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Danger level 1
Type: Trojans
Common infection symptoms:
  • Blocks internet connection
  • Cant change my homepage
  • Connects to the internet without permission
  • Installs itself without permissions
  • Slow Computer
  • Slow internet connection
  • Strange toolbar installed without Your permission
  • System crashes


Trojan.Koutodoor is a group of Trojans that consists of malware dropper components, backdoors and a whole list of Trojan variants that install unwanted programs onto your computer. For example, TrojanDropper:Win32/Koutodoor.B is a dropper Trojan that installs other components of Trojan.Koutodoor on the target computer. The user can get infected with this Trojans when he lands on a website that looks like an image file. For example, the end of the website's URL might be .jpg which would normally indicate an image file, but in this case, once the user opens the file, Trojan.Koutodoor is activate and installs the payload, that includes such malware as Trojan:WinNT/Koutodoor.C.

Even though there are no common infections symptoms you might notice additional shortcuts added to the Quick Launch toolbar, and there might also be another favorite on your Web browser leading to a website

Not only does Trojan.Koutodoor make you access websites that contain other malware, it can connect to a remote server itself. For example, Trojan:Win32/Koutodoor.E connects to in order to let the hacker behind this infection know that yet another computer has been infected.

Another version of Trojan.Koutodoor that is called Trojan:Win32/Koutodoor.F terminate IEXPLORE.EXE and then can perform a list of actions on the computer, based on what the attacker wants it to do. It even locks the Internet Explorer toolbar, and does not allow the user to access the websites he wants. Then it connects a remote host at via port 80. Then Trojan.Koutodoor downloads other malware and installs them on the computer, and uploads data it has gathered from the target computer.

In short, Trojan.Koutodoor is a dangerous group of Trojans that trespasses into your system and performs a whole list of evil deeds. Deleting it manually might be a bit tricky, because it is a multi-component threat, however, if you get yourself a computer security program you will be able to remove Trojan.Koutodoor automatically and your system will be protected from similar Trojan attacks.

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