How to secure your network from Trojans

A Trojan, sometimes referred to as a Trojan horse, is non-self-replicating malware that appears to perform a desirable function for the user but instead facilitates unauthorized access to the user's computer system. 

Is trojan virus Dangerous?

The short answer is yes, and the long answer is sometimes No, because there are near a thousand different trojan horse viruses and they all will most likely alter your computer in some way or another. 

Working of Trojans!

Types of Trojans:

 

1.Remote Access Trojans

2.Password Sending Trojans

3.Keyloggers

4.Destructive Trojans

5.Denial of Service (DoS) Attack Trojans

6.Proxy/Wingate Trojans

7.FTP Trojans

8.Software Detection Killers

 
How to Get Rid of Trojans:
Here are some practical tips to avoid getting infected (again). For more general security information, please see our main security help page.

1. NEVER download blindly from people or sites which you aren't 100% sure about. In other words, as the old saying goes, don't accept candy from strangers. If you do a lot of file downloading, it's often just a matter of time before you fall victim to a trojan.
2. Even if the file comes from a friend, you still must be sure what the file is before opening it, because many trojans will automatically try to spread themselves to friends in an email address book or on an IRC channel. There is seldom reason for a friend to send you a file that you didn't ask for. When in doubt, ask them first, and scan the attachment with a fully updated anti-virus program.
3. Beware of hidden file extensions! Windows by default hides the last extension of a file, so that innocuous-looking "susie.jpg" might really be "susie.jpg.exe" - an executable trojan! To reduce the chances of being tricked, unhide those pesky extensions.
4. NEVER use features in your programs that automatically get or preview files. Those features may seem convenient, but they let anybody send you anything which is extremely reckless. For example, never turn on "auto DCC get" in mIRC, instead ALWAYS screen every single file you get manually. Likewise, disable the preview mode in Outlook and other email programs.
5. Never blindly type commands that others tell you to type, or go to web addresses mentioned by strangers, or run pre-fabricated programs or scripts (not even popular ones). If you do so, you are potentially trusting a stranger with control over your computer, which can lead to trojan infection or other serious harm.
6. Don't be lulled into a false sense of security just because you run anti-virus programs. Those do not protect perfectly against many viruses and trojans, even when fully up to date. Anti-virus programs should not be your front line of security, but instead they serve as a backup in case something sneaks onto your computer.
7. Finally, don't download an executable program just to "check it out" - if it's a trojan, the first time you run it, you're already infected!

Read more: http://rafayhackingarticles.blogspot.com/2010/05/how-to-secure-your-network-from-trojans.html#ixzz0y64vzG30