a fully legitimate part of the operating system or legitimate software. Often parasites use files with unsuspicious names, but malicious functionality. You should always carefully check the file before deleting it. It may not be related with malware, but can be required by your essential programs to work properly.