Firewall Review Runbook

A firewall review is not simply a search for permit any any. A professional review determines whether every allowed network path is necessary, appropriately restricted, monitored, owned, and aligned with the organization’s security architecture.

Welcome to the Firewall Review Runbook.

This runbook builds directly on:

Firewall Security Lab
VPN Security Lab
Network Threat Investigation Lab
Network Security Assessment Runbook

You will now go deeper into one of the most important network-security controls:

The enterprise firewall rulebase.

The objective is to move from:

I understand firewall rules.

to:

I can systematically review an enterprise firewall configuration, identify dangerous access paths, determine business impact, recommend remediation, and validate the resulting security posture.

🎯 Runbook Information

Item	Details
Runbook	Firewall Review Runbook
Difficulty	Intermediate → Advanced
Estimated Time	3–6 Hours
Primary Focus	Firewall Architecture, Policy & Governance Review
Target Roles	Network Security Engineer, Firewall Engineer, Security Consultant
Certification Alignment	CCNA, CCNP Security
Career Skill	Enterprise Firewall Security Assessment
Output	Firewall Review Report, Findings Register, Rule Review Matrix, Remediation Plan

🏢 Assessment Scenario

You have joined an enterprise security team as a Network Security Engineer.

The organization has accumulated hundreds of firewall rules over several years.

The rulebase contains policies created for:

applications
administrators
vendors
migrations
troubleshooting
remote access
production systems
internet-facing applications
legacy systems

Security leadership is concerned that the firewall may contain:

overly broad rules
Any/Any access
public administrative exposure
unnecessary internet access
stale rules
shadowed rules
temporary rules that were never removed
undocumented NAT
insufficient logging
rules without owners

You have been asked:

Does the firewall actually enforce least-privilege network access?

🎯 Review Objectives

By the end of this runbook, you should be able to:

understand firewall architecture
identify firewall trust boundaries
review zones and interfaces
analyze firewall rules systematically
identify Any/Any access
review source and destination scope
review services and ports
assess public exposure
review inbound publishing
review outbound access
assess inter-zone traffic
review NAT
assess management-plane security
evaluate logging
identify unused rules
identify shadowed rules
review temporary access
establish rule ownership
evaluate recertification
rate firewall findings
recommend remediation
validate firewall changes
produce professional reports

⚠️ Authorization and Change Safety

Before reviewing the firewall, confirm:

firewall devices in scope
environments in scope
production/non-production
whether configuration export is permitted
whether logs may be reviewed
whether active testing is permitted
whether changes are permitted
approved maintenance windows

A review does not automatically authorize configuration changes.

Do not remove a suspicious-looking rule simply because:

you cannot immediately determine why it exists.

First determine:

ownership
dependencies
traffic usage
business requirement
change history

🧭 Firewall Review Workflow

Use:

Scope
 ↓
Architecture
 ↓
Zones
 ↓
Interfaces
 ↓
Objects
 ↓
Rulebase
 ↓
Inbound Exposure
 ↓
Outbound Access
 ↓
Inter-Zone Access
 ↓
NAT
 ↓
Management Plane
 ↓
Logging
 ↓
Rule Usage
 ↓
Governance
 ↓
Attack Paths
 ↓
Findings
 ↓
Remediation
 ↓
Validation
 ↓
Reporting

01 — Define the Review Scope

Start by identifying:

firewall name
firewall purpose
location
business owner
technical owner
software/version
HA architecture
managed zones
internet connectivity
VPN connectivity
critical systems protected

📋 Firewall Scope Worksheet

Item	Details
Firewall Name
Location
Environment
Platform
Technical Owner
Business Owner
HA Configuration
Internet Edge	Yes / No
VPN Gateway	Yes / No
Critical Networks Protected

02 — Understand the Firewall’s Purpose

Ask:

Why does this firewall exist?

It may be:

perimeter firewall
internal segmentation firewall
data-center firewall
branch firewall
VPN firewall
cloud-edge firewall

🧠 Why This Matters

A perimeter firewall and an internal segmentation firewall have different security responsibilities.

For example:

Perimeter Firewall
Internet
   ↓
Enterprise

while:

Internal Firewall
Users
  ↓
Applications
  ↓
Databases

protects internal trust boundaries.

03 — Review High Availability

Determine whether the firewall operates as:

Active / Standby

or another supported resilient architecture.

Review:

peer health
configuration synchronization
failover status
monitoring

🧠 Operational Security

A secure firewall that becomes unavailable can still create significant business risk.

