Create a new custom detection rule

Create a custom detection rule for cloud workload security risks.

Creating Custom Detection Rules gives you the flexibility to define and enforce security best practices tailored to your organization's objectives. Use them to detect the conditions, misconfigurations, and policy violations that matter to your organization but are not covered by the built-in rules that ship with Cortex Cloud.

Note

A rule only detects criteria for evaluation, but do not initiate any actions unless incorporated within a policy.

To act on a detection, add the rule to a policy (to create issues or enforce prevention) and, optionally, associate it with a custom control so violations appear in your compliance reports.

Before you begin

Ensure you have a custom compliance control defined to associate the Custom Detection Rule to. For more information, see Use a built-in or custom standard.

How to create a custom detection rule

1. Go to Posture Management → Rules & Policies → Rules → Cloud Workload.
2. In the Cloud Workload Rules page, select Create Custom Rule.
3. Enter the following settings:

   • Rule name: A descriptive name for the custom rule.
   • Description: An optional field for adding additional details or context about the rule, such as its purpose or intended behavior.
4. Select a Scanner. A scanner determines the rule language, rule input, and assets that the rule can inspect.

Use the following table to select a scanner:

Scanner	Language	Input your rule receives	Use it to
Agentless disk scan	Rego	File content and metadata for each file you declare	Inspect disk-image files, such as /etc/ssh/sshd_config or /etc/shadow
Kubernetes connector	Rego	The Kubernetes resource object being evaluated	Inspect Kubernetes resources, such as Deployments, Services, and RBAC roles
XDR agent	Python	Data that the script reads directly from the host	Run read-only Python scripts for custom host checks

Note:

Each scanner delivers input in a different structure. Writing your rule against the wrong structure produces a rule that never matches and reports no error. Review the input structure for your chosen scanner before writing detection logic.

1. Configure the scanner-specific settings:

Agentless Disk Scan settings

The Agentless disk scan evaluates files on a disk image using rules written in Rego. Each rule evaluates the file content and metadata provided by the scanner through a defined input structure.

Field	Description
Operating System	The operating system targeted by the rule. The available options are: Linux Windows
Input file(s) path	The full file path for one or more files. For example, /nfs/an/disks/jj/home/dir/file.txt
Define the Rule (Rego)	Agentless disk scan rules use the following structure: Declare the panw.compliance package. Import rego.v1. Define one or more match rules to specify the detection logic. Assign a human-readable finding description to msg. package panw.compliance import rego.v1 match contains {"msg": msg} if { # Your detection logic here msg := "Description of the finding" } Use the default code in this box as a reference or starting point. For detailed configuration steps, see Configure Agentless disk scan rule.

Kubernetes connector Settings

Kubernetes Resources

From the list, select one or more from the following: Namespaces: Logical partitions within a Kubernetes cluster that allow resource isolation and organization. ReplicaSets: Ensures a specified number of pod replicas are running at all times by automatically scaling up or down. Deployments: Manages and controls pod replicas by providing declarative updates for ReplicaSets, enabling rolling updates and rollbacks. StatefulSets: Deploys stateful applications that require persistent identity and storage, ensuring stable pod names and ordered scaling. DaemonSets: Ensures that a copy of a specific pod runs on all or selected nodes in the cluster, commonly used for logging and monitoring agents. Jobs: Runs one-time or short-lived workloads that complete execution and then terminate. CronJobs: Defines scheduled jobs that run at specified times or intervals, similar to Linux cron jobs. ClusterRoles: Defines permissions at the cluster level, granting access to resources across all namespaces. Roles: Defines permissions within a specific namespace, restricting access to resources within that namespace. RoleBindings: Associates a role with a user, group, or service account within a specific namespace. ClusterRoleBindings: Associates a cluster role with users, groups, or service accounts at the cluster-wide level. NetworkPolicies: Defines rules that control the communication between pods and other network entities within the cluster, enforcing security restrictions. Services: Exposes a set of pods as a network service, allowing stable communication within and outside the cluster. ServiceAccounts: Provides an identity for pods to authenticate against the Kubernetes API, allowing controlled access to resources. Endpoints: Represents the actual network addresses of the pods backing a service, dynamically updated as pods start or stop. Ingresses: Manages external access to services, providing HTTP/HTTPS routing, load balancing, and SSL termination. ConfigMaps: Stores non-sensitive configuration data in key-value pairs, allowing applications to retrieve configuration without modifying container images. Secrets: Securely stores and manages sensitive data, such as API keys, passwords, and certificates, in an encrypted format. Nodes: Defines the physical or virtual machines that run the workloads in a Kubernetes cluster.

