IT Center Blog

Backdoors: Access Through an Alternative Access Point

January 17th, 2022 | by
A door that is open a crack.

Unnoticed access through the backdoor can be particularly tricky. (Source:

In life, sometimes it can be very useful to have a plan B or to keep a backdoor open. But would you leave your house and hide the keys to the backdoor under the doormat? For burglars, this setup would probably be an easy target. In IT as well, so-called backdoors are a very popular target for hackers. However, these backdoors are much more tricky and discreet than an open door or hidden keys under a doormat. Because even when the original breach of security, such as an open window, no longer exists, cybercriminals can still get in and out as they please via the implemented backdoor.

What is a backdoor?

A backdoor is an alternative access point to a device or software. This backdoor makes it possible to gain access to protected areas and functions of a software or even access to an entire computer system without access restrictions. Ideally, the victim does not even realize that their system has been attacked. The backdoor will then remain open, and the attacker can monitor the system at his convenience, steal data or install more malware.

Backdoors can actually be helpful in some cases. They are often legitimately implemented by developers as maintenance access points. These backdoors then provide developers with simplified access and can make it easier to fix software problems. In this case, these accesses are both documented and secured. However, most backdoors are set up by cybercriminals to gain unlawful access to a device, network, or software. Regardless of whether it was intentionally implemented by developers or introduced during a cyberattack, a backdoor always presents some security risk.

Backdoors and Trojans

Trojan horses, or Trojans in short, are programs or scripts that disguise themselves as useful applications. In the background, however, they perform a different function. The Trojan hides behind seemingly harmless applications, can extend user rights, for example, and thus creates security gaps. Backdoor programs can then be infiltrated through these security gaps. These programs then create unnoticed access to the system. In this case, the Trojan merely serves as a supporting tool to create a backdoor in the background.

This combined use of Trojans and backdoor programs can be particularly treacherous. If the Trojan is detected during a virus scan, it can be removed. However, the actual security hole that has been created is often overlooked and the backdoor remains open. Depending on the type and complexity of the backdoors, they can be very difficult to find.

How can I protect myself from backdoors?

Anyone who spends a lot of time on the Internet also exposes themselves to high risks. As with other cyberattacks, there is never 100% security. Since some backdoors are created with the help of Trojans, the use of an adequate antivirus program is essential and can already be a first hurdle for cybercriminals. However, blind trust in antivirus programs and firewalls is unfortunately not enough, as malware is becoming ever better camouflaged and cyberattacks ever more perfidious. Users should therefore always remain critical, especially when clicking on links, visiting unknown websites, downloading new software, or opening attachments in e-mails. Ideally, macros should always be deactivated when opening unknown files, for example.

Outdated versions of systems and applications also represent a high security risk. So always make sure to install new updates and patches as soon as possible. The use of so-called open-source programs can also reduce risks, as the source code of the program can be openly viewed at any time and is easier to check for secret backdoors.


More examples and tips on the responsible use of your devices and software can be found in the IT Center blog under the tag IT security. More information about malware and backdoors can also be found on the website of the German Federal Office for Information Security (german only).


Responsible for the content of this article is Stéphanie Bauens.

2 responses to “Backdoors: Access Through an Alternative Access Point”

  1. Günther says:

    OK danke für die Erklärung, ich benutze Avast und habe eine Meldung bekommen das ein Backdoor gefunden wurde bei einer US Staatseinrichtung und wusste nicht was das bedeutet für mich. Jetzt verstehe ich, sollte also mit Schutzprogramm alles gut sein.

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