Hi Daniel,
 > What is the difference between a Trojan and a virus?
 A trojan is a program that has a hidden 'feature' that does something nasty 
to the computer but does not infect other programs.
A virus is something that spreads by infecting other programs (boot sectors 
etc) it may not do any damage to the system or on some trigger like the date 
do things like format the hard disk.
 > What in detail is a Trojan?
In general a stand alone program that as well as doing the documented 
function in the background do something nasty but does not spread.
Regards, Malcolm.
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