10 Insider Threat Examples: Real Corporate Case Studies

The external threat is a visible storm; the insider threat is a slow leak in the heart of the ship. 

In 2025, the average annual cost of insider threats surged to a staggering $17.4 million per organization. Insider threats aren’t a mere isolated event; they’re often clever and, at times, accidental. Using inside knowledge and access, insiders leave a trail of stolen data, stopped progress, and broken trust, reminding us that the greatest vulnerability often lies within.

Insider threats can take many forms, whether a frustrated employee deletes critical systems, a trusted contractor sells trade secrets to a competitor, or even a manager tricked into revealing sensitive info. The biggest insider threats in history didn’t just disrupt; they provided critical examples of the surprising ways people can harm an organization from the inside.

Here are the most damaging real-world insider threat cases, categorized by their primary impact on organizations, from data leakage and intellectual property theft to operational disruption and credential compromise. Each of these categories represents a critical vulnerability, which is why a growing number of businesses now rely on insider threat management software to mitigate these specific risks. 

10 real-world insider threat examples: At a glance

Real-world insider threat examples by impact

Think the biggest threats come from outside? Think again. An inside job can be devastating. Here are a few real-world examples that show the financial, operational, and reputational damage an insider can really do.

1. Tesla (2023): 100 GB of employee data leaked

In 2023, Tesla was breached by two former employees who leaked 100 gigabytes of confidential data to the German newspaper Handelsblatt. The former employees exploited their internal access to Tesla's IT systems to extract and publish the data. The leaked information included sensitive personal data of over 75,000 current and former employees, such as names, addresses, phone numbers, email addresses, and Social Security numbers. The breach also exposed customer bank details, production secrets, and internal complaints about Tesla's full self-driving features.

Tesla responded by filing lawsuits against the individuals responsible and obtaining court orders to prevent further misuse of the data. The company also offered complimentary credit monitoring and identity theft resolution services to affected parties. 

This incident underscores the importance of implementing robust data access controls, continuous monitoring of employee activities, and legal measures to prevent insider attacks. It also highlights the critical risks associated with former employees retaining access or knowledge that can be exploited post-employment.

2. Yahoo (2022): 570,000 pages of trade secrets stolen

Qian Sang, a senior research scientist at Yahoo, stole 570,000 pages of confidential information about Yahoo's AdLearn product, including source code, backend architecture information, secret algorithms, and other intellectual property. 

Yahoo claims that it downloaded this massive volume of data to his personal storage devices 45 minutes after receiving a job offer from one of Yahoo's competitors. This was done without authorization. The stolen data also included strategy documents and a competitive analysis of The Trade Desk, a competitor. He received a significant raise, a six-figure signing bonus, and a substantial stock plan from the competitor.

Yahoo subsequently filed three charges against Sang, including intellectual property data theft. The legal action aims to secure $5 million for Yahoo, with a further demand for punitive damages intended as a penalty. Sang's actions were directly tied to a new job offer from The Trade Desk, a direct competitor of Yahoo, a classic example of corporate espionage, where a trusted insider compromises proprietary data for the benefit of a rival.

This event shows the weaknesses of traditional security tools. DLP software solutions often can't detect data hidden in compressed files, while behavior analytics can trigger too many false alarms. This underscores the need for more advanced ways to prevent data theft, especially for employees in sensitive roles like R&D who are about to leave the company.

3. Google Waymo (2016): Cloud misconfiguration leads to massive data theft

Anthony Scott Levandowski, a former Google engineer, attempted to steal trade secrets belonging to Google, including critical data on laser pulse driver designs, circuit designs, and instructions for calibrating LiDAR lasers. He downloaded approximately 14,000 files, totaling 9.7 GB, related to self-driving car technology before leaving to launch Otto, which was soon acquired by Uber. 

