What is Backdoor?
March 16, 2023
A backdoor is any method that allows someone to access your device without your permission or knowledge remotely. Stakeholders can install a backdoor on your device using malware, vulnerabilities in your software, or even directly installing a backdoor in your device's hardware/microware. These interested parties could be hackers, government officials, IT professionals, etc. As they infiltrate your machine without your knowledge, they can use backdoors for various reasons, such as surveillance, sabotage, data theft, cryptojacking, or malware attack.
Backdoor Trojan Detection Challenges
Since a backdoor can be inactive for a long time, the victim may not even be aware of its presence. Even if a backdoor is detected, the victim cannot determine who implemented it or what information has been stolen. Suppose a backdoor is found in a legitimate program. In that case, the developer can hide his intentions by passing it off as an accidental bug. Although backdoors have much in common with remote administration tools and Trojans, they are much more dangerous and complex. Although they all work on a similar principle, backdoors have been relegated to a separate category.
So why are some of them detected by antivirus products as Trojans, while others are not? The answer is simple: the determining factor is not functionality but the order of installation and visibility in the system. For example, the installation of a full-fledged remote administration utility is accompanied by numerous license agreement dialogs and a graphical reflection of the process. Backdoor, on the contrary, does it silently and unobtrusively. After launching the installation file, no messages appear on the screen indicating it is being installed.
While running, Backdoor does not show its presence in any way. You can find it neither in the taskbar nor the system tray and, quite often, even in the list of active processes. As for the honest "administrators", they always signal in some way about their work. Usually, it is an icon in the system tray or the taskbar. You can almost always see them in the list of active processes or among services. Finally, any full product has an uninstall function, present in the list of installed applications, which the user can use at any time. The Backdoor can only be removed with special software or "surgically".
Examples of Backdoor Trojan Attacks in 2023:
- Mirai variant "Pandora" infects Android TV for DDoS attacks.
- Gozi and IcedID Trojans Spread via Malvertising
- FIN8 Updated Sardonic Backdoor to Deliver Noberus Ransomware
- Trojanized TeamViewer Installer Spreads njRAT
- TeamTNT Group Returns with Silent Bob Campaign
- Shuckworm Gang Attacks Ukrainian Companies Using Pterodo Backdoor and USB Drives
- Domino Backdoor is Lead by FIN7 and Conti Actors
- Vulnerability Found in Twitter Code That Provokes a "Shadowban" of the Victim
Classification of Backdoors
Backdoors can be installed in two parts of your system - software and hardware. Now we will look at each option in more detail:
1. Hardware/Firmware
Physical modifications that can provide remote access to your device. Hardware manufacturers can introduce hardware-type malicious objects (also known as hardware implants) at one of the production stages. Such backdoors cannot be removed by replacing or updating software and are not detected by code scans or anti-virus software.
2. Software
These are usually malicious files that carefully hide their traces so that your operating system does not know someone else has access to your device. As well as hardware backdoors, software backdoors can get into the design from the manufacturer (known as software implants). However, more often, it happens with direct user involvement.
Backdoors also differ in the methods of implementation, among which we can distinguish:
1. Hardware Backdoors
Hardware backdoors include modified computer chips or other firmware/hardware that allow uncontrolled access to a device. These can consist of phones, IoT devices such as thermostats, home security systems, and routers and computers. These backdoors can transmit user data, provide remote access, or be used for surveillance. Hardware backdoors can be shipped with products (either illegally by the manufacturer or for some nefarious purpose) or installed physically in case the device is stolen.
2. Cryptographic Backdoors
A cryptographic backdoor is essentially a "master key" that can unlock every piece of encrypted data that uses a particular encryption protocol. Because encryption standards such as AES use end-to-end encryption, only parties that have exchanged a randomly generated cryptographic key can decrypt the transmitted information. By manipulating the complex mathematics of a particular cryptographic protocol, backdoors can give an external user access to the encrypted data between the parties.
3. Backdoor Trojans
Trojans are malicious files that impersonate legitimate files to gain access to your device. After obtaining the necessary permissions, the Trojan can install itself on your device. In addition, trojan backdoors can allow attackers to access your files or install more severe malware on your device.
