An insider threat is a security risk that originates from within your own organization or environment. It typically involves a current or former employee or business associate who has access to sensitive information or privileged accounts within the network or a relative or "friend" who is "unhappy" or careless about something. A high percentage of security-breaches come from within your own environment.
Types of insider threats include:
-In organizations a malicious insider is also known as a Turncloak: someone who and intentionally steals information for financial or personal gains.
-Another insider threat often is a careless person who unknowingly exposes the system or your credentials to the outside world. This is the most common type of insider threat, resulting from mistakes, such as leaving a device exposed or falling victim to a scam.
-A third type of insider threats are "moles": technically outsiders who have insider access.
Insider threats are difficult to find: protective software like firewalls don't pick them up for example, it is for that reason that you will have to take a good look at the behaviour, like someone who logs on to the system from home in the middle of the night or in a more close environment someone who acts differently than they normally did or has a sudden interest in what you are doing, where that interest didn't exist before.
You might want to password-protect your pc and use two-step authentication. Keep your sensitive information in a safe spot and for organizations: tools like Machine Learning (ML) applications can help analyze the data stream and prioritize the most relevant alerts.