What is a Backdoor Attack?

Some attacks slam the door right in your face and make a lot of noise. But those that keep security teams busy at night are the silent ones. They sneak in quietly, hide in the normal processes, and stay for weeks or months until someone spots them. This is the gist of a backdoor attack.

So, instead of breaking in forcibly, hackers produce or find a secret way that no one is looking for. In this way, they can always go back to the place to steal data, do lateral movements, or install new malware without raising any alarms. That’s why backdoor attacks, for the most part, are very hard to detect and, therefore, quite deadly.

What Is a Backdoor in Cyber Security?

When people ask what is a backdoor in cybersecurity, the most straightforward answer would be a concealed entry point that goes around the normal way of authentication. It’s a lot like having an extra key that no one has thought of. Backdoors are like any other product behind the facade of legitimate services and usually employ trusted credentials to seem normal.

Some of them may be developers’ tools or vendor access ports, and in the case of a few, they are created by malware. The threat becomes one when attackers discover the routes and use them as a continuous entry point for spying or as a part of a multi-stage attack without breaking into the system ​‍​‌‍​‍‌​‍​‌‍​‍‌again.

How do Backdoor Attacks Work?

Every backdoor attack involves three stages: creation, hiding, and misuse. This is the application of a backdoor mechanism.

• Backdoor Creation: Backdoors appear by means of malware infection, exploited vulnerabilities, or forgotten developer and vendor access paths. Once discovered or installed, such hidden entry points start to serve as long-term gateways for attackers.
• Hiding and Persistence: Attackers disguise the backdoors as normal processes, memory-only tasks, or system services. Some attach themselves to the startup routine, while others impersonate routine traffic. These backdoors are designed to remain unnoticed for the longest time possible.
• Control and Abuse: Attackers return through the backdoor to steal data, move laterally, deploy ransomware, or drop new malware. Persistent access lets them repeat these actions at any time.

Types of Backdoor Attacks

Although there are many kinds of backdoor attacks, each one has its own set of dangers and risks:

• Malware-Infected Backdoor Attacks: Many backdoor attacks are created as a result of malware infections. The malware produces Trojan horses, worms, or spyware, which create access tools to let attackers gain entry into a computer again. 
• Backdoor Attacks on Firmware and Hardware: These types of backdoor attacks exist under the control of the operating system. They hide in the BIOS, UEFI, routers, modems, and hardware, so antivirus software and firewalls find it hard to locate and remove.
• Application-Level Backdoor Access: In some instances, the product development team inadvertently creates a backdoor entry due to poor security practices.  This includes debug accounts, hard-coded passwords, or an API that has no security features.
• Cloud and Service Misconfiguration Backdoors: Open cloud storage, insecure IAM policies, weak default passwords, and APIs may provide attackers access without any software vulnerabilities present in the user’s system.
• Insider-Created Backdoor Attacks: In a few circumstances, an employee or contract employee may intentionally create backdoor access points for future use. As these access points are created by a trusted individual, they can be the most difficult to locate.

Common Entry Point for Backdoor Attacks

Most backdoor attacks begin with an error, misconfiguration, or misplaced trust. The following are some common backdoor entry points into an environment:

• Phishing emails: Trojans or loaders provide hidden access to the environment once users download or open a malicious file.
• Exploited Unpatched Vulnerability: Attackers use web applications, VPN appliances, or remote access tools that were never patched to create an invisible entry point into the environment.
• Credential Stuffing: Leaked or weak passwords are used as a brute force method to gain access to systems without being detected.
• Cloud Configuration: Misconfigured cloud storage (open buckets) or cloud storage accounts (overly permissive IAM rules).
• Default or Forgotten Passwords: Vendor accounts or administrator accounts that have never been removed, have default passwords, or have never updated administrator credentials.

Why Backdoor Attacks Are So Hard to Detect

The truth behind backdoor attacks is that they are designed to be invisible. Backdoor attacks are difficult to detect for several reasons:

• They do not go through authentication.
• They behave as if they were part of a normal system’s operation;
• They exist in firmware and drivers.
• They do not cause enough disruption to alert anyone.

Unlike most malware that may be noisy, backdoors don’t have any noise. Many companies only discover backdoors while performing audits, working on incident response, or just after being attacked by another organization.

How to Strengthen Backdoor Security

Backdoor security is not something that can be done with just one tool. Rather, it requires a combination of visibility, strong identity controls, improved development practices, and a workforce educated about security.

Build Visibility Across Your Environment

The first step to improving your backdoor security through visibility is to get visibility into your environment using behavioral analytics and anomaly detection. These tools enable your team to detect abnormal behavior even when the threat doesn’t have a signature to be detected by traditional techniques.

Strengthen Identity Security

The next component of backdoor security is strengthening your identity security. A lot of backdoor exploitation takes place when valid credentials are used. Enforcing MFA, following a least privilege model, rotating passwords, and removing old vendor accounts are excellent first steps to significantly reduce your vulnerability.  

Remove Vulnerable Entry Points

Initial points of entry for backdoors are associated with vulnerabilities created by unpatched systems, forgotten maintenance hooks, and neglecting to update. Internet-facing applications; thus, regularly applying updates to all internet-facing applications would effectively close the most common points of entry for backdoors.  

Secure the Application Layer

The application security component of backdoor security involves reviewing all of the code within your application consistently. Reviewing code regularly, employing secure development practices, checking for hard-coded passwords, and leftover debug paths are examples of how backdoor security can be accomplished using application security.  

Train People

Human-layer security is an additional component of securing against backdoors. Most backdoor exploitation starts with phishing. Having well-trained employees within your organization who report suspicious emails quickly can significantly reduce the number of successful phishing attempts. 

Concluding Thoughts!

Backdoor attack events might not get the press they deserve. But there is much more damage being done by a backdoor attack than what you can see, hear, or feel during the course of a large, destructive attack. Backdoor attacks provide intruders with time, control, and a lack of noise, enabling them to move slowly & methodically throughout your “secure” systems with full confidence.

But backdoors can be stopped. By utilizing better identity controls, continuous monitoring, strong development practices, and an educated employee base, organizations can close these hidden doors before the attackers get the chance to exploit them.