L is for Layers
Learning the ABCs is important to understanding the English language, and the ABCs of Information Security are important for understanding the basic concepts in information (and people) protection. These ABCs are written as education for people who don’t speak information security natively and serve as good reminders for those of us already fluent in this confusing language.
TRUTH: If more people and organizations applied the basics, we’d eliminate a vast majority of breaches (and other bad things).
Here’s our progress thus far:
- “A” is for accountability
- “B” is for business
- “C” is for cybersecurity
- “D” is for data
- “E” is for everyone
- “F” is for fundamentals
- “G” is for governance
- “H” is for holistic
- “I” is for if
- “J” is for jaded
- “K” is for key
So, now the beloved letter “L”.
Lethargic Larry’s lackadaisical use of network layers, and his leisurely approach to security let lazy criminals move laterally throughout the lattice, leaving his league of lawyers lamenting the long laborious litigation laid before them from the lye leaked into the lotic.
For the purposes of the Information Security ABCs, “L” is for “Layers”.
To best apply the word “layer” with our definition of “information security”, let’s review both definitions quick. The word “layer” has several definitions in the English language, and here are two:
- a thickness of some material laid on or spread over a surface: a layer of soot on the windowsill; two layers of paint.
- something lying over or under something else; a level or tier: There can be multiple layers of metaphor in a single poem.
You remember our definition of “information security” right? Maybe. Well, in case you forgot, it’s managing risk to unauthorized disclosure, modification, and destruction of information using administrative, physical, and technical means (or controls).
So, what is an “information security layer” or “security layer” for short?
What is a Security Layer?
In the context of information security, we use the term layers to describe the controls, most often preventative controls. A single layer is less strong (or effective) than multiple layers. For multiple layers, we just stack one layer on top of another (logically) to make our security (and protection) stronger. Here’s an analogy:
- Bullet-resistant glass is constructed using multiple layers of laminated glass. The more layers there are, the more protection we get from the glass. Note, the glass is bullet “resistant” and not bullet “proof”. A projectile that is powerful enough, will get through. The point is, the layers make the protection stronger.
- Attacker-resistant networks are constructed following the same concept, but using multiple layers of network protection (segmentation and isolation, maybe provided by firewalls) instead of multiple layers of laminate glass. The more layers there are, the more protection we get from the network. Like the bullet resistant glass, attacker resistant networks are never attacker “proof”.
Multiple layers make protections stronger, they compliment and compensate for each other. Here are a couple more examples:
- The most common control for authentication is a username and password, a single layer (or often referred to as “factor”). If we add another layer to the authentication, maybe a hardware token (like YubiKey or RSA SecureID), a biometic (like Face ID), or a software token (like Google Authenticator or SMS text), we’ve significantly strengthened the control. We call this multi-factor authentication (MFA), but it’s also multiple layers.
- A building is protected by exterior controls (walls, windows, doors, etc.). A single layer of protection might be provided by the walls and a single entry door. Once an attacker breaches the door (or wall or window) and gains entry to the building interior, there would be nothing left to stop them from taking anything they wanted or assaulting anyone inside. A simple multi-layer approach might employ additional locked doors between the single exterior entry point and office spaces, between office spaces and mail rooms, between office spaces and data closets, etc., etc.
Layers are important for safety
As one who lives in a cold weather climate, I can assure you that layers are an essential part of staying safe in cold weather. As with all things, having the appropriate number of layers is critical, too many layers and you overheat and struggle to move, not enough layers and you will freeze.
When it comes to using layers in security the same principal applies, too many layers prevents effective use and not enough layers leads to unnecessary risk and danger.
Layers are part of defense in depth
We like to use the analogy that security is like an onion, we say this because an onion has many layers and each layer is needed to make a whole onion, in security it is no different. You may need many layers to make the whole security program effective.
Layers are the cornerstone of defense in depth, defense in depth is a security concept that states; security should be implemented in overlapping layers that provide the three elements needed to secure assets, prevention, detection and response, while seeking to offset the weakness of one security layer by strengthening it with two or more additional layers. This is the #1 reason for using Multi Factor Authentication (MFA) to strengthen the security of your username and password.
Let’s take a deeper look at the various security layers, we encounter most often.
The physical layer consists of the things you can touch, fences, locked doors, surveillance cameras, man in the middle traps (a room that one door locks behind you before the door in front of you can be opened) security guards, etc. This is the fist layer of any security program; all the other layers are ineffective if the systems can be physically accessed by bad actors. Having an appropriate level of physical controls in place is critical to ensuring the rest of the security layers are effective. After all,
“It doesn’t matter if your server runs the greatest security software of all time when someone steals the server.”
The access control layer comes in two forms physical access and logical access, both serve the same purpose, to limit access to sensitive systems and data to authorized personnel (approved users only). The most common physical access controls are door locks, and the most common logical access controls are passwords (used in combination with a username).
Access control gives us the ability to restrict and monitor who is accessing what, and physical and logical access controls can have many sublayers. For example a locked door could have additional layers (controls) of security such as a surveillance camera or security guard. Logical examples include multi-factor authentication (MFA) covered earlier, or performing logical access audits on a periodic basis.
