Why Firewall Needed

 

How These Criteria Affect Security Posture

Area	How Firewalls Improve It
🔗 Network Segmentation	Isolates workloads, prevents lateral spread of malware
🧱 Perimeter Defense	First line of defense against public attacks (DDoS, scans, etc.)
🔍 Traffic Inspection	Blocks malicious payloads even in encrypted traffic
🚧 Access Control	Enforces only approved ports, IPs, domains — reduces attack surface
📜 Audit & Compliance	Provides logs for SOCs, SIEMs, and regulatory audits
🆘 Breach Containment	Outbound filtering and IDPS limit attacker movement and impact

Real-World Example: Without Firewall vs With Firewall

Scenario	Without Firewall	With Azure FW Premium or FortiGate
A VM is compromised via phishing	It can connect to any IP, download malware, and exfiltrate data	Outbound traffic to unknown IPs is blocked; C2 attempts flagged via Threat Intel
Developer accidentally opens RDP to the world	VM is directly exposed to brute-force attacks	Firewall blocks unsolicited RDP unless coming from whitelisted IPs
TLS traffic hides malware	Firewall can't see malicious payloads	TLS inspection identifies malware inside HTTPS traffic

Lets check the Importance of Criteria to choose the Firewall fist,

🔎 Criterion	🛡️ Why It’s Important	🚨 Security Impact
1. Internet-Facing Workloads	Any public-facing resource is exposed to threats like DDoS, port scanning, brute-force attacks.	A firewall (Azure or NVA) adds a protective perimeter, blocking unsolicited inbound traffic and enforcing L3-L7 inspection. Without it, attackers can reach directly into your app services or VMs.
2. Outbound Traffic Filtering	Servers in Azure often talk to the internet (for updates, APIs, etc.). Left uncontrolled, they can become botnet members or leak data.	Filtering outbound traffic (FQDN/port-based) ensures only approved destinations are reachable. This helps prevent data exfiltration and command & control (C2) communications during a breach.
3. TLS/SSL Inspection	Most threats now use HTTPS to hide. Without decryption, firewalls are blind to malicious payloads.	TLS inspection decrypts traffic, allowing the firewall to inspect content for malware, phishing, or data leaks — ensuring encrypted traffic isn’t a blind spot.
4. IDPS (Intrusion Detection & Prevention)	Detects and blocks known attack signatures (e.g., SQL injection, shellcode, port scans).	Helps proactively stop known threats before they hit your application or database. Azure FW Premium uses Microsoft threat feeds, NVAs have their own vendor feeds.
5. Threat Intelligence Feeds	Updated feeds of known malicious IPs, domains, and URLs help auto-block connections.	Prevents connections to known bad actors even before payloads arrive — adding a real-time first line of defense.
6. East-West Traffic Filtering	Lateral movement is a key tactic in ransomware or internal breaches.	Filtering internal subnet-to-subnet traffic limits attacker movement. Only allowing “App subnet → DB subnet” blocks unauthorized peer-to-peer or cross-app access.
7. VPN/Hybrid Connectivity	Needed to securely connect on-prem to Azure (especially for regulated workloads).	NVAs like FortiGate support site-to-site and client VPNs, creating secure encrypted tunnels. Azure Firewall does not support VPN functions — so NVAs are a must for this use case.
8. Compliance & Audit Logging	Many industries (e.g., BFSI, Healthcare) require logging every network connection and proving access controls.	Firewalls log every decision (allow/deny), which is critical for forensic investigations, SOC monitoring, and meeting audit requirements. Azure FW Premium integrates well with Azure Sentinel.
9. Familiarity with Vendor Ecosystem	Some customers already have FortiGate or Palo Alto on-prem. Extending the same tool to Azure simplifies training, licensing, and policy management.	Ensures consistency of security posture across environments — the same IPS rules, SD-WAN configs, or firewall policies can be reused, reducing risk of misconfigurations.
10. Scalability & Maintenance	Native services (Azure Firewall) scale automatically, NVAs require manual sizing and patching.	Poorly scaled or outdated NVAs could fail under attack or load, creating a security risk. Azure Firewall avoids that with automatic scaling and updates by Microsoft.