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7.1 Ensure application security policies exist when allowing traffic from an untrusted zone to a more trusted zone

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Information

When permitting traffic from an untrusted zone, such as the Internet or guest network, to a more trusted zone, such as a DMZ segment, create security policies specifying which specific applications are allowed.

**Enhanced Security Recommendation: ** Require specific application policies when allowing any traffic, regardless of the trust level of a zone. Do not rely solely on port permissions. This may require SSL interception, and may also not be possible in all environments.

Rationale:

To avoid unintentionally exposing systems and services, rules allowing traffic from untrusted zones to trusted zones should be as specific as possible. Application-based rules, as opposed to service/port rules, further tighten what traffic is allowed to pass. Similarly, traffic from trusted to untrusted networks should have a security policy set, with application-based rules. A 'catch-all' rule that allows all applications will also allow malware traffic. The goal should be to understand both inbound and outbound traffic, permit what is known, and block all other traffic.

Impact:

Setting application based rules on both inbound and outbound traffic ensures that the traffic on the protocol and port being specified is actually the application that you expect. For outbound traffic, the days of 'we trust our users' is well past us, that statement also implies that we trust the malware on the user workstations, which is obviously not the case.
For traffic from trusted to less trusted interfaces, the applications should be characterized over time, with the end goal being that all applications in in the rules, and a final 'block all' rule is in place. Not having this goal gives both attackers and malware the leeway they need to accomplish their goals.
Trusting only Port permissions to control traffic exposes an organization to 'tunneling' style attacks that can exfiltrate data or facilitate Command and Control (C2) sessions.

NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.

Solution

Navigate to Policies > Security.
For all Security Policies that transit from a less trusted to a more trusted interface, set the Application and Service values to match the exposed application. For instance, for a web server exposed to the internet from a DMZ:
Source tab: Zone set to OUTSIDE / Address set to Any
Destination tab: Zone set to DMZ / Address set to [DMZ Host Object]
Application tab: set to web-browsing
Service/URL Category tab: set Service to ether:

application-default
or:

service-http and/or service-https

**Enhanced Security Recommendation: **
Set these values for Policies on all Interfaces, for traffic in all directions. For each Security Policy, set the Application and Service values to match the exposed application.

Default Value:

Not Configured

See Also

https://workbench.cisecurity.org/benchmarks/9271

Item Details

References: CSCv7|14

Plugin: Palo_Alto

Control ID: 751339dc45b63c6a0819b7a10f4f4721f844358747eba5bf2f35bd28b69b4785