What if the next data breach in your organization doesn’t come from an external attacker, but from your most trusted employee? Would you be able to detect it in time, or would the surprise leave you unprepared to respond? While firewalls and modern monitoring solutions play an important role in security, they often overlook one critical risk: the insider threat.

What is an insider threat?

An insider threat is an internal actor who can potentially harm the security of an organization. Whether intentional or not, the individual’s authorized access and knowledge can be used in ways that go against expectations and compromise the infrastructure.

In cybersecurity, insider threats are harder to prevent and anticipate than external threats or hackers. This is due to several factors, including risks from unexpected sources, emotionally rooted trust, and actions that appear legitimate yet are harmful.

Types of insider threats

Malicious Insider

The first type that comes to mind! A spy in disguise, spending time faking tasks and gaining trust while secretly serving different intentions.

A malicious insider will intentionally leak sensitive data, sabotage the system, or work with cybercriminals to disrupt confidentiality and availability.

Real-world Example

May of 2023 marked the time of a massive data leak at Tesla. Two former employees leaked more than 75,000 individuals’ personal information, including phone numbers, addresses, social security numbers, salaries, and more.

These two insiders used their legitimate access to internal files and shared them with a German media outlet. While the direct motive is not precise, it’s suggested to be whistleblowing, recognition, or financial opportunities through media exposure.

Negligent insider

While the news often focuses on these stories, the public image of insider threats stays limited to malicious actors, dramatic situations, and strong evil intentions. However, the truth is very different.

In most cases, breaches occur by mistake, caused by a negligent, careless insider.

Here are the human factors at play, and the psychology behind cyber mistakes:

• Long work shifts and heavy responsibilities. These lead to tiredness and burnout, which cause a lack of focus and vigilance.
• Poor security hygiene and lack of knowledge about best practices.
• Pure carelessness and failure to take ownership of the organization’s security.
• Misconfiguration mistakes and unfamiliarity with certain technologies.

Real-world Example

In 2016, Morgan Stanley disclosed that sensitive customer data was exposed due to improper handling of decommissioned IT equipment by a contractor. Devices were retired, and the vendor failed to properly destroy data, making sensitive client information recoverable and affecting millions of customers.

While this incident did not stem from malicious intent, failures in data destruction procedures and operational negligence led to a major breach. As a result, Morgan Stanley was fined millions for failing to safeguard customer data.

Compromised insider

These employees are not malicious, nor are they careless with technology. Instead, they are targeted by external hackers and unknowingly become a gateway into the system. Hackers then gain legitimate-looking access without raising suspicion.

This typically occurs through various techniques aimed at the individual, including malware, phishing attacks, and manipulative social engineering. Rather than attacking the organization’s infrastructure directly, these methods focus on exploiting the employee.

Real-world Example

In August 2022, Cisco disclosed that an attacker gained access to its internal systems after compromising an employee’s personal Google account. Once the account was taken over, the attacker was able to obtain corporate credentials and use them to access internal company resources. Because the activity relied on valid credentials and originated from a trusted identity, it was difficult to distinguish from legitimate behavior.

This incident illustrates how insider threats can emerge without malicious intent from the employee, how identity and credential management failures can collapse trust boundaries, and why detecting compromised insiders remains one of the hardest challenges in cybersecurity.

How to detect and prevent insider threats

Detecting insider threats is not an easy game. These threats originate from normal activities and legitimate operations, unlike the suspicious behaviors SIEMs are designed to detect.

Basic security measures are no longer as effective; organizations must look for behavioral indicators to understand humans and identify potential threats. Such as:

• Employees with poor performance: Those who demonstrate low engagement in their job and show no interest in the organization and its values.
• Members with conflicts: Openly showing disagreements or resentment with policies or company decisions. This often signals potential for revenge actions.
• Former employees: After leaving the company, their accounts and access can become a source of breaches, intentional or not. It should be strictly stopped and monitored.

Tools and strategies to mitigate

• Zero trust: A broad cybersecurity model with the principle: “Never Trust, Always Verify.” It’s a security architecture based on continuous verification and access controls to make sure no user has excessive power that could be misused.
• Least privilege: A core principle that is particularly effective against insider threats, and a specific rule of Zero Trust. Users and systems should only have the minimum permissions needed for their tasks. When a mistake or planned attack happens, damage is contained due to limited access and the inability to escalate.
• UEBA (User and Entity Behavior Analytics): A tool used to collect information about employee activities and study their normal behavior. With behavioral analytics and machine learning algorithms, it analyzes these patterns to detect anomalies and predict potential insider threats.
• SOAR (Security Orchestration, Automation, and Response): A software solution integrated into the SOC teams’ workflow to monitor insider threats. It centralizes alerts, automates incident response plans, and enhances SOC decision-making.
• Security-first culture: From top decision-makers to non-IT employees, security should be embedded in daily operations through training, awareness programs, and ongoing education.
• Strong cybersecurity monitoring: Global comprehensive security oversight is essential for detecting insider threats. Cyber Threat Intelligence tools such as Defendis can help contain data leaks and identify dark web-related threats.

In a nutshell

Insider threats can be more costly and damaging than external attacks. This underscores the need to set your priorities and make insider threat mitigation a top choice. Here are the key ideas to take with you:

• Never trust anyone with systems, including yourself
• Build a strong detection/prevention strategy to stay vigilant
• Avoid excessive restrictions, as productivity must still be preserved
• Never overlook the human factor, including stress, exhaustion, distraction, hidden intentions, and even simple bad days.