04 — Build the Firewall Architecture Diagram

Create:

                         Internet
                            |
                         OUTSIDE
                            |
                      +-----------+
                      | Firewall  |
                      +-----------+
                       /    |    \
                      /     |     \
                    DMZ   INSIDE  MGMT
                     |       |
                    Web    Applications
                              |
                           Database

Add:

VPN connections
partner connections
branches
cloud connections

where applicable.

05 — Inventory Firewall Interfaces

Create:

Interface	Zone	IP/Subnet	Purpose	Trust

06 — Review Security Zones

Typical zones may include:

OUTSIDE
DMZ
USERS
APPLICATION
DATABASE
MANAGEMENT
VPN
PARTNER
GUEST

🧠 Zone Review Question

For each zone ask:

What level of trust does this zone represent?

Which other zones should it legitimately communicate with?

07 — Build the Zone Communication Matrix

Create:

Source Zone	Destination Zone	Expected Access
Internet	DMZ	Public Services Only
Internet	Database	Deny
Users	Applications	Required Services
Users	Database	Normally Deny
Management	Infrastructure	Controlled Admin
Guest	Internal	Deny
VPN	Internal	Role Based

08 — Review Zone Design

Look for:

too many systems in one zone
mixed trust levels
management systems mixed with users
internet-facing systems inside trusted networks
databases in general server zones

🚨 Example Risk

Public Web Server
+
Internal Application
+
Database
=
Same Security Zone

This reduces the firewall’s ability to enforce segmentation between them.

09 — Inventory Firewall Objects

Review:

host objects
network objects
address groups
service objects
service groups

📋 Object Review

Object	Type	Value	Used?	Owner

10 — Review Object Naming

Prefer meaningful names such as:

HOST-PROD-WEB01

NET-PROD-DB

NET-MANAGEMENT

SVC-HTTPS

rather than:

OBJ-123

SERVER-NEW

TEMP1

🧠 Why Naming Matters

Good naming improves:

troubleshooting
security reviews
change management
incident response

11 — Identify Duplicate Objects

Look for:

WEB-SERVER
10.10.20.10

WEB01
10.10.20.10

PROD-WEB
10.10.20.10

Duplicate objects create confusion and rulebase complexity.

12 — Review Object Groups

Check whether groups contain:

obsolete systems
excessive networks
unexpected members

🚨 Important

A firewall rule may appear restrictive:

Source:
APP-SERVERS

but the object group may contain:

APP-SERVERS
├── APP01
├── APP02
├── TEST01
├── OLD-SERVER
└── ENTIRE-SUBNET

Always review the objects behind important rules.

13 — Export the Firewall Rulebase

Collect where authorized:

rule ID
rule name
source zone
source
destination zone
destination
service
action
logging
comments
hit count
owner
last modified

📋 Master Rule Review Matrix

Rule	Source	Destination	Service	Action	Logging	Owner	Required?

14 — Review Rules Top to Bottom

Understand how the firewall evaluates policy.

Conceptually:

Traffic
  ↓
Rule 1
  ↓
Rule 2
  ↓
Rule 3
  ↓
Matching Rule
  ↓
Action

🧠 Rule-Order Principle

A correct rule in the wrong position can still produce incorrect security behavior.

15 — Identify Any/Any Rules

Search for patterns equivalent to:

Source:
ANY

Destination:
ANY

Service:
ANY

Action:
ALLOW

🚨 Do Not Automatically Delete Them

First determine:

hit count
applications using the rule
source networks
destination networks
business owner
replacement strategy

🚨 Finding Example

Finding ID:
FW-001

Title:
Unrestricted Any-to-Any Firewall Policy

Severity:
Critical

Observation:
The firewall contains a policy permitting unrestricted communication across significant network boundaries.

Risk:
The rule may bypass intended segmentation and provide extensive network reachability following compromise of a connected system.

Recommendation:
Identify legitimate traffic using the rule and replace it with specific source, destination, and service-based policies before removing the broad rule.

16 — Review Any-Source Rules

Example:

Source:
ANY

Destination:
APP-SRV01

Service:
HTTPS

Ask:

Does the application truly need to be reachable from every source zone?

17 — Review Any-Destination Rules

Example:

Source:
APP-SRV01

Destination:
ANY

Service:
HTTPS

Ask:

Does this server genuinely require HTTPS access to every destination?

18 — Review Any-Service Rules

Example:

Source:
Users

Destination:
Application

Service:
ANY

Ask:

Which application services are actually required?

🧠 Rule Review Formula

For every rule:

WHO
 ↓
CAN ACCESS WHAT
 ↓
USING WHICH SERVICE
 ↓
FROM WHICH TRUST ZONE
 ↓
WHY?

19 — Review User-to-Server Access

Look for:

User Networks
     ↓
Server Networks
     ↓
ANY

Determine actual requirements.

