What is a Backdoor Attack?

In cybersecurity, a backdoor is a means of bypassing an organization’s existing security systems. While a company may have various security solutions in place, there may be mechanisms in place that allow a legitimate user or attacker to evade them. If an attacker can identify and access these backdoors, they can gain access to corporate systems without detection.

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How Does a Backdoor Work?

Every computer system has an official means by which users are supposed to access it. Often, this includes an authentication system where the user provides a password or other type of credential to demonstrate their identity. If the user successfully authenticates, they are granted access to the system with their permissions limited to those assigned to their particular account.

While this authentication system provides security, it can also be inconvenient for some users, both legitimate and illegitimate. A system administrator may need to gain remote access to a system that is not designed to allow it. An attacker may want to access a company’s database server despite lacking the credentials to do so. The manufacturer of a system may include a default account to simplify configuration, testing, and deployment of updates to a system.

In these cases, a backdoor may be inserted into a system. For example, a system administrator may set up a web shell on a server. When they want to access the server, they visit the appropriate site and can send commands directly to the server without needing to authenticate or configure corporate security policies to accept a secure remote access protocol like SSH.

How is a Backdoor Used by Hackers?

A backdoor provides access to a system that bypasses an organization’s normal authentication mechanisms. Cybercriminals, who theoretically lack access to legitimate accounts on an organization’s systems, can use it to remotely access corporate systems. With this remote access, they can steal sensitive data, deploy ransomware, spyware, or other malware, and take other malicious actions on the system.

Often, backdoors are used to provide an attacker with initial access to an organization’s environment. If a system administrator or other legitimate user has created a backdoor on the system, an attacker that discovers this backdoor may use it for their own purposes. Alternatively, if an attacker identifies a vulnerability that would allow them to deploy their own backdoor on a system, then they can use the backdoor to expand their access and capabilities on the system.

Types of Backdoors

Backdoors can come in various different forms. A few of the most common types include:

Trojans: Most backdoor malware is designed to slip past an organization’s defenses, providing an attacker with a foothold on a company’s systems. For this reason, they are commonly trojans, which pretend to be a benign or desirable file while containing malicious functionality, such as supporting remote access to an infected computer.
Built-in Backdoors: Device manufacturers may include backdoors in the form of default accounts, undocumented remote access systems, and similar features. While these systems are typically only intended for the use of the manufacturer, they are often designed to be impossible to disable and no backdoor remains secret forever, exposing these security holes to attackers.
Web Shells: A web shell is a web page designed to take user input and execute it within the system terminal. These backdoors are commonly installed by system and network administrators to make it easier to remotely access and manage corporate systems.
Supply Chain Exploits: Web applications and other software often incorporate third-party libraries and code. An attacker may incorporate backdoor code into a library in the hope that it will be used in corporate applications, providing backdoor access to systems running the software.

How to Prevent a Backdoor Attack

Some best practices for protecting against exploitation of backdoors include:

Changing Default Credentials: Default accounts are some of the most common types of backdoors. When setting up a new device, disable the default accounts if possible, and, if not, change the password to something other than the default setting.
Deploying Endpoint Security Solutions: Backdoors are commonly implemented as trojan malware. An endpoint security solution may detect and block known malware or identify novel threats based on unusual behavior.
Monitoring Network Traffic: Backdoors are designed to provide remote access to systems via alternative means that bypass authentication systems. Monitoring for unusual network traffic may enable the detection of these covert channels.
Scanning Web Applications: Backdoors may be deployed as web shells or integrated into third-party libraries or plugins. Regular vulnerability scanning can help to identify these backdoors in an organization’s web infrastructure.

Prevent Backdoor Attacks with Check Point

Backdoors provide attackers with unauthorized access to an organization’s systems. To learn more about this and other leading cyber threats, check out Check Point’s 2023 Cyber Security Report.

Check Point Harmony Endpoint provides threat prevention and detection for many types of malware, including backdoor malware. Learn more about Harmony Endpoint’s capabilities by signing up for a free demo today.