[Myth] No open port = no Trojan

Last update on August 3, 2009 04:36 PM by fahd_zboot
Published by jak58

No open port means No trojan




Myth


Leaving no ports open on my PC , I'm sure I will not have any Trojan on my computer.

Reality


FALSE.

Explanations


An open port is not necessary to control a computer on which there is a Trojan horse installed.
  • Some Trojans are on IRC channels to seek instructions. So: No open port, it is the Trojan itself that initiates the connection to Internet.
  • The Trojan horse may very well open the ports at certain hours.
  • There are techniques that allow you to open ports without visible scanners port (Port Knocking, Single Packet Authorization, etc..)


It is therefore wrong to assume that you do not necessarily Trojan if you have any ports open.
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