How to deal with insider threats?

“Your ISO 27001 is nice in theory, but if our system administrator goes crazy, we’re dead.” – I hear this quite often when speaking to my clients about which security controls they should apply.

And it’s not only system administrators, it is also the line managers, engineers, top management, etc. – actually, anyone who has access to sensitive information or systems could be a potential threat. For instance, the biggest damage in banks is not done by robbers (with guns in their hands), but by inside jobs (with computers in their hands).

Of course, money theft is not the only purpose of these kinds of attacks – it can also be sabotage, theft of confidential corporate information, altering of data, theft of identities, etc.

Since this is such a complex issue, how can you deal with it?

Risk assessment

ISO 27001 is a standard which approaches security management mainly from the preventive point of view – the first step is to find out which incidents could happen regarding your employees (but also external partners with access to your systems), and then to choose appropriate security controls in order to avoid those incidents. In ISO 27001, this process is called risk assessment and risk treatment.

However, risk assessment shouldn’t be done superficially. If you didn’t think really hard about all the bad things that can happen, then you won’t mitigate those risks and someone could exploit those vulnerabilities.

Therefore, don’t rush through this step; do it systematically.

Preventive measures

Once you know how an insider can exploit your vulnerabilities, you can start planning your security controls in a comprehensive way. Again, ISO 27001 offers a catalogue of security controls in its Annex A – here are a few examples of the most common controls to mitigate the risk of insider threats:

  • Access control (section A.11 in Annex A) – access to sensitive data can be approved on a need-to-know bases only. This way you decrease the number of people that can do harm, but also decrease the damage if someone’s identity is stolen.
  • The access privileges must be regularly reviewed (control A.11.2.4) – very often quite a few employees have access to information they don’t really need.
  • The accounts and access rights of former employees must be removed (A.8.3.3) – yes, sometimes there are open accounts a few years after an employee has left the company…
  • Strong password policy (control A.11.2.3) or some other authentication method should be enforced to disable identity theft.
  • Segregation of duties (control A.10.1.3) – you probably wouldn’t allow a single person to authorize large payments – the same goes for any other sensitive system.
  • Backup (A.10.5.1) – of course, it should be regular; but also access to backup information cannot be allowed to employees who can harm your production systems the most.
  • Document policies and procedures which clearly define the security roles and responsibilities (A.8.1.1; A.10.1.1) – you cannot expect your employees to observe the security rules if they don’t know what the rules are.
  • Awareness & Training (A.8.2.2) – all of your employees need to know why it is necessary to protect sensitive data, as well as how to do it; for certain jobs (like monitoring logs) you may need to send your employees to special trainings.

Of course, there are other controls that are more technically oriented, like segregated network architecture (A.11.4.5), regular security patches (A.12.6.1), spyware scanning (A.12.5.4), anti-virus (A.10.4.1), firewall (A.10.6.1), physical entry controls (A.9.1.2), etc.

People issues

However, someone with high motivation and skills can bypass all of these security controls and achieve whatever agenda he or she has. Therefore, in my opinion, the most important thing is to develop some early warning indicators. And that requires a little bit more sophistication.

First of all, you need to know who you are employing – you probably wouldn’t allow some total stranger to access your sensitive data and/or systems only because he or she has a very nice diploma and a letter of recommendation. You need to dig deeper, or as ISO 27001 puts it – perform the background verification checks (A.8.1.2).

The second, and probably the most important control, is to constantly monitor what is going on – both on the “soft” side (most of the times you can observe if someone is starting to behave in a strange way) and on the “hard” side – by monitoring logs (A.10.10.2), i.e. monitoring whether there is anything suspicious in the use of information systems. Actually, the two can often be viewed together – whenever you conclude that someone’s behavior is peculiar, then this person’s logs need to be observed in more detail. And vice versa – if you spot some strange usage of information system, the soft side should be monitored more closely.

To conclude, insider threats will probably remain the biggest risk to the security of information – the complexity of information systems and amount of data will only increase this threat in time. And the best way to deal with them is to prevent them – once they happen, you can only hope they won’t go too far.

To help you establish good security practices within your company and raise awareness about the threats throughout different departments, try this free online Security Awareness Training.

Advisera Dejan Kosutic
Dejan Kosutic
Leading expert on cybersecurity & information security and the author of several books, articles, webinars, and courses. As a premier expert, Dejan founded Advisera to help small and medium businesses obtain the resources they need to become compliant with EU regulations and ISO standards. He believes that making complex frameworks easy to understand and simple to use creates a competitive advantage for Advisera's clients, and that AI technology is crucial for achieving this.

As an ISO 27001 and NIS 2 expert, Dejan helps companies find the best path to compliance by eliminating overhead and adapting the implementation to their size and industry specifics.
Connect with Dejan: