A Trojan is a Remote Admin Tool , this a server that runs invisible on the victim and the client that you run on your computer to take control of the victim ,you cant connect to the victim if he hasnt run the file yet ,there are many trojans around with different commands , layouts , extras ect , the trojans usually include a server builder that its safe to run on your computer you can browse to the server.exe and edit some options , like passwords or ports before sendin it...
How it works
When the victim runs the server.exe the server runs invisible on the victim ,he doesnt see anything.The server keeps a port open lets say 27374 port and waits for a connection , some servers of some trojans may have passwords in that case the server is stand by for a connection and a password , when you log into the victim the server enables you to run many commands by pressing buttons in your client ,the trojans were made to run those commands faster by pressing buttons.
All the antiviruses like Mc Affee ,Norton etc will identify a virus and try to delete all the trojan servers you plan to send to your victims , also all the trojan clients even the server editor are identified like viruses with all their files so dont spam saying that such files are infected, they are not, they are original viruses.
What to do with a trojan
You can play with it, open the cds and laugh like stupid that you are, or redirect ports for other purposes,enable keyloggers and get the passwords, log on into their mails,, you might key-log something.you can make them log in irc servers like bots to see whos online and a lot more.