What is a backdoor attack?
A backdoor attack is hard to detect. Since they bypass standard security measures, backdoor attacks can enter your system and go unnoticed for a long time. While some cyberattacks tend to be smash-and-grab, backdoor attacks are stealthier. They allow hackers to enter secretly, gather more secure data than typical attacks, and can cause significant damage. Because they can be so difficult to detect and cause so much damage, you need to know the signs of a backdoor attack and learn how to mitigate it.
What is a backdoor?
A backdoor is a method of bypassing normal authentication or security controls in order to gain unauthorized access to a system, network, or application. They allow remote access to a device in your network.
A backdoor is not inherently bad, they can help IT teams with maintenance and troubleshooting. However, they are typically used for nefarious purposes. Once a hacker gets backdoor access to a device, they can spread to other devices and systems. In some of the most extreme cases, they compromise customers' devices.
How do hackers use backdoors?
Backdoors give hackers high-level access to systems and networks. Once they gain access, they can steal data and resources. Backdoors also give hackers access to other devices and systems.
Privilege escalation: Privilege escalation is when hackers use a backdoor to move from a low-privilege position to admin/SYSTEM-level control of a network.
Data exfiltration: A major purpose of backdoor attacks is to extract sensitive data over a long period of time without detection. Hackers commonly take credentials, intellectual property, and financial records.
Lateral movement: When someone gains access to an endpoint, they can then pivot from one compromised endpoint to other systems within the network.
Staging further attacks: Backdoor attacks commonly function as a launchpad for future attacks. These commonly include ransomware deployment, web shells, or supply chain attacks.
What are common types of backdoor attacks?
A backdoor attack is a method of gaining unauthorized access to a system by passing normal authentication or security controls. There is a range of backdoor attacks and their associated malware. Well-designed ones evade detection for long periods of time, making them especially dangerous.
Trojans: Trojans are malware that install hidden access points once executed. Backdoor Trojans can be especially harmful because they do not present themselves as malicious. Instead, they operate quietly over an extended period of time.
Web shells: Backdoor web shells are malicious scripts that enable hackers to compromise web servers and launch subsequent attacks. Once a web shell is installed, it converts the web server into an interactive command execution environment. Once deployed, it is a permanent backdoor into the targeted web applications and any connected systems.
Rootkits: Rootkits are malware that embed themselves deep in the OS kernel and hide their presence to provide long-term backdoor access to threat actors. They can be especially difficult to detect and even more difficult to remove.
Supply chain attacks: Supply chain attacks target organizations through vulnerabilities in their supply chain network. Unlike direct attacks, which target an organization's own systems, supply chain attacks enter through less secure elements of a network like third-party vendors or software suppliers. They frequently present themselves as software updates.
Worms: Backdoor worms are self-replicating malware that spread throughout a network without user action. They often contain backdoor payloads that provide remote access to multiple systems.
Examples of backdoor attacks
Backdoor attacks are increasingly common and costly. These examples highlight the massive scale of backdoor attacks and how widespread their harm can be.
1. SolarWinds supply chain attack
The 2020 SolarWinds supply chain attack showcased the danger of backdoor attacks. The attack inserted a backdoor into SolarWinds' Orion IT management software. It then injected malicious code called "Sunburst" into a component called SolarWinds.Orion.Core.BusinessLayer.dll. These tainted updates were then distributed to over 18,000 SolarWinds customers. This included numerous government agencies and corporations, allowing the attackers to infiltrate and monitor their networks for months.
2. WannaCry ransomware and the NSA's EternalBlue exploit
In April 2017, hacking group The Shadow Brokers leaked the NSA’s EternalBlue exploit. This targeted a vulnerability in the Windows Server Message Block (SMB) protocol. In May 2017, the North Korean Lazarus Group weaponized this by developing and spreading WannaCry ransomware. This cyberattack impacted over 200,000 devices in over 150 countries. Among the first hit was England's National Health Service. This attack encrypted victims’ files and demanded ransom payments of either $300 or $600 worth of bitcoins.
3. Microsoft Exchange Server data breach
In March 2021, Microsoft Exchange Server had zero-day vulnerabilities exploited. This led to a backdoor installation on over 250,000 servers worldwide. This was done by the Hafnium group and enabled unauthorized access to email accounts and allowed attackers to install additional malware. Acer was among those impacted in the breach. The ransomware gang REvil stole sensitive data from the computer manufacturer's servers. They demanded $50 million and threatened that the ransom would double to $100 million if they didn't pay within 10 days. Although Microsoft released a patch to mitigate the exploited vulnerabilities, the update couldn't close any backdoors that had already taken root.
How can I protect against backdoor attacks?
Because backdoor attacks are executed in such unconventional ways, they can be difficult to spot. Luckily, there are tools and workflows that mitigate the risks and help prevent them from happening.
Unified security information and event management solutions
Unified security information and event management (SIEM) solutions like Log360 provides a range of tools and features to combat against backdoor attacks. By correlating real-time signals across your network, Log360 alerts you of issues like failed logins, abnormal queries, or other signs of backdoor attacks. With prebuilt detection rules, you can protect against backdoor threats like supply chain attacks by continuously monitoring for anomalous behavior through software updates. Tools like user and entity behavior analytics (UEBA) alert your organization to atypical user patterns that may need closer investigation.
Unified endpoint management and security solutions
Unified endpoint management and security (UEMS) solutions helps to detect and block malware and suspicious activity within your network. Many endpoint management solutions like Endpoint Central protect against anomalous activity that leads to backdoors being installed. Endpoint Central protects against backdoor attacks by providing routine patch management. Yet-to-be-patched vulnerabilities are often what backdoors exploit to get installed in the first place, so protect endpoints with patch management plus some endpoint threat detection.
Next-generation antivirus
Traditional antivirus software typically catches viruses that are known to exist. Next-generation antivirus (NGIV) solutions like Malware Protection Plus protect against new and evolving threats that can be harder to catch. This is a helpful defense against backdoor attacks that enter systems through unconventional methods. NGIVs fight backdoor attacks by running network-wide log correlation and using AI and behavioral analysis instead of relying only on virus signatures.
About ManageEngine
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