Define the Rule (Rego)

Kubernetes connector rules must use the following structure: Declare the panw.compliance package. Import rego.v1. Define one or more match rules to specify the detection logic. Assign a human-readable finding description to msg. package panw.compliance import rego.v1 match contains {"msg": msg} if { # Your detection logic here msg := "Description of the finding" } The rule is evaluated against each Kubernetes resource selected for the rule. When the detection conditions are satisfied, the match rule produces a finding containing the value assigned to msg. For detailed configuration steps, see Configure Kubernetes connector rule.

XDR agent Settings

Field	Description
Custom Code Execution	Note Enable this setting for the scanner to perform custom compliance checks by executing user-defined Python scripts. Only users with the following roles can enable or disable Custom Code Execution: Account Admin Instance Administrator Deployment Admin Privileged Security Admin Select Confirm to accept the terms and conditions in the dialog box. After you accept the terms, the remaining XDR agent settings appear.
Operating System	The operating system targeted by the rule. The available options are: Linux Windows
Define the Rule (Python)	XDR agent rules use a Python run function as the entry point. The function accepts positional and keyword arguments and returns the rule result. def run(*args, **kwargs): return {"result": True} For detailed configuration steps, see Configure XDR agent rule.

1. Define Compliance Violation Severity of the compliance violation to ensure proper categorization and prioritization. Possible values are:

   • Critical
   • High
   • Medium
   • Low
   • Informational
2. Assign Compliance Controls to one or more existing compliance controls.

NOTE

Only Custom Detection Rules (not built-in rules) can be assigned to custom controls.

   a. Click Add.    b. Select a custom compliance control from the list.    c. Click Assign.

1. For Remediation, you can optionally define the remediation steps to address any detected misconfiguration.
2. Select Create. The new rule appears in the Rules List. You can now use the rule as a check to either create an issue or monitor adherence to a specific requirement.

Create an issue

Under Posture Management → Policies → Cloud Workload, add the Custom Detection Rule to a Policy. This policy automatically runs the rule and creates an issue if the check fails.

Monitor compliance adherence

Under Posture Management → Compliance → Catalogs → Standards, create a custom standard that includes the custom control associated with the Custom Detection Rule, and then create an assessment profile that runs the custom standard. You can then monitor the compliance results in a report.

For detailed information, see Monitor and track compliance adherence.

Troubleshooting

Symptom	Cause	Resolution
The rule runs but does not produce a finding or report an error.	The rule accesses the scanner input using an incorrect structure.	Verify the input structure for the scanner. For Agentless Disk Scan, access files through input.files[id] and use fields such as f.path and f.content. For Kubernetes Connector, access the Kubernetes resource directly through fields such as input.kind, input.metadata, and input.spec.
A file permission comparison does not match the expected value.	The expected permission value is expressed in octal rather than decimal.	Convert the permission value to decimal. For example, 0600 is 384 and 0644 is 420.
The rule fails validation and cannot be saved.	The rule is missing one or more required elements.	Ensure that the rule declares package panw.compliance, imports rego.v1, and defines at least one match rule.
A directory check does not produce a finding.	The rule attempts to evaluate file content for a directory.	Check the file type before evaluating content. For example, use f.metadata.file_type == "file" to limit the logic to regular files.
A Python rule always passes.	The run function returns None or does not return a result value.	Return {"result": False, "cause": "<description>"} when a violation is detected. Return {"result": True} when the check passes.
A Python rule reports an error during execution.	The script does not define the required run function, or the script encounters an error during execution.	Define run(*args, **kwargs) as the entry point and verify that the script executes successfully using supported, read-only operations.