20 — Review User-to-Database Access

Normally scrutinize:

Users
 ↓
Database

especially database services.

🚨 Example Finding

Finding ID:
FW-002

Title:
General User Network Can Directly Access Database Services

Severity:
High

Observation:
User endpoints can directly communicate with production database services.

Risk:
A compromised user endpoint may directly target sensitive database systems.

Recommendation:
Restrict database connectivity to approved application and management sources.

21 — Review User-to-Management Access

Check whether user networks can access:

SSH
RDP
HTTPS management
SNMP management
network-device administration

🧠 Preferred Architecture

Users
  X
Management

Management Network
      ↓
Infrastructure

22 — Review Server-to-Server Access

Do not assume server traffic is automatically trusted.

Ask:

Does this application server need to communicate with every other server?

23 — Review Application-to-Database Access

Prefer:

Specific Application
      ↓
Specific Database
      ↓
Required DB Port

over:

Application Network
      ↓
Database Network
      ↓
ANY

24 — Review DMZ-to-Internal Access

Internet-facing workloads should have narrowly defined internal access.

🚨 Weak Design

DMZ
 ↓
Internal Network
 ↓
ANY

🛡️ Better Design

WEB-SRV01
   ↓
Required App Port
   ↓
APP-SRV01

25 — Review Guest Access

Confirm:

Guest
  X
Corporate Internal Networks

unless a documented requirement exists.

26 — Review Partner Connectivity

Partner networks should be treated as:

external trust relationships.

Review:

source networks
destinations
services
ownership
expiry where appropriate

27 — Review Internet Inbound Rules

Inventory every publicly reachable service.

Create:

Public Service	Destination	Port	Owner	Required?

28 — Review Public Web Services

For public applications, validate:

Internet
   ↓
HTTPS
   ↓
Approved Web Service

and ensure unnecessary services are not exposed.

29 — Review Public SSH

Look for:

Internet
   ↓
TCP/22
   ↓
Server

Determine whether the exposure is necessary.

30 — Review Public RDP

Look for:

Internet
   ↓
TCP/3389
   ↓
Windows Server

This should receive significant scrutiny.

31 — Review Public Database Services

Look for exposure of database services.

Examples may include:

SQL Server
MySQL
PostgreSQL
Oracle database listeners

🚨 High-Risk Pattern

Internet
   ↓
Database Service
   ↓
Production Database

32 — Review Public Management Interfaces

Assess exposure of:

firewall management
router management
switch management
hypervisor management
administrative portals

🚨 Example Finding

Finding ID:
FW-003

Title:
Privileged Management Interface Exposed to Untrusted Network

Severity:
Critical / High

Observation:
A privileged infrastructure-management interface is reachable from an untrusted network.

Risk:
Attackers can directly target authentication and vulnerabilities associated with the management service.

Recommendation:
Restrict management access to approved management networks or controlled administrative-access mechanisms.

33 — Review Source Restrictions for Public Services

Ask:

Does this service need the entire internet as a source?

For public websites:

possibly.

For vendor administration:

probably not.

34 — Review Destination NAT / Publishing

Map:

Public IP
   ↓
NAT
   ↓
Internal Destination

Create:

Public IP	Private IP	Service	Business Purpose

35 — Compare NAT With Firewall Policy

Ensure that published services align with actual firewall rules.

🧠 Important

A NAT configuration may expose an address mapping, but access control still needs to be reviewed separately.

36 — Review Unused Public NAT

Identify NAT entries for:

retired systems
old projects
previous vendors
decommissioned services

37 — Review Outbound Internet Access

Create:

Source Zone	Destination	Service	Requirement
Users	Internet	Web	Yes
App	Internet	Approved API	Maybe
Database	Internet	Any	Review
Management	Internet	Any	Review

38 — Review Server Egress

Ask:

Why does this server require internet access?

🧠 Better Question

Not:

Should servers access the internet?

Instead:

Which destinations and services does this specific workload require?

39 — Review Database Egress

Scrutinize:

Database
   ↓
ANY
   ↓
Internet

🚨 Why This Matters

Unrestricted egress may increase:

command-and-control opportunities
data-exfiltration paths
malicious payload retrieval

40 — Review Management-Network Egress

Privileged management systems should not necessarily have unrestricted outbound access.

Determine actual requirements.

41 — Review DNS Egress

Determine whether endpoints can use:

ANY DNS Resolver

or whether DNS is directed through approved infrastructure.

