When most people think of a data breach, the image that comes to mind is often a hooded hacker typing away in a dark room. But the reality is far more unsettling—the biggest threat to an organization’s security may be sitting just a few desks away.
A staggering 95% of all cybersecurity incidents can be traced back to human error. These aren’t always the result of complex malware or state-sponsored attacks, but everyday mistakes made by employees. And the cost of these errors is enormous. In 2024, the average cost of a single data breach climbed to nearly $5 million—a devastating price for a moment of carelessness or one poor decision.
If firewalls and technical defenses aren’t the only weak spots, where is the real danger coming from? The answer lies with insiders—the very people already inside the company walls.
The most common insider threat is the accidental kind. These employees aren’t malicious; they’re often hardworking, well-meaning individuals who make mistakes or are misled. Accidental insider threats typically fall into two categories:
In one of the most well-known incidents, Snapchat fell victim to a simple phishing scam. A payroll employee received a convincing email that appeared to be from the CEO requesting payroll data. Wanting to be helpful, the employee complied—unknowingly handing over the personal information of 700 staff members.
All the company’s technical defenses were bypassed by a single fraudulent email, proving the critical importance of employee training.
In another case, an employee intended to send a spreadsheet internally but accidentally sent it to an external contact. Unfortunately, the file contained sensitive data—including medical records and home addresses—of thousands of employees. That single misclick led to a massive class-action lawsuit, demonstrating the enormous risk posed by even small human errors.
While accidental mistakes are damaging, malicious insiders represent an even darker risk. These individuals deliberately exploit their access for personal gain or revenge. They typically fall into two categories:
An IT engineer at Intervest, an energy company, learned he was about to be fired. With administrator-level access, he retaliated by wiping critical servers, destroying years of data. The company was offline for an entire month, and the financial and reputational cost was catastrophic. Though the engineer was later sentenced to four years in prison, the damage to the company was permanent.
An internal auditor at Morrison’s, a UK supermarket chain, leaked payroll data for 100,000 employees after a workplace dispute. The information—including bank details and salaries—was posted publicly, triggering widespread panic and years of costly legal battles. This case illustrates just how much power a single trusted employee can hold.
So, what can organizations do to protect themselves? The answer lies in creating a human firewall—strengthening the people side of cybersecurity with proactive strategies. Four key steps are essential:
Each of these solutions directly addresses the real-world case studies we’ve explored: training defends against phishing scams, access controls reduce revenge-driven sabotage, and monitoring helps catch unusual activity before it spirals out of control.
The ultimate takeaway is this: adopting a Zero Trust mindset is no longer optional—it’s essential. This doesn’t mean distrusting your employees, but rather verifying access and monitoring activity consistently. Trust your team, but always verify.
Because in the modern cybersecurity landscape, the greatest risk often isn’t outside the walls—it’s already inside.