Google filed a lawsuit against Uber for trade secret theft. Levandowski was indicted on 33 counts of trade secret theft, facing 18 months in prison. The court also ordered him to pay a fine of $95,000 and $756,499.22 in restitution to Waymo LLC, as Google’s self-driving program is now known. Google estimated losses of up to $1.5 million due to the theft. The case set a broader trend of engineers stealing self-driving trade secrets across the industry.

What happened made clear that industries characterized by rapid innovation and high-value intellectual property are particularly subject to this type of insider threat. Companies in competitive sectors must implement high security, including strict access controls, continuous monitoring of data access and transfer patterns, and advanced DLP solutions that can identify and block unauthorized transfers of specific types of sensitive data.

Legal and technical measures must be integrated to protect the company's "crown jewel" (its most valuable asset), whether intellectual or physical.

4. Anthem (2015): Breach results in  record $115 million class-action settlement

The attack began with a phishing operation that targeted Anthem employees. Hackers gained access to at least five employees’ credentials, including those of a systems administrator, allowing them to infiltrate Anthem’s internal systems. Leveraging these stolen credentials, the attackers moved laterally within the network to eventually access and steal sensitive data belonging to approximately 78.8 million customers and employees, making it the most prolific healthcare data breach at the time. 

The stolen data included names, dates of birth, addresses, telephone numbers, email addresses, income data, and Social Security numbers. Anthem paid $115 million to settle a class-action lawsuit, which was the largest data breach settlement in history for health records at that time. $16 million HIPAA settlement was done with the Department of Health and Human Services, also a record amount under federal law. The incident caused significant operational challenges and severe reputational damage. Anthem offered identity protection and credit monitoring services to the affected individuals.

Organizations, especially those holding vast amounts of personally identifiable information (PII) or sensitive data, must recognize that their employees are prime targets for sophisticated social engineering. Implementing strong multi-factor authentication (MFA), comprehensive security awareness training focused on phishing, and advanced threat detection systems capable of identifying lateral movement and dormant accounts are crucial.

5. NSA (2016): Leaked hacking tools cause billions in worldwide damages

An unidentified hacker group known as "The Shadow Brokers" leaked a collection of highly sophisticated hacking tools allegedly developed by the NSA's Equation Group. To this day, the exact origin of the leak remains unconfirmed, with U.S. officials not publicly concluding whether the tools were stolen by a malicious insider or obtained through an external compromise of NSA servers. 

These tools included zero-day exploits such as "EternalBlue," which targeted a wide range of systems, including enterprise firewalls, antivirus software, Microsoft products, routers, and Linux mail servers.

The leaked tools were subsequently used in massive global cyberattacks, most notably the WannaCry ransomware attack, which affected over 200,000 computers across 150 countries and caused billions of dollars in damage. The exploits were also utilized in the NotPetya cyberattack. The leak forced security companies across the industry (e.g., Cisco, Juniper, Fortinet) to urgently investigate and patch their hardware and software solutions.

This whole incident was a huge wake-up call. It showed just how important it is to lock down powerful cyber tools. The moment they leaked, less-skilled hackers started using them, and suddenly, almost everyone was at risk.

6. Cisco (2018): Insecure cloud access leads to major service outage

Sudhish Kasaba Ramesh, a former Cisco employee, used malicious code to automatically delete 456 virtual machines that supported Cisco's WebEx Teams conferencing software. Ramesh gained unauthorized access to Cisco's cloud system over four months after he had resigned from his role. He leveraged network access retained from his employment and deployed the malicious code from his own Google Cloud project. 

The incident suggests a potential lack of robust multi-factor authentication or other stringent access management methods on sensitive resources. 

The attack rendered 16,000 WebEx Teams accounts unreachable, with some shut down for a period of two weeks. It cost Cisco approximately $1.4 million to remediate the incident and compensate affected customers. While there was no data loss, the incident resulted in significant operational disruption and financial losses. Ramesh was sentenced to two years in prison and ordered to pay a $15,000 fine for his actions.

The core takeaway from this incident is the serious risk posed by insecure multi-cloud access. It shows how a malicious actor can use credentials from one cloud platform (retained access to Cisco's AWS) to launch an attack from an entirely separate one (a personal Google Cloud account). This drives home a critical point: when an employee leaves, it’s absolutely essential to revoke their access everywhere, across all cloud services. And beyond that, companies need to actively monitor for unusual cross-cloud activity that could signal a breach in progress.

7. Twitter (2020): High-profile hack causes loss of over $100,000 worth of bitcoin

A coordinated social engineering attack compromised several high-profile Twitter accounts (including Barack Obama, Joe Biden, Bill Gates, Apple, and Uber) to promote a bitcoin scam. The scam tweets promised to double any bitcoin sent to a specific cryptocurrency wallet.  

The attack was carried out by a 17-year-old actor and his accomplices. They gained access to Twitter's internal administrative tools by successfully social engineering Twitter employees who had access to these systems. This involved an initial breach of lower-level employee credentials, followed by further social engineering to obtain credentials for the admin tools.

The attack vector was linked to Twitter's remote working arrangements during the COVID-19 pandemic, with information and authorization processes for remote access being exploited from internal Slack channels. Twitter later confirmed it was a "phone spear phishing attack". A significant vulnerability was the broad access (up to 1500 employees and partners) to administrative tools capable of resetting accounts.

The scam resulted in loss of over $100,000 worth of bitcoin. It caused massive reputational damage to Twitter, described as "the worst hack of a major social media platform yet" by Dmitri Alperovitch. The incident led to operational disruptions, including Twitter temporarily disabling the ability for some accounts to tweet or reset passwords. Twitter's stock price fell by 4% immediately after the incident. Concerns were also raised about national security implications due to Twitter's importance for political discussions.  

This breach displays a need for social engineering defenses, stringent access controls for privileged accounts, and continuous monitoring of employee behavior with employee monitoring software, especially in remote work environments.

8. City of Calgary (2016): A Single email compromises the personal information of thousands

An employee of the City of Calgary, Alberta, accidentally leaked the personal information of more than 3,700 employees. The breach occurred when the employee sent the sensitive information via email while seeking technical assistance. This was a simple human error in handling sensitive data.

The City of Calgary is facing a $92.9 million class-action lawsuit following the privacy breach. Such incidents can lead to reputational damage and potential legal liabilities.  

The fallout from this incident makes it evident that even seemingly minor human errors in everyday tasks can lead to significant data exposures. It reinforces the need for continuous employee training on secure data handling practices and the importance of data classification to identify and protect sensitive information.

9. OPM data breach (2015): Sensitive data compromised

In April 2015, the U.S. Office of Personnel Management (OPM), the agency that manages the government’s civilian workforce, discovered that some of its personnel files had been hacked. 

The attackers gained valid user credentials of a government contractor that conducted background investigations for OPM, likely through social engineering. They exploited numerous vulnerabilities due to outdated software, insufficient cybersecurity protocols, and a critical lack of multi-factor authentication for all employees and contractors. 

The attackers installed malware and created backdoors, escalating privileges to obtain Windows domain administrator credentials for persistence. OPM also suffered from fundamental IT security failures, including a lack of a comprehensive inventory of systems, expired security agreements, and a poorly architected network.

This was one of the largest breaches of government data in U.S. history, resulting in the compromise of sensitive information for 21.5 million individuals. The stolen data included the fingerprint data of 5.6 million people. 

Crucially, the attackers exfiltrated millions of SF-86 forms, which contain extremely personal information gathered in background checks for people seeking government security clearances. This caused significant national security concerns due to the compromise of intelligence and military personnel. The devastating fallout led to a Congressional investigation, the resignation of top OPM executives, multiple class-action lawsuits, and a proposed settlement, with OPM offering identity monitoring and other services for at least 10 years.

As detailed in the official Congressional report, this development acts as a wake-up call regarding the critical importance of basic cybersecurity hygiene, especially within government agencies holding sensitive data.

