Today’s increasingly tech-savvy CEOs have a lot of questions for chief information security officers (CISOs). How do we know whether the IT environment is protected? Are my personal data and accounts secure? Why do you need more budget when we’ve already invested so much in security?

For years, defense in depth was the answer to these and myriad other pointed questions from business leadership. But in today’s threat landscape, where many cybercriminals are sophisticated enough to circumvent layered safeguards, the old defense-in-depth philosophy is due for an upgrade.

What Is Defense in Depth?

Defense in depth is a military strategy designed to create layers between an attacker and their primary goal — which, in the context of enterprise cybersecurity, is usually the company’s most valuable assets. If one layer is broken, the next layer will take over.

When implemented correctly and maintained properly, defense in depth leads to a reasonable level of security. However, the bad guys are also aware of this philosophy, and they are constantly changing their strategy to overcome it, shifting between various targets and techniques. Depending on how long it would take to update or replace layers of a defense-in-depth infrastructure, it may not be enough to stave off advanced threats.

What Does Security in Depth Look Like?

Security in depth means simply adding another layer to the defense-in-depth philosophy. This layer will not provide additional security in terms of real-time detection, but it will reveal more insights in the overwhelming log data.

Attackers usually leave breadcrumbs before a major attack. By applying data science techniques, security teams can discover these hidden breadcrumbs and, depending on their contents, take appropriate action. It is not uncommon for an attacker to conduct malicious activities for more than 180 days before being discovered.

Shifting Focus to Data Science

A security-in-depth strategy requires a new set of skills, namely data science. A data scientist slices and dices available log data to discover hidden breadcrumbs. In many cases, this specialist works closely with a threat hunting team because this team is well-informed about what is happening — not only in the outside world by monitoring security forms, the darknet, vulnerability vendors and more, but also within the company if they are part of the change advisory board. Any new change in the IT/OT landscape, they should be aware. These changes can require the built models to be updated to reduce false positives.

Demonstrate Security ROI

When security in depth is actively applied, it is easier to determine the value of each security investment. When an investment is made and the underlying techniques become obsolete, it’s easier to identify them so a replacement program can be initiated. It’s also easier to identify potential security gaps. Depending on your risk appetite, these security gaps should be dealt with as early as possible.

Is Security in Depth Compatible With SIEM?

When you implement a security-in-depth strategy, does that automatically render the installed security information and event management (SIEM) tool obsolete? No, because the SIEM solution will continue to provide value in terms of near real-time detection, depending on the quality of the implemented use cases. However, it’s possible that the SIEM solution will have too little or incomplete log data available, so it will not be useful to data scientists searching for breadcrumbs.

Data scientists require an extensive set of log data; ingesting everything into a SIEM can be too costly. In that case, a less expensive security information management (SIM) solution that provides a good set of APIs to extract a selective part of the ingested log data may be a more attractive option.

Help Your CEO Get Some Shut-Eye

The security-in-depth philosophy is about analyzing available and ingested data with a data science approach to reveal attackers’ activities and intentions. It is also designed to determine whether existing layers of the defense-in-depth infrastructure are still working. Finally, security in depth gives CISOs the information and context they need to demonstrate return on investment to business leaders. With this enhanced visibility and all the security data they need at their fingertips, CEOs can rest easy that their business is secure and prepared to quickly recover from a cyberattack.