Network Security Group - Protect Your Digital Assets

A network security group (NSG) is a protective measure for modern cloud security. It serves as a granular filter for the traffic entering and leaving your network, acting as a virtual firewall. NSGs allow your organization to regulate access to its network based on predefined rules. This flexibility and scalability help protect your data with an additional layer of security behind your main line of defense. Learn the essentials of network security groups as well as their most common features, best practices, and steps to get started.

What is a network security group?

A network security group (NSG) is a set of rules that controls incoming and outgoing traffic to and from a virtual network interface, subnet, or other network resource within a cloud environment. These rules are usually based around parameters like source and destination IP addresses, ports, and protocols.

NSGs play a very important role in cloud environments by regulating traffic and increasing security. They block unauthorized access and facilitate legitimate connections based on the rules you set. In effect, NSGs prevent a potential cybersecurity threat while restricting traffic at various network levels. For example, in Microsoft Azure, you can assign NSGs to subnets along with the individual virtual machines (VMs) within them to enforce security policies specific to each resource.

It’s important to note that an NSG can only operate on Open Systems Interconnection (OSI) layer three, the network layer, and layer four, the transport layer. This differs from a firewall, which operates on layers three, four, and seven, the application layer. Because of the additional layer offered by a firewall, some organizations opt for both an NSG and a firewall.

Key features of network security groups

NSGs offer three major advantages for your virtual network: the ability to define the security rules for network traffic, the ability to provide additional security at the network layer, and the ability to log the IP traffic passing through your NSG. Take a closer look at each of these key features:

Rule-based access control

NSGs operate using a series of rules that define whether to allow or deny certain traffic. Rules process in order of priority, starting from the lowest numbered rule. Rules can specify:

• Direction: Whether inbound or outbound, traffic should follow the rule

• Source and destination: Which IP ranges or addresses to permit

• Protocol: Whether the rule applies to TCP, UDP, ICMP, ESP, AH, or Any

• Port range: Which ports the rule affects (such as port 80 or port 10000-10005)

• Action: Whether something can or cannot occur

Security at the network layer

NSGs complement your firewall to provide additional security at the network layer. Specifically, they control traffic based on the rules set by your administrator and manage data packets based on IP and port information. This approach helps ensure the virtual network has proper protection, contributing to a more secure cloud environment.

Logging and monitoring

Logging and monitoring are essential for maintaining the security of your infrastructure and responding to threats. Features like flow logs in Azure NSGs allow administrators to analyze traffic patterns for suspicious activity, identify anomalies, and fine-tune the rules. 

Further integration with tools like Azure Monitor or AWS CloudWatch only improves the NSG's logging and monitoring capabilities.

Who uses network security groups?

From multi-cloud to hybrid-cloud setups, NSGs can be a useful tool for many organizations hoping to add an extra layer of protection. Some professionals who can benefit from NSGs include:

Cloud administrators

NSGs help cloud administrators manage the traffic patterns and security issues of cloud environments. This supervision is vital for ensuring that only authorized traffic reaches your organization’s critical resources.

Network engineers

For network engineers, NSGs simplify traffic management by offering you centralized control over access rules and configurations.

IT security professionals

Security teams rely on NSGs to enforce compliance with organizational policies, secure virtual machines, and isolate development environments.

Best practices for configuring network security groups

When setting up an NSG, you want to adhere to certain best practices in order to make it as effective as possible. While configuring your NSG, keep in mind:

Least privilege principle

Implementing the principle of least privilege (PoLP) ensures that only the necessary systems and users receive access. For example, when dealing with a third-party contractor, you want to limit the time and scope of their access to your system or limit outbound traffic to trusted domains.

Regular audits and updates

Conduct periodic reviews of your NSG configurations to identify outdated or overly permissive rules. Update these rules to reflect changes in infrastructure or policy.

Use of tags and application security groups

Tags and application security groups (ASGs) simplify rule management by grouping resources with similar security requirements. For example, you can assign rules that permit inbound traffic from certain IP addresses to a particular group of web servers.

How to get started with network security groups

To set up your first NSG, head to the Microsoft Azure portal and log into (or create) your Azure account. (This process will be different for PowerShell or Azure CLI users). Next, select “Network security groups” and click “Create.” 

From there, define your inbound and outbound security rules based on your organizational requirements. Then, assign the NSG to a subnet or network interface to associate it with the necessary resources. 

Testing your NSG configuration

Testing helps make sure your NSG rules work as intended. Some methods include: 

• Network traffic simulations: Use tools like Wireshark to analyze packet flow and simulate network traffic.

• Penetration testing: Verify the robustness of your rules against potential attacks by running penetration testing.

Learning resources

To deepen your understanding of NSGs, consider consulting the detailed guides and tutorials offered by platforms like Microsoft Azure. You can also join discussions on community forums through Stack Overflow or the Microsoft Support Community. Boot camps that cover network cybersecurity are also available. Platforms like YouTube also provide step-by-step video walkthroughs.

Learn more about network security groups on Coursera

Network security groups (NSGs) are an extra layer of cloud data security beyond the firewall, offering rule-based access control, layered protection, and monitoring capabilities to help your organization protect its digital resources.

To continue exploring NSGs, IBM offers an Information Technology (IT) and Cloud Fundamentals Specialization on Coursera, where you can learn about cloud computing, operating systems, and cyberattacks.