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What is a Backdoor?


Cybercriminals use various methods to penetrate a device or network by exploiting the vulnerabilities in the operating system or applications. When a website is compromised, the attackers often leave some piece of malware behind to gain access back to the site. By rejecting an open door, hackers attempt to remain in control of a website and infect it continuously. This is called backdoor malware.

Backdoors in cybersecurity are the type of malware that attempts to infiltrate a system or network by exploiting a software vulnerability and providing persistence to the attackers. Attackers can breach the security protocols and gain administrative access to the system by using backdoors. Similar to a real-life robbery in which burglars exploit loopholes in a building to gain entry via a “back door.” After gaining high-level administrative privileges, the cyber attackers could perform horrific tasks such as injecting spyware, gaining remote access, hacking the device, stealing sensitive information, encrypting the system using ransomware, etc. Backdoors were initially designed to assist software developers and testers; however, the use of backdoors changed its course and caused damage to the cyber industry.

Backdoors are malicious programs that secretly allow attackers to access a system with privileged privileges. As a result, attackers can steal information, install other malware, and carry out further attacks. Even the most minor security-conscious individual should be concerned, but there is nothing to worry about. Even the trickiest of backdoors can be prevented if conventional, common-sense information security measures are followed.

Everyone is vulnerable to backdoor attacks, and hackers constantly invent new methods and backdoor malware files to get inside the target device. Hackers who gain access to your machine without your knowledge can use backdoors for a variety of purposes, including:

  • Cryptojacking
  • Data theft
  • Malware attack
  • Sabotage
  • Surveillance

How Backdoor Works?

Backdoors provide hidden entry points that allow unauthorized users unrestricted access to critical resources, and these are sneaky minor bugs that are well hidden on your network. There are two types of backdoors that can be installed in a system:

  • Hardware: A physical modification to your device that allows remote access.
  • Software: Invisible malware hides its tracks, so your operating system does not know another user is accessing your device.

Typically, backdoors are installed by either cybercriminals or intrusive governments to help them gain access to a device, a network, or a software application. Software vendors and hardware manufacturers can install backdoors in their products for remote technical support functions, but in most cases, backdoors are installed by cybercriminals or intrusive governments. A classic example is an online file converter, or P2P, that makes you believe you are downloading that great song you recently discovered when you had downloaded a backdoor.

Malware such as rootkits, Trojans, spyware, cryptojackers, keyloggers, worms, and even ransomware that provides hackers access to your device is considered a backdoor.

Types of Backdoors

  • Big and complex Backdoors: Due to their size, these are the easiest to spot. The following is an example of a big, complex, easy-to-find “Filesman” backdoor:
  • Short and simple backdoors: Backdoors can also be short and simple, and they can be used for various purposes. Following is an example of a backdoor that can be used to execute any code from a “PHP” request:
  • CMS specific backdoors: A content management system (CMS) may contain backdoors specific to it. The following example illustrates a WordPress backdoor exploit. In this case, the malicious content is hidden in the wp-options tables in the database.

Symptoms of Backdoor

  • The intruder can create, delete, rename, copy, or edit any file. It can also execute various commands, change system settings, alter the Windows registry, run, control, terminate applications, and install other software and parasites.
  • Allows the attacker to gain control of computer hardware devices, change-related settings, shut down, or restart a computer.
  • Steals confidential information, valuable documents, passwords, login credentials, identity information, logs user activity, and tracks web browsing habits.
  • Captures screenshots and records keystrokes. Additionally, it sends all gathered data to a predefined e-mail address, uploads it to a predetermined FTP server, or transfers it to a remote host through a background Internet connection.
  • Erases files, corrupts installed applications, and damages the entire system.
  • Distributes infected files to remote computers with specific security vulnerabilities and performs attacks on hacker-defined remote hosts.
  • Installs a remote FTP server capable of being exploited by malicious actors for various illicit purposes.
  • Impacts the performance of the system and the Internet connection.
  • It prevents removal by hiding its files and providing no uninstall function.

Examples of Backdoor?

  • Back Orifice: Back in Windows 98 days, Back Orifice was a backdoor that allowed hackers to control Windows systems remotely. The attacker took advantage of security flaws within Microsoft Office and cleverly disguised itself with a name that was a play on Microsoft Back Office Server, which fooled victims into thinking it was a legitimate security service.
  • KeyBoy: KeyBoy is a backdoor embedded in malicious Microsoft Word documents. In addition to simply allowing backdoor access to systems that downloaded these malicious documents, KeyBoy automatically loads the malicious DLL file after the document has been downloaded.
  • Backdoor Rootkits: Sometimes, rootkits can be used as backdoors by hackers. Rootkits are advanced malware threats that make their activities invisible to the operating system, enabling them to grant root access to the rootkits. A rootkit is a program that allows a hacker to remotely access your device, alter your files, observe your activity, and sabotage your system.
  • Emotet: Eventually, this worm-like Trojan developed into a full-service backdoor and delivery vehicle for other types of malware. EmoTet is an example of a tool that provides a wide range of functionality built with a backdoor capability. There are times when the backdoor capability is part and parcel of an attack tool instead of a standalone, dedicated backdoor.
  • PoisonTap: PoisonTap is a malicious backdoor that allows hackers access to almost any website (including protected ones with two-factor authentication). PoisonTap is a scary piece of malware, but fortunately, the only way to install it is with a Raspberry Pi connected directly to the victim’s computer.

How to Remove Backdoors?

Backdoor attacks are difficult to track since they are carried out discreetly, so it is best to prevent them from happening on your device. Backdoors can pose a severe threat to a computer system and must be removed. Backdoors are challenging to detect or remove manually. It is highly recommended to use the automatic removal option. Many security applications are available to eliminate backdoors, although some viruses may require scanning with a few different anti-malware applications. The following measures are recommended.

  • Choose plug-ins and applications carefully.
  • Keep Firewall ON
  • Keep Windows updates current
  • Monitor Apps and Extensions Installation
  • Monitor network activity
  • Stay on Top of Security Updates/Patches
  • Use a Password Manager and change passwords regularly with some degree of complexity.
  • Use an Antivirus
  • Use advanced EDR solutions like ThreatResponder to detect and delete the persistent backdoors.

How to Detect Backdoors?

Cyber security threats and ransomware attacks are increasing at a tremendous pace. It is extremely difficult for cyber security analysts and incident responders to investigate and detect cyber security threats using conventional tools and techniques. NetSecurity’s ThreatResponder, with its diverse capabilities, can help your team detect the most advanced cyber threats, including APTs, trojans, backdoors, virus, worms, rootkits, zero-day attacks, and ransomware attacks. It can also help automate incident response actions across millions of endpoints, making it easy, fast, and hassle-free.

Want to try our ThreatResponder, cutting-edge Endpoint Detection & Response (EDR), and ThreatResponder FORENSICS, the Swiss knife for forensic investigators in action? Click on the below button to request a free demo of our NetSecurity’s ThreatResponder platform.


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