Trojan software has nothing to do with condoms, except perhaps that the parents of the Trojan sender should have used a condom. Trojans are named after the Trojan horse of legend, used by the Greeks to end the siege of Troy.
The trojan horse was seen as something valuable and welcome to the Trojan people and they accepted it in, past their defenses, but it was really just a vessel for the enemy who crept out when the Trojans were not watchful.
A Trojan in internet terms will likely appear to be a desireable piece of software. One was hidden in a South Park screensaver for instance. Inside the useful software is the enemy code. It is usually a hidden server opening up remote access to your computer. Anyone can then connect to the trojan's server and do anything they want with your system. They can view and download your files. They can delete whole directories. They can set a password on your screensaver locking you out of your own system.
This isnt hacking, since its just a user with a malicious program. If you don't accept and run the trojan it can't harm you and the attacker can't gain access.
The common advice about trojans is not to accept any file at all from people you don't trust implicitly. I don't fully go along with that. I say dont accept executable files from anyone you don't trust to have fully checked and swept all their own files for viruses and trojans.
The point of trojans is that they are hidden. If the application the trojan is hidden inside is good then people who don't know theres a trojan in it may well share the software with their friends, thus unwittingly affecting people who trust them. Its not whether you trust the sender, its whether you trust the software itself as well.
However, in practice, everyone can be persuaded to accept an unsafe file if the right pitch is made by the right person. Remember that when tempted to accept anything from anyone and be sure you have backed up your system and have good anti-trojan and anti-virus software.
I mentioned Puppet in the page on Nukes. he is the author of the much-acclaimed NukeNabber and has also created a great anti-trojan program called The Cleaner. If you are ever going to accept a file from anyone, including e-mail attachments then get The Cleaner now!
For anti-virus protection you really should have installed that before even getting an ISP. The net is full of old viruses, hidden in everything from html enabled e-mail to Word documents. Most viruses are passed on unwittingly, not by enemies, but by trusted friends. Try Norton Anti-virus or similar.
Beyond.com offer a wide range of bargains on software of all kinds. You should ensure that you have anti-virus software, good backup software, and whatever bug detection software you feel able to use.
Protect yourself ... its not anyone else's responsibility and its all too common to hear people who thought it didnt apply to them. If you dont have the latest anti-virus protection then this does apply to YOU
IRChelp.org - Trojan Page has all the basic information plus a good set of links to fix some of the specific trojans known to be in circulation.
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