Admin, Server, Dos, Log, Steal And Kill – The 6 Types Of Trojans

A few days ago I explained what a Trojan is but did you know that there are 5 6 distinct types of this nuisance?

Each serves a different purpose and some may have more than one of the following functions, or will facilitate the downloading of further Trojans onto your system.

I was originally going to detail 5 types of Trojan but a sixth emerged just over 24 hours ago.


Here are the various types of Trojans that you want to be avoiding –


A remote administration variety of Trojan gives the hacker behind it a great level of control over the victim’s computer.

Typically, they will be able to function without being detected and will facilitate certain functions such as modifying the registry, uploading and downloading files, running files and even initiating and intercepting various types of communication between the PC and the outside world.


The file server trojan creates a file server on the victim’s computer.

This server, which is typically configured as an FTP server, will allow the hacker to monitor network connections and to have sufficient control to be able to upload and download their own files.

Often this ability to upload files will lead to the more powerful administrator Trojan, as above, being installed,

File server Trojans are usually very small files, possibly less than 10 kilobytes in size, meaning they are easily disguised, attached to emails or discreetly connected to other files.

One of the ways in which file serving Trojans are distributed is via those funny forwarded messages you receive from your friends.

Another means of distribution is with small downloadable games, so be careful of both of those.


The DDoS Trojan is key to ensnaring computers into a botnet.

Large numbers of machines are tricked into installing the DDos (Distributed Denial of Service) Trojan and then the hacker can control one, some or all of those machines remotely via a client which communicates with a master server.

Through this primary machine in their zombie network the hackers can direct attacks at specific companies, computers or websites.

By bombarding the target server with traffic they can bring it to its knees, effectively making it unavailable to genuine users.

DDoS attacks are often directed at famous brands and those behind them may make financial demands in order to cease their activity.


Keylogging Trojans utilise spyware in order to record everything that a user types on their machine.

All their keystrokes are logged and recorded and, when the hacker makes a request, are then emailed onto them via the Trojan.

Whilst there may be many uses for the information that these Trojans grab, it will almost certainly be for the hacker’s financial benefit, either through some sort of card fraud or, worse, via identity theft.


The fifth type of Trojan is the sort that will attempt to steal your passwords.

They will use your email to communicate any passwords they discover back to the hacker.

Again, this type of information will typically be used for theft as many people will only be using passwords in association with their bank accounts or credit cards.


Just a couple of days ago a new breed of Trojan emerged.

This new threat, known as Trojan.Killfiles.904 is not designed to spy on you or steal your money.

Instead, its sole purpose appears to be the destruction of your data.

Quite what the motivations behind it are I do not know but its certainly something you want to be avoiding!

Do you have any questions about Trojans, or are there any other types that I’ve missed?

About Lee Munson

Lee's non-technical background allows him to write about internet security in a clear way that is understandable to both IT professionals and people just like you who need simple answers to your security questions.


  1. I believe I have a Remote Admin Trojan. How do I identify where it’s at and get rid of it? This thing is logging onto my internet system using my TCP/IP address, which results in my being kicked off. It prohibits my downloading antiviruses that might remove it and if it does let me download them, such as Stopzilla, I get the “blue screen of death” and the computer crashes…….HELP!!!!! Please!!!!!!

    • Have you tried using one of the many online antivirus scanners instead of downloading one Keith?

      • I have. The scanners get shut down or in some way cut off to the point that nothing is done. This thing is protecting itself past anything I have ever seen. When I do get something downloaded to deal with this, and the trojan allows it to run, when I try to do something to with it, I am told that I have to log in as admin to perform that function. My account is the only account on this computer.

  2. I’ll be with you on that very soon – I’m rummaging around my box of computer bits, looking for a 2nd hard drive so that I can run Windows 7 RC myself – have heard great things about it from you and others.

  3. David Alexander says:

    Thanks Lee,

    I am using the trial Kaspersky that comes free for 6 months with the Windows 7 RC and I am very happy with both at this stage.

    Best wishes

  4. Hi Lee,

    Great post, very useful information.

    Any advice on the best antivirus solution, both free and paid, that I could pass on to our members?

    A new perspective on protection against these threats will be very helpful.

    Best wishes


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