In the 1995 Sandra Bullock movie The Net, a supposedly secure and safe security program is actually a Trojan horse of sorts, allowing hackers “backdoor access” into business mainframes. It might have sounded high-tech at the time, but backdoor attacks are anything but new….

They were originally developed in the 1960s as troubleshooting tools, but transformed into malicious methods of unauthorised access by the 1980s. As the cybersecurity landscape has rapidly evolved since then, they’ve constantly faced this particularly insidious threat: backdoors.

Basically, they’re already existing clandestine entry points that allow hackers to gain unauthorised access to systems by bypassing standard authentication procedures. In fact, they can even potentially remain undetected for months as they exfiltrate sensitive data. As research firm Sansec reported in May 2025, a 6-year-old dormant backdoor that was activated recently has put hundreds of ecommerce sites at risk. Let’s deep dive into the world of backdoor attacks, their serious repercussions, and how to keep them at bay.

What Are Backdoor Attacks?

Backdoor attacks happen when threat actors employ backdoors to gain remote access into systems. These hacks allow them to gain control of system resources, install different kinds of malware or ransomware, and perform illegal network reconnaissance to extract sensitive data. Sometimes, hackers even design viruses or worms that take advantage of existing backdoors or previous attacks.

Imagine a bank vault that’s been protected with multiple layers of security, like biometric access controls, high-tech locking mechanisms, and armed guards at the front door, making it impossible to access without proper authorisation. However, if there was a large ventilation shaft that makes the vault vulnerable, then that is what you call a backdoor. They basically sidestep standard entry points to gain unauthorised access to systems.

How Do Backdoor Attacks Take Place?

Backdoor attacks usually start out by hackers scouring for weaknesses in the hardware, software, and network configuration issues. Systems that haven’t been updated or riddled with unpatched software become ideal targets as hackers plant the backdoors.

Initial access usually take place via malicious downloads or phishing attacks, such as phishing emails containing malicious attachments or links. Trojans or malware mislabelled as coming from legitimate sources are also part of these phishing schemes to gain backdoor entry into systems. Yet another way hackers gain access into systems is by exploiting vulnerabilities in various software or connected network devices, such as firewalls and routers.

Network-based backdoors allow them to reach a wider range of systems, letting them manipulate data flows across enterprises. If that wasn’t enough, attackers are even using social engineering as phishing tactics, using fake websites masquerading as something else or via fake identities of trusted contacts. They then capture the login credentials, using this data to install backdoors without even having to engage with the user.

Once hackers gain access, they install backdoors in the form of legitimate-appearing software programs or even embed them entirely into the device firmware. So, they can be accessed remotely and even activated to work silently in the background. This gives them access to control the system, steal data, monitor system activity, capture login credentials, intercept communication – the list is endless.

If that wasn’t enough, hackers also embed the backdoor deeply into the system for future backdoors, by either making it appear like a system update or modifying the backdoor itself, thus ensuring long-term control. Such attacks are also more challenging to detect as backdoors appear to be legitimate hardware or software infrastructure.

For instance, the 2020 SolarWinds attack, one of the most widely-known, complex, and longest backdoor attacks, saw hackers insert malware into their Orion software updates. The attack went undetected for months before being discovered by cybersecurity enterprise FireEye in December 2020.

Preventing Backdoor Attacks

Detecting and preventing backdoor attacks is a multi-layered approach, with effective defense strategies combining proactive practices like comprehensive user training and regular system updates with out-and-out technical measures such as intrusion detection. Regular security audits are necessary to detect vulnerabilities, discrepancies, and unauthorised changes to the network.

Setting up intrusion detection systems allow enterprises to monitor network traffic and stay on the lookout for suspicious patterns and departures from usual network behaviour, such as sudden access attempts or data transfers from unauthorised devices. Advanced endpoint protection, most of which use ML (machine learning) and AI (artificial intelligence) today, is critical, as they can detect and block both suspicious and known malware behaviour.

Perhaps one of the most important methods to keep backdoor attacks at bay is regularly updating and patching all hardware and software to shut down known vulnerabilities. And, of course, nothing can replace educating and training users to not only practise good password hygiene but also be able to identify phishing attacks. Since educated users are on guard, they greatly minimise the risk of hacks involving human error, thus elevating overall security.

Final Thoughts

Backdoor attacks are not only an evolving cybersecurity threat, but also a rather persistent one. As backdoor cybercrimes get increasingly sophisticated and refined, the goal is to remain proactive in securing systems, activating advanced threat detection and intrusion systems, installing strong authentication measures and zero trust architecture, and conducting regular software updates.

Only an approach as multi-layered and comprehensive as this will promise to be a great defense against what is one of the most persistent threats to network security.

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