Enterprise Firewall: Role, selection criteria and effective deployment

Hung Pham
Jan 15
8 min read

An enterprise firewall is a security system that controls traffic entering, leaving, and moving between network segments based on predefined security policies. A suitable solution does more than block unauthorized connections. It can also support intrusion detection, application control, remote access management, and log collection for incident investigation.

However, purchasing a high-performance firewall does not automatically make an organization secure. Real-world effectiveness depends on network architecture, access policies, patch management, monitoring capabilities, and how the firewall is operated after deployment.

What is an enterprise Firewall?

A firewall is a network security system that monitors and controls traffic according to predefined rules. It is commonly deployed between an internal network and the Internet, between headquarters and branch offices, or between network zones with different trust levels.

According to NIST, a firewall policy should clearly define which types of traffic are allowed to pass based on the organization’s risk assessment and operational requirements. Firewalls should also be tested, managed, and updated throughout their lifecycle rather than configured once and left unchanged.

In an enterprise environment, a firewall may perform the following functions:

Allow or block connections based on IP address, port, and protocol.
Control applications and user groups.
Detect and prevent certain intrusion attempts.
Filter websites and inappropriate content.
Establish VPN connections for employees and branch offices.
Record logs for monitoring, auditing, and incident investigation.
Segment traffic between servers, users, guests, and IoT devices.

Businesses should distinguish between a network firewall and a firewall installed on an individual computer. An operating system firewall protects a specific device, while an enterprise firewall controls traffic across multiple systems, network zones, branches, and centralized services.

For a deeper explanation of firewall technologies and generations, businesses can refer to What Is a Firewall? Types and Selection Guidance for Businesses.

What risks can an enterprise Firewall help prevent?

A firewall creates an important control layer at the network perimeter and between internal network segments. It helps protect systems from malicious or unnecessary external traffic. However, a firewall cannot prevent every type of cyberattack on its own.

firewall-for-business — *Why do businesses need to invest in a powerful firewall?*

Unauthorized access from the Internet

Businesses often need to expose certain services, such as VPN gateways, websites, email gateways, or remote administration portals. Without appropriate access controls, these services can become entry points for attackers.

A firewall helps restrict access to authorized services, trusted sources, and approved user groups.

Exploitation of exposed services

Attackers frequently scan the Internet for edge devices, VPN gateways, and services affected by known vulnerabilities. Security agencies have repeatedly warned that threat actors successfully compromise organizations by exploiting known CVEs in Internet-facing devices.

This means businesses should not treat a firewall as an unchanging black box. The firewall itself is an asset that requires firmware updates, restricted administrative access, and continuous monitoring.

A real-world example is the wave of attacks targeting more than 73,000 Fortinet firewalls, which shows that security appliances can still become targets when they contain vulnerabilities or are misconfigured.

Abuse of remote access

VPNs allow employees to access internal resources remotely, but they also expand the attack surface. Common risks include stolen accounts, weak passwords, missing multi-factor authentication, and compromised endpoint devices.

A firewall can restrict user groups, accessible resources, and connection times. However, businesses should also combine it with MFA, identity management, and session monitoring. The article Can a VPN Be Hacked? provides a more detailed analysis of these risks.

Does using a VPN make you impossible to hack? 2026 truth

Lateral movement within the internal network

Once an endpoint has been compromised, an attacker may attempt to access servers, accounting systems, shared data, or administrative accounts.

Dividing the network into separate zones and applying firewall rules between those zones can reduce lateral movement. For example, a guest network should not be able to access internal servers, and IoT devices should not connect directly to financial systems.

Businesses can combine firewall deployment with enterprise VLAN design and segmentation to control traffic between different asset groups.

Common types of enterprise Firewalls

There is no single firewall type that fits every organization. The right choice depends on infrastructure architecture, working models, security requirements, and operational capabilities.