10. Capital One data breach (2019): Private information of 100 million people leaked

Paige Thompson, a former Amazon Web Services (AWS) employee, stole the private information of over 100 million people, including millions of credit card applications, 140,000 Social Security numbers, 80,000 bank account numbers, and 1 million Canadian social insurance numbers.

Thompson also allegedly copied data from at least 30 other entities using the same cloud provider. Thompson used a tool she built to scan AWS accounts for misconfigured web application firewalls (WAFs) on rented servers. This allowed her to send commands that revealed account security credentials, which she then used to access and download data.

As a result of the breach, Capital One faced significant financial penalties. The company agreed to pay $190 million to settle a class-action lawsuit filed by customers, which was in addition to an $80 million fine it paid to federal regulators in 2020. The breach also caused significant reputational damage, and the perpetrator, Paige Thompson, was charged with wire fraud and computer crime and sentenced to 5 years of probation, including location and computer monitoring.

This case highlights the importance of proper cloud security configurations, continuous monitoring for misconfigurations, and the inherent risk posed by individuals with deep technical knowledge of specific platforms, even after their employment ends.

What's the worst that can happen? A list of insider threat damage

Insider threats are often underestimated until one hits. The next set of examples showcases the actual fallout organizations have faced when insider defenses failed — or didn’t exist.

• Edward Snowden (NSA, 2013): A government contractor leaked millions of classified documents, exposing global surveillance programs and causing a massive international diplomatic crisis.
• Marriott (2018): Attackers compromised the Starwood guest reservation system in 2014 and remained undetected for four years, accessing data on 500 million guests.
• Lockheed Martin (2011): Sophisticated attackers used spear-phishing to compromise employee accounts, stealing SecurID token data to breach the defense contractor's secure network.
• General Electric (2020): An engineer stole terabytes of valuable trade secrets related to advanced turbine technology over an eight-year period to benefit his own competing business.
• AT&T (2021): Employees were bribed by a criminal organization to install malware on the company's internal network and unlock over two million phones.
• Suntrust Bank (2018): A former employee potentially stole and attempted to share the contact information of 1.5 million clients with a criminal third party for financial gain.
• Ubiquiti (2021): A senior developer stole gigabytes of confidential data and then attempted to extort the company for millions of dollars by posing as an external hacker.

Insider threat prevention checklist

Your strongest security is only as good as your internal defenses. Insider threats are a persistent and complex challenge, but they can be managed. This essential checklist provides the foundational steps to minimize internal risks and safeguard your most valuable assets.

• Grant users only the minimum access necessary for their specific job role.
• Enforce MFA on all accounts to prevent unauthorized access.
• Immediately revoke all system and physical access upon an employee's departure.
• Monitor all user network activity for anomalies like mass data downloads or unusual login times.
• Use DDLP tools to automatically block unauthorized data transfers.
• Continuously train all employees to recognize and report phishing attempts and security threats.
• Tightly control and audit all privileged administrator accounts.
• Classify sensitive data to ensure critical assets receive the strongest protection.
• Establish a dedicated team from HR, Legal, and IT to manage insider risk.
  Regularly audit user permissions to remove outdated or excessive access rights.

An ounce of prevention is worth a terabyte of cure.

All these stories show that a company's biggest security risk can come from its own people. An insider can be many different types of people. It might be an angry employee seeking revenge, someone trying to get rich by stealing secrets, or even a good employee who makes an honest mistake.

This threat is so dangerous because insiders are already trusted. They don't need to hack into the company because they already have the keys. They know exactly where the important information is and how to get it.

To solve this problem, companies can't just focus on blocking outsiders. They must also pay close attention to what's happening on the inside. This means being smart about who can see what information, watching for unusual activity, and teaching everyone how to be more secure. In the end, protecting against the insider threat is about building a safe and careful work environment for everyone.

What all these examples have in common is that the threat came from a place they least expected. Yesterday's security strategies are clearly no longer enough. To truly future-proof your organization, you need to shift from a reactive to a proactive defense, which is fueled by understanding the threat landscape. 

Dive deeper into the most common network security threats and how businesses can defend against them.