Defense In-depth Strategy in Cybersecurity

Cyberattacks increased by 38% in 2022 alone. That trend shows no sign of stopping – which means you should be on high alert to prevent the next data breach from coming your way. Fortunately, certain models will help you fend off most attacks. That’s where defense in-depth comes into play.

Defense in-depth is a cybersecurity strategy that uses multiple levels of security to protect a system. The main gist is to have several layers of defense ready to fend off any cyberattacks launched against an organization. Defense in-depth shouldn’t be confused with layered security.

Is defense in-depth the best security strategy for your company? Is redundancy too much to be worth the effort? Nowadays, no effort is too costly to stop cyberattacks because of the damage they cause, though you can only decide whether it’s worth it once you learn its definition.

Defense In-depth in Cybersecurity: A Definition

A defense in-depth approach is a cybersecurity strategy that uses several methods, products, and approaches to prevent threat actors from succeeding when they launch a cyberattack. In a way, it’s the sum of several tools working together to protect a system or network.

The easiest way to understand the defense in-depth approach is to think about cybersecurity as a fortress. Each tool you use is an extra wall to the fortress, while the fortress is the defense in-depth strategy.

Most experts believe this approach works best to take care of security – because malicious actors often work several angles to launch an attack. You have to think about hardware, software, the human element, and more when it comes to defending your company. You need an approach that protects everything (together and alone) to defend your network.

A small caveat: while often used interchangeably, you shouldn’t confuse defense in-depth with layer security.

Defense In-depth Model vs. Layered Security

  • Defense In-depth. This strategy is the sum of all strategies behind your cybersecurity approach. It requires software, hardware, protocols, guidelines, policies, and anything else you use to protect your network and system as a whole.
  • Layered Security. This strategy requires using multiple resources to defend the same part of your network. For example, protecting company emails requires spam filters, anti-phishing software, antiviruses, and more. These are all tools that create layers to protect the same thing – but they don’t protect the entire system as a whole.

3 Areas Defense In-depth Will Cover

1. Administrative Area

An old truth in cybersecurity explains that the weakest link in every organization is the human element. Employees are more likely to give you up than software or hardware ever will. Sometimes, it’s due to negligence – while other times, we may be talking about insider threats.

Another old truth claims you shouldn’t attribute anything to malice – if you can do it to stupidity. That rings true in cybersecurity too: negligence is the biggest factor behind breaches.

That’s why the administrative area is so important. It covers everything related to employees and the human element: cybersecurity training, guidelines, and policies.

2. Physical Area

How do employees enter the office space? They go through doors. What do they work with? They use data centers and devices inside the office. Every aspect we just talked about falls under the physical area of a defense in-depth strategy – and it’s a very important one.

Threat actors don’t always use computers to attack a network or system. Sometimes, they walk into the office and tamper with things from the inside. That’s why it’s important to spend money on alarms, security cameras, and similar things that prevent intruders from walking into your company like they would at home.

3. Technical Area

Software and hardware fall under this area. It’s the aspect most people think about when they think about cybersecurity – though you now know it’s far from the only one.

You should think about the technical area as anything that helps fend off any attacks – but not as every piece of hardware and software you can find in the office. Most devices don’t fall under this category, though endpoint protection surely does.

Think about it this way: the technical area is the tools you have at your disposal to stop the threats you’ll learn about below.

5 Threats You’ll Stop With Did

1. DDoS Attacks

A single DDoS attack can leave your website offline for days on end – and there’s not much you can do unless you prepare beforehand.

Should DDoS attacks be a major concern? Everyone should have their online shields ready to deflect these cyberattacks as soon as they happen. Believe us when we tell you they may happen to you too: studies show the number of DDoS attacks has increased by 150% in one year alone.

Why are DDoS attacks increasing so much? Because hackers have an easy time hoarding zombie devices and adding them to their botnet (a key part in orchestrating these cyberattacks). The success of the IoT model is certainly to blame for that, though that’s a topic for another time.

2. Insider Threats

Insider threats are a huge concern for companies. It often comes in the shape of a disgruntled employee or former employee looking to do damage.

What’s so dangerous about an insider threat? The user-turned-threat-actor already has the keys to unlock the vault – which means they can do a lot of damage and raise little suspicion as they do.

Sometimes, insider threats happen because of company negligence: someone in the IT department forgets to revoke access to a recently-fired employee. Other times, it’s almost impossible to detect, as it often happens during corporate espionage cases.

3. Malware

We all know what malware is and how problematic it can be. That doesn’t mean everyone takes every measure and precaution to avoid a malware infection. A defense in-depth strategy takes every tip in the book, tool in the box, and trick in the game to fend off any malware infections coming your way.

The section below will show why companies should install anti-malware products – but never stop there. Other strategies, such as implementing network segmentation, often decrease the possible damage of an ongoing malware infection.

4. Negligence

Did you know one of the most successful cyberattacks requires a USB drive and a bit of luck? Plenty of malicious actors have penetrated incredibly tough defenses by simply leaving a malware-infected USB drive in a parking lot – only to see how an employee picks it up and plugs it into a company device.