42 — Review High-Risk Outbound Services

Investigate unnecessary outbound access using:

SSH
SMB
RDP
database protocols
unusual high ports

43 — Build an Egress Matrix

Source	Destination	Service	Required?	Recommendation

44 — Review VPN-to-Internal Rules

VPN connectivity should not automatically mean:

VPN
 ↓
ANY

45 — Review Employee VPN Rules

Prefer:

VPN-EMPLOYEES
      ↓
Approved Business Apps

46 — Review Administrator VPN Rules

Administrative access may require:

VPN-ADMINS
      ↓
Management Systems

but should be separately controlled.

47 — Review Vendor VPN Rules

Create:

Vendor	Destination	Service	Owner	Expiry

🚨 Vendor Review Question

Ask:

Does this vendor still require access?

48 — Review Site-to-Site VPN Rules

A VPN tunnel may connect:

Branch
 ↓
Head Office

but firewall policy should still restrict unnecessary traffic.

49 — Review Inter-Zone Rules

Build:

Source Zone	Destination Zone	Rules	Risk
Users	Applications
Users	Database
DMZ	Internal
VPN	Internal
Guest	Internal

50 — Review Implicit / Default Deny

Understand the platform’s default behavior.

Confirm whether traffic without a matching allow rule is denied as expected.

51 — Review Explicit Deny Rules

Explicit deny rules may provide:

policy clarity
useful logging

depending on architecture.

Review their purpose and placement.

52 — Review Rule Logging

For important rules determine:

Logging Enabled?
      ↓
At Session Start?
      ↓
At Session End?
      ↓
Forwarded Centrally?

53 — Review High-Risk Allow Logging

Consider logging important access such as:

internet inbound
privileged management
VPN-to-sensitive systems
partner connectivity

54 — Review Deny Logging

Determine whether useful deny events are available for:

investigations
threat detection
troubleshooting

🧠 Logging Balance

Too little logging creates:

visibility gaps.

Too much unplanned logging creates:

noise.

55 — Review Log Content

Confirm useful fields such as:

timestamp
source IP
destination IP
source zone
destination zone
service
action
rule name

56 — Review Central Log Forwarding

Determine whether firewall logs reach:

central syslog
SIEM
security monitoring platform

57 — Review Log Retention

Ask:

If an incident began 60 days ago, would firewall evidence still exist?

Retention should align with:

security requirements
operational needs
applicable compliance requirements

58 — Review Firewall Administration

Determine who can administer the firewall.

Create:

Administrator	Role	Source	MFA	Required?

59 — Review Management Sources

Preferred:

Approved Admin
      ↓
Management Network
      ↓
Firewall Management

60 — Review Management Protocols

Review use of:

HTTPS
SSH
secure API access

and identify insecure legacy protocols.

61 — Review Administrator Authentication

Assess:

individual accounts
centralized AAA
MFA where available
role-based administration

62 — Review Shared Administrator Accounts

Ask:

Can firewall changes be attributed to a specific person?

Shared credentials weaken accountability.

63 — Review Administrative Privilege

Not every administrator requires:

full firewall control.

Review:

read-only
operator
policy administrator
full administrator

where supported.

64 — Review Configuration Change Logging

Determine whether you can answer:

Who changed the firewall?
What changed?
When?
Why?

65 — Review Emergency Access

Identify:

break-glass accounts
emergency credentials
storage
monitoring
periodic testing

66 — Review Configuration Backups

Confirm:

backup frequency
backup protection
restore testing
version history

67 — Review Unused Rules

Where hit-count information exists, identify rules with:

0 Hits

or little recent use.

⚠️ Important

Zero hits do not automatically mean:

safe to delete.

Consider:

seasonal applications
disaster-recovery traffic
monthly jobs
rarely used administrative access

68 — Review Rule Age

Identify rules created years ago.

Ask:

does the system still exist?
does the owner still exist?
is the business requirement current?

69 — Review Disabled Rules

Disabled rules should also be reviewed.

Do they need to remain?

Or are they configuration clutter?

70 — Review Shadowed Rules

Example:

Rule 10
Users → Servers → ANY → ALLOW

Rule 20
Users → Database → SQL → DENY

Rule 20 may never be reached.

🧠 Shadowing Risk

Shadowed rules may create:

ineffective security controls
misleading configurations
troubleshooting confusion

71 — Review Redundant Rules

Example:

Rule 10
APP01 → DB01 → 443 → ALLOW

Rule 20
APP-NET → DB-NET → ANY → ALLOW

Rule 10 may provide no meaningful restriction because Rule 20 is broader.

72 — Review Duplicate Rules

Duplicate rules increase:

complexity
operational overhead
review effort

73 — Review Temporary Rules

Search names/comments for:

TEMP
TEST
MIGRATION
VENDOR
TROUBLESHOOT
EMERGENCY

74 — Validate Temporary Rule Expiry

Create:

Rule	Owner	Purpose	Created	Expiry	Required?