Firewall type	Main capabilities	Best suited for
Packet-filtering firewall	Inspects IP addresses, ports, and protocols	Small networks or basic access control
Stateful firewall	Tracks the state of active connections	Businesses requiring standard network traffic control
UTM firewall	Combines firewall, VPN, IPS, web filtering, and gateway antivirus	SMEs seeking multiple security functions on one platform
Next-generation firewall	Provides application awareness, user identification, IPS, content inspection, and threat intelligence	Businesses requiring advanced visibility and control
Cloud firewall	Protects cloud workloads, cloud networks, or distributed users	Organizations using cloud, hybrid cloud, or multiple locations
Web application firewall	Protects web applications and APIs at the application layer	Websites, customer portals, e-commerce systems, and online services

A network firewall and a web application firewall do not replace each other. A network firewall controls connections between networks and infrastructure zones, while a WAF protects web applications from malicious application-layer requests.

Similarly, a next-generation firewall does not automatically replace endpoint security, email security, identity management, or a Security Operations Center. A firewall is only one component of a layered defense strategy.

6 criteria for selecting an enterprise Firewall

A common mistake is choosing a firewall based only on the number of employees or the maximum throughput advertised by the vendor.

Businesses should evaluate at least the following criteria.

1. Performance with security features enabled

Basic firewall throughput is usually much higher than actual throughput when IPS, SSL or TLS inspection, gateway antivirus, or application control is enabled.

Businesses should therefore evaluate performance under the configuration they intend to use, rather than relying only on the highest published throughput figure.

2. Number of users and concurrent connections

Two businesses with 100 employees may have completely different requirements. A company using only email and office applications will generate different traffic from one operating cameras, servers, ERP systems, IoT devices, or continuous online transactions.

Important metrics include:

Number of concurrent sessions.
New session creation rate.
Number of simultaneous VPN connections.
Traffic volume between headquarters and branch offices.
Number of VLANs and security zones.

3. Encrypted traffic inspection

A large proportion of Internet traffic is encrypted. If a firewall cannot inspect encrypted traffic where appropriate, malware and command-and-control connections may remain hidden inside HTTPS sessions.

However, SSL inspection consumes significant resources, may affect performance, and must be deployed in accordance with privacy, legal, and operational requirements.

4. Scalability

Businesses should consider future workforce growth, new branch offices, cloud migration, and the introduction of additional online services.

A device that is only sufficient for current needs may quickly become a bottleneck if it does not provide adequate performance headroom.

5. Management and logging capabilities

A firewall should provide enough logging detail to answer questions such as:

Who accessed the system?
Where did the connection originate?
Which application was used?
Which asset was accessed?
Which rule caused the traffic to be blocked?
Were there signs of scanning or exploitation?

Logs should also be stored centrally and integrated with a SOC or SIEM when broader monitoring is required.

6. Support and operational capability

A firewall must be patched, backed up, reviewed, and monitored regularly. Businesses without dedicated security staff should consider a managed service rather than purchasing a device and operating it without specialist support.

Business environment	Recommended approach
Small office with few exposed services	Centrally managed firewall or UTM
Multiple branches and frequent VPN usage	NGFW with SD-WAN and centralized management
Critical internal servers	NGFW combined with network segmentation and log monitoring
Hybrid cloud environment	Physical firewall combined with cloud firewall services
Limited cybersecurity staff	Managed Firewall 24/7
Enterprise-wide monitoring requirements	Firewall integrated with SOC or SIEM

When should a business deploy or upgrade Its Firewall?

A business should consider deploying a new firewall or upgrading an existing one when one or more of the following conditions apply:

A consumer-grade modem or router is being used as the primary security layer.
The device has reached end of support or no longer receives security patches.
IPS or SSL inspection cannot be enabled because of performance limitations.
The network becomes slow as the number of users increases.
The business opens new branches or introduces remote working.
The network includes many servers, VLANs, cameras, or IoT devices but lacks segmentation.
Logs are not centralized, or there is no visibility into policy changes.
The firewall contains too many outdated, duplicated, or ownerless rules.
The organization is moving to cloud or hybrid cloud infrastructure.
A security incident has occurred, but available logs are insufficient to identify the cause.

