The enemy you know: an analysis of the insider threat



Many organisations are already cognisant of the fact that there are security threats originating from the inside, beginning with their own trusted employees and partners. However, many organisations do not necessarily differentiate between the various types of internal adversaries, and may also be unaware that a uniform defence posture is not effective, as different defence strategies are required to thwart each type of adversary. This article will analyse the different types of internal threat actors, and discuss how each is defended against. It will consider both technology and psychology solutions, and aim to do so in a way that is immediately actionable for organisations of all types.

Threat modelling

Any discussion of security strategies would be incomplete without an understanding of how those strategies relate to an organisation’s threat model. All companies must define their threat model, which effectively articulates assets, adversaries and architecture. When considering assets, the organisation must understand not only which assets are worth protecting, but must also quantify those assets in terms of both the downside to the company, and the potential upside to the adversary in the event of asset compromise. It is important to note that those two metrics are not necessarily the same. Once an organisation understands the value of their assets, the organisation can then clearly understand who the adversaries are that would be interested in attacking in order to compromise the assets. Once assets and adversaries are understood, the organisation is then best able to articulate the defence architecture that is most effective.


In order to fully understand internal adversaries, one must first consider external adversaries. In the context of most industries, there are four primary categories of external adversaries. Casual hackers are those motivated by notoriety; they steal assets so they can brag about it and obtain credibility from their peers. Hacktivists, including groups such as Anonymous, attack companies in order to make political statements. Organised criminals make business decisions, and steal assets in order to make money. Nation states attack to pursue geopolitical and economic interests.

When analysing the difference between external adversaries and internal adversaries, it is important to remember that these terms are not opposite within this context; rather, the difference between external and internal lies in conditions of trust and access. Internal adversaries could be extensions of the external adversaries discussed above, but they have additional trust and access typically granted to employees and other insiders. Internal adversaries are broken into three different types of actors: accidental, opportunistic and determined. The defences against these, by way of technology and psychology solutions, break down into prevention, deterrence or mitigation.

Accidental insider

The accidental insider harms the company not with malicious intent, but simply as a result of poor decision making. Fundamentally, people are an organisation’s weakest link. People create weak passwords and reuse them across different services, people lack discretion when clicking links in emails or inserting random thumb drives; and people are notoriously susceptible to social engineering attacks. All of these conditions lead to otherwise trusted employees unwittingly turning into the accidental insider.

An organisation’s best defence against the accidental insider is through prevention, whereby the organisation mitigates damage in the event that the trusted insider unwittingly compromises assets. Encryption and multi-factor authentication are a few good examples of technology solutions that are effective in minimising the damage done by the accidental insider. Training is an effective psychology solution against this type of adversary, whereby the organisation helps its people become better educated about how their actions can deliver significant harm to the organisation.

Opportunistic insider

The primary defining characteristic of the opportunistic insider is that he or she will compromise an asset when there is no repercussion for doing so. The opportunistic insider may not initially set out to harm the company; rather, over the course of performing his job duties he might be granted access to a valuable asset from which he may benefit by compromising, perhaps achieving financial gain by selling it or obtaining notoriety for being the first person to leak it. Without a disincentive in place, this employee may choose to pursue these gains.

Organisations can best defend against the opportunistic insider through deterrence. If this type of adversary thinks he will be caught, he is far less likely to compromise the asset. Logging, monitoring and digital rights management are a few examples of technology solutions that are effective against this type of adversary, as such tools create a trail that leads back to them directly. The most effective psychology solution against this type of adversary is awareness. It is important to make the distinction between training and awareness – while training seeks to educate employees about their individual actions, awareness seeks to galvanise the group of employees to protect assets together. If the opportunistic adversary thinks they are being observed by their colleagues, they are less likely to compromise assets.

A great example of this comes from psychologist Thomas Moriarty through his experiment colloquially referred to as the ‘Beach Blanket experiment’. In this landmark study of group dynamics, Moriarty researched how bystander involvement affects theft deterrence. His researchers found that when bystanders were asked to be involved in the protection of an asset, the instances in which they took action skyrocketed, quoting that “results support the notion that prior commitment simplifies the decision process and produces a more responsive bystander”. This premise readily applies to the concept of awareness, whereby teaching employees about how and why to be observant of their workplace, co-workers and assets will reduce the instances of attacks by the opportunistic insider.

Determined insider

The determined insider is the most dangerous category of internal adversary, because the determined insider is motivated to harm the company. There are two notable subgroups within this adversary category: disgruntled insider and malicious insider. The disgruntled insider has become dissatisfied with the company for reasons such as being passed over for a promotion or by becoming disillusioned with the corporate mission. The malicious insider is an agent for one of the external threats previously mentioned. What makes the determined insider especially dangerous is that because he is motivated by malice the aforementioned technology and psychology solutions against the other internal adversaries are ineffective. For instance, the disgruntled insider knows what he is doing will harm the company but proceeds anyways, and so training and even awareness will not necessarily stop him.

Mitigation is the best defence against the determined insider, whereby the organisation assumes the posture that the adversary has already compromised an asset and makes it difficult for the adversary to compromise additional assets. One effective solution against this type of adversary is separation of privileges. Through privilege separation, an organisation reduces any particular user’s privilege to the absolute minimum that still enables the user to be successful at their job. When done properly, privilege separation sets up employee roles like a chessboard – a large number of weak user roles (pawns), a small number of semi-powerful management roles (rooks) and a very limited number of all-powerful admin roles (queen). By limiting the power of most roles, this decreases the likelihood that the determined insider adversary would be powerful. It is important for organisations to remember that even well-designed privilege separation must be implemented properly, in such a way that low level users are not able to escalate privileges into more powerful admin roles.


The internal threat is a real adversary who can do significant damage to most organisations. By understanding the distinctions between the different types of internal adversaries, organisations can design and implement an effective suite of defences to counter each type of foe.


Ted Harrington is the executive partner at Independent Security Evaluators. He can be contacted on +1 (443) 270 2296 or by email:

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Ted Harrington

Independent Security Evaluators

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