What is a Security Policy in Palo Alto?

In a Palo Alto Next-Generation Firewall, a Security Policy is the core control mechanism that determines how traffic is allowed or denied between zones.
In simple terms, it answers:
WHO (Source User / IP / Zone)
WHAT (Application – App-ID)
FROM WHERE (Source Zone)
TO WHERE (Destination Zone / IP)
USING WHICH SERVICE (Port / Application-default)
WHAT ACTION (Allow / Deny / Drop / Reset)

hashtag#Important: Palo Alto follows Top-to-Bottom rule order.
First match wins.

Real-Time Practical Scenario
User PC: 10.10.X.X
Application Server: 10.20.X.X
Application: HTTPS (App-ID: ssl / web-browsing)
Zones:
Trust (User LAN)
DMZ (Application Server)

Requirement:
Allow users from the Trust zone to securely access the internal application server over HTTPS.

When Do We Configure Security Policies?
You create or modify security rules when:
✔ New server is deployed
✔ New application goes live
✔ Access requirement changes
✔ Internet access must be restricted
✔ Department segmentation is required
✔ Compliance mandates (PCI-DSS, ISO 27001)
Security policies are not just configuration — they define your organization’s security posture.

How to Configure Security Policy (GUI – Step-by-Step)
Step 1:
Policies → Security → Add
Step 2 – General Tab
Name: Allow_Trust_to_DMZ_HTTPS
Rule Type: Universal
Step 3 – Source Tab
Source Zone: Trust
Source Address: 10.10.X.X (or Address Object)
User: any (or AD Group)
Step 4 – Destination Tab
Destination Zone: DMZ
Destination Address: 10.20.X.X
Step 5 – Application Tab
Select: ssl (Best Practice)
🚫 Avoid using “any”
Step 6 – Service Tab
Select: Application-default
Step 7 – Actions Tab
Action: Allow
Enable Log at Session End ✅
Click Commit

CLI Verification Commands
show running security-policy
show session all filter source 10.10.X.X

show log traffic
🔄 How Firewall Processes Security Policy (Packet Flow)
1️⃣ Packet enters firewall
2️⃣ Zone identification
3️⃣ Session lookup
4️⃣ Security Policy lookup (Top → Bottom)
5️⃣ App-ID identification
6️⃣ Rule match
7️⃣ Content inspection (AV, IPS, URL filtering)
8️⃣ Final action applied

✅ Best Practices
✔ Keep specific rules above general rules
✔ Place explicit “Deny Any” at bottom
✔ Always use Application-default
✔ Enable logging at session end
✔ Avoid “any-any allow”
✔ Attach Security Profiles (AV, IPS, URL Filtering, Anti-Spyware)
Zero Trust starts with clean policy design.