In addition to the device lifecycle, businesses should assess the lifecycle of firewall policies. Even a modern firewall can be ineffective if it contains overly permissive rules, shared administrator accounts, or a management interface exposed directly to the Internet.

Businesses can review potential risks in enterprise firewall systems to identify weaknesses in their current operating model.

How should an enterprise Firewall be deployed?

A firewall project should not begin with the selection of a brand or device model. A better approach is to identify assets, data flows, and business requirements first.

Step 1: Assess the Current Environment

Create an inventory of Internet connections, servers, applications, VLANs, VPNs, branch offices, cloud services, and systems exposed to the Internet.

Step 2: Classify Assets and Data Flows

Identify where critical data is stored, who needs access, and which network flows are genuinely required for business operations.

Step 3: Design Security Zones

At a minimum, separate user networks, servers, guest networks, cameras, IoT devices, and administrative systems. Avoid placing the entire environment on a flat network.

Step 4: Apply the Principle of Least Privilege

Only allow connections that have been confirmed as necessary. Each firewall rule should have a clear purpose, a responsible owner, and a review date.

Step 5: Test Before Migration

Test VPN connectivity, critical applications, branch connections, failover mechanisms, and rollback procedures before switching production traffic to the new firewall.

Step 6: Monitor and Optimize Continuously

Monitor alerts, system load, configuration changes, patches, and unused rules. A firewall should be treated as a continuously managed security service rather than a one-time hardware purchase.

Is a Firewall enough to protect the entire business?

No. A firewall mainly controls traffic at the points where it has visibility. It cannot fully address risks such as:

Employees entering passwords on phishing websites.
Computers becoming infected through USB devices or fake software.
Cloud accounts being compromised.
Internal users abusing access privileges.
Vulnerabilities in web applications.
Data being shared with incorrect permissions.
Compromised devices operating through otherwise allowed traffic.

Businesses should combine firewalls with endpoint security, email security, MFA, patch management, backups, network segmentation, and security awareness training.

Organizations that need to detect and respond to events across multiple data sources should integrate the firewall with a 24/7 SOC service. A SOC has a broader scope than a firewall because it collects and analyzes events from servers, endpoints, identity systems, cloud platforms, and other security tools.

24/7 SOC Services | Security Operation Center | IPSIP Vietnam

An enterprise firewall is a foundational security control that helps manage network traffic, restrict unauthorized access, protect remote connections, and segment critical network zones. However, its true value does not come from purchasing an expensive device. It comes from designing, configuring, and operating the firewall correctly.

Businesses should select a firewall based on actual bandwidth requirements, concurrent sessions, VPN usage, encrypted traffic inspection, cloud architecture, and monitoring needs. Firewall policies should be reviewed regularly, devices must be patched, and alerts must be investigated by responsible personnel.

For organizations without a dedicated cybersecurity team, a Managed Firewall 24/7 service can support environment assessment, configuration management, log monitoring, policy updates, and the investigation of suspicious activity.

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Frequently Asked Questions

Does a small business need a dedicated firewall?

Yes, especially if the business stores sensitive data, operates servers, uses VPNs, manages many devices, or provides online services. The appliance may be smaller, but security policies, patching, and monitoring still need to meet the actual risk level.

Can a firewall stop ransomware?

A firewall can block certain malicious connections, Internet-based exploits, and command-and-control traffic. However, ransomware can still enter through phishing, stolen accounts, or compromised endpoints. Businesses should combine firewalls with email security, endpoint protection, MFA, backups, and continuous monitoring.

How often should firewall policies be reviewed?

Firewall policies should be reviewed regularly based on how frequently the environment changes. They should also be reviewed whenever a new service is introduced, a provider changes, an application is deployed, a security incident occurs, or administrative staff changes.

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