Junos Intrusion Detection and Prevention: A Closer Look

Intrusion Detection and Prevention (IDP) is a critical component of any network security strategy. In this blog post, we will delve into the IDP capabilities of Juniper Networks' Junos operating system, a key topic for those studying for the JNCIS-ENT certification.

What is IDP?

Intrusion Detection and Prevention systems are designed to identify and mitigate threats to a network. These threats can include anything from unauthorized access attempts to malware infections. IDP systems work by monitoring network traffic for suspicious activity and then taking action to prevent any potential threats.

Junos IDP

Junos, the operating system that powers Juniper Networks' devices, has robust IDP capabilities. These capabilities are built around the concept of security policies, which define how the system should respond to different types of threats.

Configuring IDP on Junos

To configure IDP on a Junos device, you first need to define a security policy. This policy specifies the actions that the device should take when it detects a threat. Here's an example of how to create a security policy:

set security idp idp-policy my-policy rulebase-ips rule 1 match attacks predefined-attacks "HTTP:STC:ACTIVEX:MS04-028-EXP"
set security idp idp-policy my-policy rulebase-ips rule 1 then action close-client-and-server
set security idp idp-policy my-policy rulebase-ips rule 1 then notification log-attacks

In this example, the policy my-policy is configured to match a specific predefined attack (HTTP:STC:ACTIVEX:MS04-028-EXP). When this attack is detected, the action close-client-and-server is taken, which terminates the connection between the client and the server. The log-attacks notification is also set, which logs the attack for later analysis.

Applying the IDP Policy

Once the IDP policy is defined, it needs to be applied to a specific interface or zone. Here's how to apply the policy to an interface:

set security policies from-zone untrust to-zone trust policy untrust-to-trust match source-address any destination-address any application any
set security policies from-zone untrust to-zone trust policy untrust-to-trust then permit application-services idp-policy my-policy

In this example, the policy untrust-to-trust is applied from the untrust zone to the trust zone. The policy matches any source address, destination address, and application, and permits traffic with the application of the my-policy IDP policy.


Junos IDP is a powerful tool for securing your network. By understanding how to configure and apply IDP policies, you can take a proactive approach to network security. This knowledge is not only crucial for the JNCIS-ENT certification but also for any network engineer looking to enhance their security skills.

Remember, the key to effective IDP is not just in the configuration but also in the ongoing monitoring and analysis of your network traffic. Regularly review your IDP logs and adjust your policies as needed to keep your network secure.

© Ben Jacobson.RSS