What Is An Insider Threat? Definition & Examples | Proofpoint US

An insider threat is when someone misuses their authorized access to negatively impact a company’s critical information or systems. This person does not necessarily have to be an employee. Third-party vendors, contractors, and partners could also abuse their access.

“Insider threats arise from careless users, users with compromised credentials, or users who seek to cause harm intentionally,” says Stephanie Torto, Senior Product Marketing Manager at Proofpoint. “The latter type of user—the malicious insider—can be the most daunting for security teams to manage. It requires them to analyze a user’s behavior and determine whether they have bad intentions.”

Malicious insiders abuse their access for personal gain, revenge, or competitive advantage—stealing intellectual property, selling confidential data, or sabotaging systems. Current statistics show that 74% of cybersecurity professionals are most concerned with these intentional bad actors, a significant increase from 60% just five years ago. Financial gain drives 89% of malicious insider breaches, though workplace grudges, espionage, or ideological beliefs also play a role.

However, malicious intent is not the only driver of insider threats. Negligent insiders create security risks through careless actions, poor security practices, or simple human error—like clicking phishing links, misconfiguring systems, or accidentally sharing sensitive data. Compromised insiders are another category where external attackers exploit legitimate credentials through techniques like credential theft or social engineering to gain insider access.

What Is an Insider?

An insider is any person who has or had authorized access to or knowledge of an organization’s resources, including personnel, facilities, information, equipment, networks, and systems. This definition extends beyond traditional employment relationships to encompass anyone granted trust and access by the organization.

According to CISA, an insider is someone the organization trusts with sensitive information, access privileges, or knowledge that could potentially harm the organization if misused. The key difference is not employment status, but the level of access and trust given to the individual; a current or former employee, contractor, or business partner who has or has had authorized access to the organization’s network, systems, or data. Examples of an insider may include:

• A person the organization trusts, including employees, organization members, and those to whom the organization has given sensitive information such as financial data, business strategy, and organizational strengths and weaknesses.
• A person given a badge or access device identifying them as someone with regular or continuous access (e.g., an employee or member of an organization, a contractor, a vendor, a custodian, or a repair person).
• A person to whom the organization has supplied a computer and/or network access.
• A person who has intimate knowledge about and possibly helps develop the organization’s products and services; this group includes those who know the secrets of the products that provide value to the organization.
• A person who is knowledgeable about the organization’s fundamentals, including pricing, costs, and organizational strengths and weaknesses.
• A person who is knowledgeable about the organization’s business strategy and goals, entrusted with future plans, or the means to sustain the organization and provide for the welfare of its people.
• In the context of government functions, the insider can be a person with access to protected information, which, if compromised, could cause damage to national security and public safety.

Insiders aren’t just current employees. The classification extends to anyone with physical or digital access to sensitive areas, third-party vendors who understand your internal processes, and individuals who’ve developed deep institutional knowledge about how your organization operates.

Here’s the critical part: former employees, terminated contractors, and ex-partners remain insider threats long after they’ve left your organization. If they still possess organizational knowledge or retain any residual access, they represent ongoing security risks that many companies overlook.

What makes insiders so dangerous? Unlike external attackers, insiders operate from a position of trust with legitimate access. This allows them to sidestep traditional security controls designed to keep outsiders at bay. Their combination of trusted status and intimate knowledge of organizational vulnerabilities creates a perfect storm—they know exactly where your weak spots are and have the access to exploit them, whether intentionally or accidentally.