🚨 Example Finding

Finding ID:
FW-004

Title:
Temporary Firewall Access Remains Active Beyond Required Period

Severity:
Medium

Observation:
A firewall policy created for temporary operational access remains active without documented expiration.

Risk:
Unnecessary connectivity increases attack surface and may create an undocumented attack path.

Recommendation:
Validate the current requirement, remove obsolete access, and implement mandatory expiration for temporary firewall policies.

75 — Review Rule Comments

Important rules should explain:

business purpose
owner
ticket/change reference

76 — Review Rule Ownership

Create:

Rule	Business Owner	Technical Owner	Last Review

🧠 Ownership Question

Ask:

Who can confirm that this rule is still required?

77 — Review Rule Recertification

Determine whether firewall policies are periodically reviewed.

A mature process should evaluate:

Still Required?
      ↓
Still Correct?
      ↓
Still Least Privilege?
      ↓
Still Owned?

78 — Review Change Management

Firewall changes should generally follow:

Request
 ↓
Business Justification
 ↓
Security Review
 ↓
Approval
 ↓
Implementation
 ↓
Testing
 ↓
Documentation

79 — Review Emergency Changes

Check whether emergency changes receive:

retrospective review.

80 — Review Rule Naming Standards

Prefer:

ALLOW-PROD-WEB-TO-APP-HTTPS

over:

RULE-445

81 — Review Application Dependencies

For broad rules, determine actual flows.

Example:

APP-NET
  ↓
DB-NET
  ↓
ANY

may actually require only:

APP01
 ↓
DB01
 ↓
TCP/5432

82 — Create the Rule Optimization Plan

Use:

Broad Rule
   ↓
Analyze Usage
   ↓
Identify Required Flows
   ↓
Create Specific Rules
   ↓
Test
   ↓
Monitor
   ↓
Remove Broad Rule

⚠️ Production Tip

Do not replace a heavily used broad rule with multiple narrow rules in one uncontrolled step.

Plan:

dependencies
rollback
monitoring
change window

83 — Review Firewall Rule Hit Counts

Hit counts can help identify:

heavily used rules
potentially unused rules
unexpected rule usage

🧠 Important

Hit count answers:

Is the rule matching traffic?

It does not answer:

Is the traffic legitimate?

84 — Analyze Unexpected Rule Usage

Suppose:

Vendor Rule
Expected:
Occasional use

Actual:
Thousands of connections daily

Investigate.

85 — Build an Attack-Path View

Do not review rules only as rows.

Translate them into attack paths.

Example:

Internet
   ↓
Public Web
   ↓
ANY
   ↓
Internal Applications
   ↓
Database

🧠 Critical Question

Ask:

If the first system is compromised, which firewall rules help the attacker reach the next system?

86 — Review Internet-to-Internal Attack Paths

Map:

Internet
   ↓
Exposed Service
   ↓
DMZ
   ↓
Internal Access

87 — Review User-to-Critical-System Paths

Map:

User Endpoint
      ↓
Firewall
      ↓
Critical Server

Ask whether the path is necessary.

88 — Review VPN Attack Paths

Map:

Remote Identity
      ↓
VPN
      ↓
Firewall
      ↓
Internal Networks

89 — Review Partner Attack Paths

Map:

Partner Network
      ↓
Firewall
      ↓
Enterprise Resource

Treat partner compromise as a realistic scenario.

90 — Review Management Attack Paths

Map:

User Network
      ↓
Firewall
      ↓
Management Interface

This should generally be restricted.

91 — Build a Firewall Exposure Matrix

Source	Destination	Service	Trust Boundary	Risk

92 — Build the Findings Register

Use:

ID	Finding	Severity	Owner	Status

93 — Standard Firewall Finding Format

Finding ID:

Title:

Severity:

Affected Firewall:

Affected Rule:

Source:

Destination:

Service:

Observation:

Evidence:

Attack Path:

Risk:

Business Impact:

Recommendation:

Validation Method:

94 — Finding: Broad Internal Access

Finding ID:
FW-005

Title:
Broad Inter-Zone Access Weakens Internal Segmentation

Severity:
High

Observation:
A firewall rule permits broad communication from general user networks to multiple server networks.

Risk:
Compromise of a user endpoint may provide an attacker with extensive lateral network reachability.

Recommendation:
Identify required application flows and replace broad network access with least-privilege source, destination, and service policies.

95 — Finding: Unrestricted Database Egress

Finding ID:
FW-006

Title:
Production Database Network Has Unrestricted Internet Access

Severity:
High

Observation:
Database systems can initiate connections to arbitrary internet destinations using broad service access.