That type of negligence can unleash a devastating data breach. Another common negligent act is using a company device to click on malicious links (often promising prizes or similar stuff), putting the company in jeopardy.

Threat actors often look to compromise employees this way to turn them into insider threats. It happens more often than one would want or think.

5. Social Engineering

Social engineering sounds complicated – but it all boils down to finding out user information online. Threat actors look for data tidbits sprinkled on social media and similar places to crack passwords or leverage information to perform spear phishing attempts.

It’s difficult to deal with social engineering because it often happens outside of the workplace and workspaces, though it’s not impossible.

How can your company prevent social engineering attacks? Implementing certain policies and guidelines will surely help: using our 7-part plan for a great defense in-depth implementation is a must to make that happen.

7 Parts of Defense In-depth

1. Anti-malware Software

You probably already know how important anti-malware software is. We won’t detail every piece of protection software you need to keep threat actors at bay – because you probably know them all: antiviruses, firewalls, and more.

However, it’s important to note they will be the foundation of your defense in-depth approach. We’re talking about the first wall of your fortress here: hackers will often bypass it or test it to see how it reacts, though it should be ready and waiting for the first round of attacks.

Does that mean anti-malware software is antiquated? Not at all! You won’t stop novel attacks with an antivirus – but it’ll deal with a vast number of malware infections.

2. Behavioral Analysis

Behavioral analysis is a fancy term for monitoring activity. You have to watch what employees, users, and apps are doing. Yes, you have to watch out for software activity too – because that’s how you often spot malware-infected products wreaking havoc inside your network.

Don’t worry! You don’t have to monitor everything manually. There’s software ready and waiting to help you with that. You’ll have to manually audit logs every once in a while, especially when an alarm rings – though software will take care of everything most of the time.

Monitoring for suspicious activity is the best way to deal with insider threats, novel malware, and other dangerous attacks (that are often difficult to detect).

3. Least-privilege Principle

One of the biggest issues in cybersecurity is users having too many network privileges. Sometimes, users have privileges they don’t know about or even know how to use!

Limiting user access is a must in most scenarios. That’s how you prevent users from becoming insider threats or negligently causing a data breach. For example, having users delete or create new files when they only have to read something is dangerous – so limiting their privileges is key here.

Least-principle privilege boils down to limiting user access to have them fulfill their task and nothing else. Doing so prevents employees from unwillingly hurting your security – and hackers from doing damage with stolen credentials.

4. Multi-factor Authentication

Multi-factor authentication (or MFA for short) is a must-have for everyone, from individual users to multinational companies. Enforcing a company-wide MFA policy could prevent the next data breach.

Why is enabling MFA so useful? Because it prevents threat actors from accessing your network, even if they stole privileged login credentials to do so. MFA requires users to authenticate their session before accessing the network – which they can only do through a phone or email already registered.

You shouldn’t stress too much if someone manages to get your login credentials if you have MFA enabled. However, you shouldn’t shoot yourself in the foot and share the codes you get via email during a phishing scam or similar.

5. Network Segmentation

We covered network segmentation a little while ago – though we believe it’s a good idea to stress how important this strategy is. You need to separate your network into different areas to protect your data from harm.

Imagine a house with no walls or doors inside. The bad guys can get to anywhere they want once they break the front door. The same thing happens in cybersecurity: no segmentation allows threat actors to steal anything they want once they infiltrate your system.

However, segmentation is akin to adding doors, locks, and alarms throughout your house. Sure, some employees may get locked out of several areas they shouldn’t enter – but the same thing will happen to hackers.

6. Policy Enforcement

Remember when we talked about the weakest cybersecurity link in every organization? Your employees, willingly or negligently, can cause the next data breach – but this DiD part can help you prevent that.

How can policy enforcement help your cybersecurity effort? You need to create policies and guidelines pointing the right way for every employee. We’re talking about covering the basics (such as password creation policies) and more advanced stuff (cyber defense guidelines).

However, creating these policies and guidelines isn’t enough. You need people auditing employee behavior and enforcing these ground rules whenever necessary.

7. Zero-trust Architecture

Similar to implementing the least-privilege principle, Zero-trust architecture modifies what we believe is normal conduct when it comes to connecting to a network. Simply put, it asks users to authenticate their connection – every time they connect.

Does that mean people will constantly require verification under zero-trust architecture? That’s right! It may sound tedious – but think about it this way: hackers will have to go through verification too, even if they stole valid login credentials, meaning there’s a huge chance zero-trust prevents future data breaches.

Zero-trust architecture is such a game-changer even the White House is mandating mass adoption for several federal agencies and contractors.


Defense in-depth is a cybersecurity strategy that takes several tools and elements to protect a system. Those who want to establish this security approach will have to implement multiple measures, such as the least-privilege principle and zero-trust architecture, as well as install anti-malware software and enforce other protocols. We at U.S. Cybersecurity are standing by to help your business implement a Defense in-depth strategy.

Herman McCargo

Herman is a Microsoft Certified Security Engineer and Cybersecurity Specialist. He’s been in the technology field for over 20 years and has expertise working with the most critical technology infrastructures. He has a deep understanding of cyber risks, threat mitigation and prevention, and overseeing infrastructure.