The Generic Host Process could be used for DNS transferring..
It should be allowed because it is used as a transport for DNS queries..
Ussually blocking it would stop you from even going to websites.
If your concerned about a trojan / virus, I have several reccomendations:
AVG Free - A free version of the wonderful anti-virus scanner, AVG. It can be found at http://free.avg.com
NOD32 - A retail virus scanner that costs $40, but has many advantages such as proactiv scanning, and the use of little resources. I use it and I'm very happy. It can be found at http://nod32.com
and has a trial at http://www.eset.com/download/trial.htm
Housecall Scanner - A free virus scan that goes right through your browser using a Java kernel.
Any of the three should pick up any trojans and put you at rest.