Risk:
Compromise of a database workload could provide outbound command-and-control or data-exfiltration paths.

Recommendation:
Identify legitimate external dependencies and restrict database egress accordingly.

96 — Finding: Firewall Logs Not Centralized

Finding ID:
FW-007

Title:
Firewall Security Logs Are Not Forwarded to Central Monitoring

Severity:
High

Observation:
Firewall activity is retained locally but is not consistently available to centralized security monitoring.

Risk:
Suspicious network activity may not be detected promptly, and historical evidence may be unavailable during investigations.

Recommendation:
Forward required firewall security and administrative logs to centralized monitoring and validate retention.

97 — Risk Rating Method

Use:

Source Trust
+
Destination Criticality
+
Service Exposure
+
Rule Breadth
+
Exploitability
+
Business Impact
=
Risk

🔴 Critical

Examples:

unrestricted internet-to-critical-system access
public privileged management
Any/Any bypass across critical trust boundaries

🟠 High

Examples:

broad user-to-server access
DMZ-to-database access
excessive VPN access
unrestricted critical-server egress

🟡 Medium

Examples:

stale temporary rules
unused access
rule ownership gaps
incomplete logging

🔵 Low

Examples:

naming inconsistencies
duplicate objects
minor documentation gaps

98 — Prioritize Remediation

Use:

Public Attack Paths
      ↓
Privileged Exposure
      ↓
Critical Asset Exposure
      ↓
Segmentation Weaknesses
      ↓
VPN / Partner Access
      ↓
Egress Risk
      ↓
Monitoring Gaps
      ↓
Rule Cleanup

99 — Identify Immediate Actions

Examples:

restrict public administrative access
disable confirmed obsolete vendor access
contain dangerous Any/Any paths
restrict unauthorized database access
enable critical logging

100 — Identify Short-Term Improvements

Examples:

replace broad inter-zone rules
restrict VPN groups
restrict server egress
clean stale NAT
improve management access

101 — Identify Strategic Improvements

Examples:

redesign firewall zones
introduce internal segmentation
implement centralized rule governance
automate rule recertification
improve network-security monitoring

📅 Remediation Roadmap

Timeframe	Focus
Immediate	Critical exposure
0–30 Days	High-risk rule reduction
30–90 Days	Rule cleanup and governance
90+ Days	Architectural improvements

102 — Validate Firewall Changes

Never close a firewall finding based only on:

Rule changed.

Validate actual traffic.

🧪 Positive Validation

Confirm:

Required Traffic
      ↓
ALLOW

🧪 Negative Validation

Confirm:

Unauthorized Traffic
      ↓
DENY

🧠 Security Testing Principle

A firewall change is not validated until you test both:

what should work

and:

what should not work.

103 — Validate Rule Replacement

Suppose:

Users → Servers → ANY

was replaced.

Test:

Users → App HTTPS
ALLOW

Users → Database
DENY

Users → Management
DENY

104 — Validate Public Exposure

After removing unnecessary public access:

verify required public service works
verify removed service is inaccessible

105 — Validate VPN Access

Confirm:

Employee VPN
   ↓
Business App
ALLOW

and:

Employee VPN
   ↓
Database
DENY

where that matches policy.

106 — Validate Logging

Generate controlled traffic.

Confirm the log contains:

source
destination
service
action
rule
timestamp

107 — Validate Management Access

Confirm:

Management Network
      ↓
Firewall Admin
      ↓
ALLOW

and:

User Network
      ↓
Firewall Admin
      ↓
DENY

108 — Prepare the Executive Summary

A useful executive summary should explain:

overall firewall posture
highest-risk exposures
potential business impact
immediate priorities
strategic recommendations

📄 Example Executive Summary

The firewall security review identified several opportunities to strengthen network segmentation and reduce unnecessary attack paths.

The highest-risk issues involve broad inter-zone connectivity, excessive remote-access permissions, unrestricted outbound connectivity from sensitive systems, and insufficient control over privileged management access.

Several temporary and legacy rules also require ownership validation and recertification.

Immediate remediation should prioritize externally exposed and privileged access paths.

Longer-term improvements should focus on least-privilege rule design, stronger segmentation, centralized firewall governance, periodic recertification, and improved security monitoring.

109 — Prepare the Technical Report

Recommended structure:

1. Executive Summary
2. Scope
3. Firewall Architecture
4. Zones & Interfaces
5. Object Review
6. Rulebase Assessment
7. Internet Exposure
8. Internal Segmentation
9. Outbound Access
10. VPN / Partner Connectivity
11. NAT Review
12. Management Security
13. Logging & Monitoring
14. Rule Hygiene
15. Governance
16. Findings
17. Risk Summary
18. Remediation Roadmap
19. Positive Observations
20. Validation Plan

🌟 Positive Observations

Also identify good controls.