The application security layer is all about providing protection to applications and the data applications use. Security controls on the application layer require additional consideration, as poorly configured security controls can degrade the performance, stability, and overall usability of an application. Inadequate or missing security controls at the application layer present significant risks, such as data loss, data integrity issues, backdoors/malware, additional unauthorized network access and service interruption.
Ransomware, Distributed Denial of Service (DDoS) attacks, SQL injection and cross site scripting are some of the attacks targeted at the application layer.
Taking a multi-layered approach to application security is a best practice. Using a Web Application Firewall (WAF) for web facing applications, secure web gateway services for Internet access, logging and monitoring of application activities and training aimed at improving user behaviors are a great starting points to consider for a multi-layered approach to application security.
The network layer is responsible for connecting systems together. Systems within an organization are likely to need communication capabilities with each other to operate, and connectivity to the Internet may also be required. This is the layer where a standard firewall lives. You know, that thing we traditionally think of when we talk about cybersecurity (BTW, cybersecurity is not information security. They’re like cousins)?
Think of the network layer as your first chance and last chance; it is your first chance to detect suspicious traffic/behaviors, and it’s your last chance to stop data from leaving your network. The network layer has two directions that must be considered in your protection approach, inbound (sometimes called “ingress”) and outbound (sometimes called “egress”). Controlling and monitoring data and traffic in both directions are critical, although this contrary to current practice in many organizations.
The Crunch Shell and Gooey Center
Most networks are secured (poorly) with a “crunchy shell” and “gooey center”. Traditionally, we’ve focused so much on establishing a strong perimeter (“crunchy shell”) that we neglect to account for what happens when an attacker get’s through the perimeter. There are few restrictions in place, and we’re left with our “gooey center”. In most networks, once an attacker gets through the perimeter (trivial in many cases), they have free reign to move laterally throughout the network until they find valuable data. Once the attacker finds valuable data, they are rarely restricted in exfiltrating the data because of ineffective egress traffic restrictions.
The two most common mistakes in network security layering include:
- Too much focus on the perimeter.
- Too much focus on restricting traffic inbound and no (or very little) focus on traffic outbound.
An important note about the “perimeter”, especially with the explosion of remote work due to COVID-19, is there is no perimeter. At the very least, there are many perimeters. All the more reason for a layered approach.
Some of the tools used to secure the network layer are firewalls, security incident and event management (SIEM) tools, network intrusion prevention systems (NIPS), network intrusion detection systems (NIDS), logging and packet capture devices, network-based data loss prevention (DLP), email filtering, and web filtering.
The better the network layer is secured and monitored the higher the your chances of seeing something in time to stop the “something” from being very bad. Some of the controls we use to secure the network layer are physical and some are logical. The best approaches are usually a blend of both. When it comes to the securing the network layer, less is more and, more is less.
Whoa, did I just blow your mind?! How can it be both more and less you might ask.
The answer is painfully simple, the more restrictive you are with what you allow on the network without the knowledge of what it does or why, the less issues you will have to chase down later. Knowing what something is, why it’s on the network, why it’s important to the business and how it works/behaves during normal operation are invaluable when it comes to securing the network layer. The better you understand what’s on the network and how it operates the better your firewall rules, IPS, IDS, WAF, log data, SIEM and other security controls can be configured. This always results in less things to chase and less time elapsed between detection and response.
Remember when it comes to network access Less is More! (concept of least privilege)
While the network layer has traditionally gotten the most attention from security professionals over the years, and is where the concept of perimeter defense is rooted, it is only one of the many layers you need to design and manage an effective information security program.
Host / Platform
The host layer is where virtualization happens and where operating systems live, virtual or not. This is also the layer that computers/servers/Internet of Things (IoT) and all other devices (with a unique IP address) reside. When we discuss this layer, in the cloud as IaaS or other, we refer to it as the platform layer and there are some distinct differences in how to secure it. Securing this layer comes with the challenge that most devices need to interact with many applications and services hosted locally and remotely. When we consider all the various other layers and systems at play, we must consider virtualization, application stacks, code libraries, 3rd party services, integrations and data movements, security patches, upgrades, cloud services and on and on.
Adding to the challenge, we must do this while balancing the needs of the business and risk.
The WORST ENEMY of security is complexity; therefore, we must combat complexity at all times. This is a huge challenge when dealing with the (sometime unreasonable) demands of the business. Using a simplified approach whenever possible, and leveraging a layered approach to information security will make your life easier and your protections more effective. Believe it or not, the fundamentals are still the most effective security controls out there.
Honorable mentions for “L”
- Laser Printer
- Lazy Loading
- Live Streaming
- Load Balancing
- Log File
- Log On
- Logic Error
- Logic Gate
- Low-Level Language
So, there it is folks. The letter “L” is for “Layers”.
The key to good information security is understanding information security for what it is (see the definition earlier in this post) and to master the basics. Mastery isn’t just knowing what the basics are (lots of “experts” know the basics), but to master them in application too (few “experts” are good at applying the basics). APPLY THE BASICS!
On to “M”!
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