Rootkits
Rootkits are more advanced malicious programs capable of hiding their activities from the operating system, with the operating system granting them security privileges (root access). Rootkits can allow attackers to remotely access your device, modify files, monitor your activity, and harm your system. Rootkits can take the form of both software and physically changed computer chips.
Once in the system, backdoors give the attacker the needed data and allow him to control the machine. This can happen in three ways:
- BindShell - the malware waits for an external connection;
- Back Connect - the backdoor connects to the cybercriminal's computer itself;
- Middle Connect - data is exchanged between the cybercriminal and his tool using an additional server.
What Are The Backdoor's Goals
The target audience of backdoors is no different from other malware. Attackers are usually interested in devices belonging to commercial organizations, government agencies, enterprises, etc. However, ordinary users' computers are also of concern to them. Being challenging to detect, backdoors can be present on a system for a long time (months or even years), allowing the victim to be monitored, have their data stolen, and have their device used for other nefarious activities by hackers.
After gaining access to the system, the hacker can thoroughly learn the user's identity and use this information for criminal purposes. Thus, computers can be stolen from secret documents, developments or documentation, and trade secrets, which can be used by company competitors or sold in the appropriate places. One of the backdoor's unpleasant features is that it is as dangerous as the payload it can put on a device. Regardless of its task, after all, the cybercriminal may delete all the files on the victim's machine or completely format the hard drives.
Sources of Threat
A backdoor in a system can appear either with legitimate software (including OS) or with an unintentional vulnerability. Also, individuals with physical access to a computer can install a backdoor on the victim's computer. Sometimes developers intentionally leave backdoors in software and hardware for remote technical support. But in most cases, backdoors are installed either by cybercriminals or intrusive governments to gain access to the victim's device.
In some cases, an inattentive PC user may unknowingly install a backdoor from a file attached to an email or along with downloaded files from a file-sharing service. Fraudsters disguise the infection with suggestive names and texts that induce the victim to open or run the infected object. In addition, software backdoors can be installed in a computer by other malware, just as unnoticed by the device owner. Like worms, these malicious programs secretly spread through the information system without displaying any warnings or dialog boxes that might make the user suspicious.
How to Prevent Backdoor Attacks?
Unfortunately, no one is immune to backdoor attacks. Hackers are constantly improving techniques and creating more sophisticated malicious files to gain access to user devices. However, by following the instructions below, you can reduce the risk of a successful backdoor infection:
Close unused network ports.
An open port on your network can receive traffic from remote locations, resulting in a weak point. Hackers usually target unused ports, allowing them to install backdoors that gain access to your device. No software will alert you to the intrusion. However, this isn't a problem for most home users since home router ports are closed by default. However, small business owners should exercise caution when opening ports.
Use strong passwords.
An insecure or default password is a green light for hackers to access your accounts. Once they crack one account, they can easily access your other accounts and devices. This is how hackers used the Mirai botnet in 2016, which affected 2.5 million IoT devices worldwide. It was designed to scan the Internet for IoT devices with unchanged default passwords, then hack into those devices and enslave them with a botnet. We recommend using a only strong passwords and using MFA. It will protect your accounts from unauthorized access.
Keep your software up-to-date.
Hackers can use exploits to install malware on users' devices. Installing updates for your operating system may cause some discomfort. However, in this way, developers fix vulnerabilities in the system, thereby reducing the risk of backdoors appearing on the system.
Download files with caution.
The user causes most malware attacks. If you get a free program that costs money or downloads the latest Marvel movie via torrent and then suddenly installs a malicious file, your system becomes vulnerable. When downloading any file from the Internet, check to see if you're only getting the file you need or if you're also getting the malware as a bonus. Even if the file behaves like the file you are looking for, it could be a trojan. Always download files from official websites, and avoid pirate sites.
Use a firewall and antivirus.
Always use advanced antivirus software as well as a firewall. This can detect and prevent malware, including trojans, cryptojackers, spyware, and rootkits. A firewall is essential for backdoor protection because it monitors your device's incoming and outgoing traffic. If someone outside your network tries to access your device, the firewall will block them. Antivirus can detect backdoor viruses and neutralize them before they can infect your computer.