Examples:

strong DMZ isolation
dedicated management network
narrow database rules
VPN MFA
centralized firewall logging
strong naming standards
periodic recertification
effective change management

🧠 Why Include Positive Observations?

A professional security assessment should explain:

what is working

as well as:

what requires improvement.

110 — Build the Firewall Review Checklist

Control	Status	Evidence	Recommendation
Architecture documented
Zones reviewed
Interfaces reviewed
Objects reviewed
Any/Any rules reviewed
Public exposure reviewed
Public admin access reviewed
DMZ access reviewed
User-to-server access reviewed
Database access reviewed
Egress reviewed
VPN access reviewed
Partner access reviewed
NAT reviewed
Management access reviewed
Logging reviewed
Central forwarding reviewed
Unused rules reviewed
Shadowed rules reviewed
Temporary rules reviewed
Rule ownership reviewed
Recertification reviewed
Findings risk-rated
Remediation validated

🎤 Firewall Review Interview Questions

Practise answering these without notes.

1. How would you perform a firewall security review?

2. What information would you collect first?

3. What is a firewall security zone?

4. Why is an Any/Any rule risky?

5. Would you immediately remove an Any/Any rule?

6. How would you safely replace a broad firewall rule?

7. What is a shadowed firewall rule?

8. What is a redundant firewall rule?

9. How would you identify stale firewall rules?

10. What are firewall hit counts?

11. Does zero hit count mean a rule can be deleted?

12. How would you review internet-facing rules?

13. How would you assess DMZ-to-internal access?

14. Why should database egress be reviewed?

15. Why is firewall logging important?

16. Which firewall events should be centralized?

17. How would you secure firewall management access?

18. How would you assess vendor firewall access?

19. Why should temporary rules have expiration dates?

20. How would you validate firewall remediation?

🚨 Scenario Interview Question 1

You discover permit any any on a production firewall. What do you do?

A strong answer:

Identify Rule
   ↓
Review Position
   ↓
Review Hit Count
   ↓
Identify Traffic
   ↓
Find Business Owners
   ↓
Map Dependencies
   ↓
Create Specific Rules
   ↓
Test
   ↓
Remove Broad Rule
   ↓
Monitor

Do not simply say:

Delete it.

🚨 Scenario Interview Question 2

A rule has zero hits for six months.

Investigate:

application lifecycle
disaster-recovery use
seasonal processes
owner
change records

Then determine whether removal is appropriate.

🚨 Scenario Interview Question 3

Users can connect directly to production databases.

Discuss:

User Endpoint
      ↓
Firewall
      ↓
Database

Then review:

business requirement
required application architecture
source scope
service scope
segmentation
logging

🚨 Scenario Interview Question 4

A public web server can communicate with every internal server.

Discuss:

Internet
   ↓
Web Compromise
   ↓
Broad Internal Access
   ↓
Lateral Movement

Recommend restricting the web server to required backend services.

🚨 Scenario Interview Question 5

A vendor rule has been active for three years.

Review:

business owner
vendor relationship
destination
service
usage
expiry
authentication
logging

🚨 Scenario Interview Question 6

A database server has unrestricted outbound internet access.

Ask:

what dependencies exist?
which destinations are required?
which protocols?
can access be narrowed?

🚨 Scenario Interview Question 7

The firewall logs every deny and the SOC receives millions of alerts.

Do not answer:

Disable logging.

Discuss:

event value
aggregation
detection logic
tuning
high-risk zones
alert thresholds

🚨 Scenario Interview Question 8

A firewall rule was removed and a critical application stopped working.

A strong response:

Incident
 ↓
Identify Failed Flow
 ↓
Source / Destination / Service
 ↓
Review Removed Rule
 ↓
Validate Dependency
 ↓
Restore Safely if Required
 ↓
Create Narrow Rule
 ↓
Test
 ↓
Document

🚨 Scenario Interview Question 9

A firewall rule appears secure, but its source object group contains an entire /16.

This demonstrates why you must inspect:

objects behind the rule.

🚨 Scenario Interview Question 10

Management asks whether the firewall is secure.

Do not answer with:

Yes, there are no Any/Any rules.

A stronger answer considers:

Architecture
+
Exposure
+
Segmentation
+
Rule Scope
+
NAT
+
Remote Access
+
Management Security
+
Logging
+
Governance
+
Attack Paths

🧠 Firewall Review Interview Framework

Use:

Scope
 ↓
Architecture
 ↓
Zones
 ↓
Objects
 ↓
Rules
 ↓
Exposure
 ↓
Segmentation
 ↓
NAT
 ↓
Management
 ↓
Logging
 ↓
Governance
 ↓
Attack Paths
 ↓
Risk
 ↓
Remediation
 ↓
Validation

💬 Interview Tip

Avoid:

“I check the firewall for open ports and Any/Any rules.”

A stronger answer is:

“I first understand the firewall’s role, architecture, zones, interfaces, and protected assets. I then review objects and policies for source, destination, service, rule order, public exposure, inter-zone access, egress, VPN and partner connectivity, NAT, management security, and logging. I correlate rule usage with business requirements, identify attack paths, validate ownership and lifecycle, risk-rate findings, and test both permitted and prohibited traffic after remediation.”

That demonstrates Firewall Engineer and Security Consultant thinking.

📁 Portfolio Deliverables

After completing this runbook, create a sanitized portfolio package containing:

1. Firewall Architecture Diagram

Internet
   ↓
Firewall
   ├── DMZ
   ├── Users
   ├── Applications
   ├── Database
   ├── VPN
   └── Management

2. Zone Matrix

Document expected communication between trust zones.

3. Firewall Rule Review Matrix

Include:

rule
source
destination
service
action
owner
requirement

4. Public Exposure Matrix

Document all internet-facing services.

5. Egress Matrix

Document sensitive outbound access.

6. NAT Matrix

Map:

Public Address
      ↓
Translation
      ↓
Private Resource

7. Management Access Matrix

Document privileged access paths.

8. Rule Hygiene Report

Include:

unused rules
shadowed rules
duplicate rules
temporary rules
obsolete objects

9. Findings Register

Create at least 5 professional findings.

10. Remediation Roadmap

Categorize:

Immediate
Short Term
Medium Term
Strategic

📝 Resume Examples

Instead of:

Knowledge of firewall reviews.

Use:

Performed structured firewall-security assessments covering security zones, policy rules, internet exposure, internal segmentation, egress, NAT, VPN connectivity, management access, logging, and rule governance.

Or:

Reviewed firewall rulebases for Any/Any access, stale and shadowed policies, excessive inter-zone connectivity, public administrative exposure, unrestricted server egress, and temporary access.

Or:

Developed risk-rated firewall findings and least-privilege remediation plans while validating required and prohibited traffic following policy changes.

⭐ Runbook Readiness Check

After completing this runbook, you should be able to:

understand firewall architecture
identify trust zones
review interfaces
analyze firewall objects
review firewall rules systematically
identify Any/Any access
assess source/destination scope
assess service scope
identify public exposure
review DMZ connectivity
assess user-to-server access
assess database access
review egress
review VPN rules
assess partner connectivity
review NAT
secure firewall management
assess firewall logging
identify unused rules
identify shadowed rules
identify redundant rules
review temporary access
assess rule ownership
evaluate recertification
create attack-path maps
risk-rate findings
build remediation plans
validate remediation
explain firewall risks during interviews

If your firewall review still means:

Search for Any/Any and unused rules

repeat the architecture, attack-path, and business-requirement sections.

A professional firewall review asks:

Which communication paths exist, why do they exist, what happens if the source is compromised, which critical assets become reachable, and how can we reduce that access without breaking the business?

🏆 Runbook Complete

You have now progressed through:

Firewall Architecture
       ↓
Trust Zones
       ↓
Objects
       ↓
Rulebase Analysis
       ↓
Public Exposure
       ↓
Internal Segmentation
       ↓
Outbound Security
       ↓
VPN / Partner Access
       ↓
NAT
       ↓
Management Security
       ↓
Logging
       ↓
Rule Governance
       ↓
Attack-Path Analysis
       ↓
Risk Assessment
       ↓
Remediation
       ↓
Validation

You are no longer simply reviewing firewall configurations.

You are evaluating whether the firewall is actually reducing enterprise attack paths.

🚀 What’s Next?

You have now reviewed the firewall from architecture, policy, operational, and governance perspectives.

The next runbook focuses specifically on secure administrative access to enterprise network infrastructure.

➡️ Next: Network Device Hardening Runbook

In the next runbook, you will systematically assess:

routers and switches
management-plane security
administrative accounts
AAA
privileged access
SSH
HTTPS management
Telnet and insecure protocols
SNMP security
management VLANs
access-control restrictions
console access
banners
NTP
syslog
configuration backups
unused services
software and patch lifecycle
secure configuration baselines
findings and risk rating
remediation validation
network-hardening interview scenarios