Threat Detection Policies and Rules

• 1: Manage Threat Detection Policies
• 2: Manage Threat Detection Rules
• 3: Runtime Threat Detection Policy Tuning
• 3.1: The Falco Rules Tuner (Legacy)

This page introduces Sysdig threat detection policies and the rules that comprise them, providing the conceptual background needed to create, edit, and apply security policies in your own environment.

Understanding Threat Detection Policies

A Sysdig Secure policy is a combination of rules about activities an enterprise wants to detect in an environment, the actions that should be taken if the policy rule is breached, and– potentially– the notifications that should be sent. A number of policies are delivered out-of-the-box and can be used as-is, duplicated, or edited as needed. You can also create policies from scratch, using either predefined rules or creating custom rules.

Managed Policies, Managed Rulesets, and Custom

As of July, 2022, threat detection policies have three “flavors.”

• Default/Managed Policies These are the default policies provided and managed by Sysdig. The Sysdig Threat Research team may update them at any time.

  • Default policies exist across all accounts, the names cannot be changed, and they cannot be deleted.

  • They are loaded with a pre-defined enabled/disabled status, based on most common usage, but you can enable or disable them at will.

  • Only the Scope and Action (such as notification channel) can be edited.

    

  • Note: Earlier versions of Sysdig Secure had “default” policies that were not managed by Sysdig and used different naming. See the release notes for information about that transition.

  If you want to edit other attributes, you can Duplicate policies to create:

• Managed Ruleset Policies:

  • Name, Description, and Severity can also be edited

  • As with the default Managed policies, Managed Ruleset policies may be updated by the Sysdig Threat Research team.

  • Use case example: You need different scopes or actions (such as notification channels) for the same set of rules within a Managed Policy.

    

  If you want to change the rules in a policy, then you need:

• Custom Policies: These can be created three ways:

  • Converting a Default policy to Custom
  • Converting a Managed Ruleset policy to Custom
  • Creating a policy from scratch
  • (Any policies from before July, 2022 are auto-converted to Custom policies and continue to work as they did before.)

  Custom policies cannot be updated by the Sysdig Threat Research team. If/when Sysdig creates new rules, the user must apply them to custom policies themselves.

Reviewing the Runtime Policies List

Select Policies > Runtime Policies see the default policies you loaded into Sysdig Secure, as well as any custom policies you have created.

From this overview, you can:

See at a Glance

• Severity Level Default policies are assigned High, Medium, Low, or Info level severity, which can be edited.

• Enabled/Not Enabled Viewed by toggle position.

• Policy Summary Includes Update status, the number of Rules, assigned Actions to take on affected containers (Stop | Pause | Notify), and Capture details, if any.

• Policy Status: Default policies are “managed policies,” Ruleset are managed ruleset policies, and Custom policies may be user-designed from scratch or converted from default policies with changes to their rules.

• Policy Type icons

Take Action

From this panel you can also:

• Drill down to policy details (and potentially Edit them)

• Search and filter policies by name, policy name, severity level, policy type, or whether captures are enabled

• Enable/Disable a policy using the toggle

• Create a new policy using the +Add Policy button

Review Policy Types

Additional types are added periodically.

Runtime Policies

Workload Policy

Powered by the Falco engine, these provide a way to filter system calls using flexible condition expressions. See Using Falco within Sysdig Secure for more context.

List-Matching Policy

Policies using a simple matching or not-matching for containers, syscalls, processes, etc. See Understanding List Matching Rules for more context.

Drift Policy

Policy with a single rule that provides default drift detection and prevention.

See also: Understanding DriftControl and Additional Parameters for Drift Policy Type.

Machine Learning

Policy leveraging Machine Learning to provide advanced detection capabilities.

See also: Understanding Machine Learning and Additional Parameters for Machine Learning Policy Type.

Log-Detection Policies

Kubernetes Audit Policy

Powered by the falco engine, provide a way to filter Kuernetes audit logs using flexible condition expressions. See also Kubernetes Audit Logging.

AWS CloudTrail Policy

Provides a way to filter AWS CloudTrail events using Falco-compatible condition expressions. You need to have Sysdig Secure for cloud installed to transmit your AWS CloudTrail events.

GCP Audit Log Policy

Provides a way to filter GCP audit logs using Falco-compatible condition expressions.

Azure Platform Log Policy

Provides a way to filter Azure platform logs using Falco-compatible condition expressions.

Scopes and Actions for Policy Types

The scopes and actions available differ by type:

	Scope Options	Action Options
RUNTIME
Workload	Custom Hosts only Container only	Stop/ pause/ kill Capture Notification channel
List-Matching	Custom Hosts only Container only	Stop/ pause/ kill Capture Notification channel
Drift	Custom only	Prevent Notification channel
LOG DETECTION
Kubernetes	kubernetes.cluster.name kubernetes.namespace.name	Notification channel
AWS Cloud	aws.accountId aws.region	Notification channel
GCP	gcp.projectid gcp.location	Notification channel
Azure	azure.subscriptionId azure.tenantId azure.location azure.resourceGroup	Notification channel

Understanding DriftControl

Drift is the change in an environment that differs from the expected state checked into a version control system, e.g. software that was introduced, updated, or upgraded into a live environment.

Sysdig’s DriftControl feature uses various detection techniques, such as watching the system for when new executables are downloaded, updated, or modified inside a container which was not part of the container image before the container started up.

With the default agent configuration, a Drift policy/rule will stop such a detected process after it has begun.

If it is necessary to ensure that a particular task should be blocked from ever starting, you can enable the following configuration in the agent config file:

drift_killer:
        enabled: true

Or if using helm, add the --set agent.sysdig.settings.drift_killer.enabled=true flag.

Be aware that this option uses ptrace, which is more resource-intensive than the default mode.

Understanding Machine Learning Policies

Prerequisite: Machine Learning policies require enabling the Profiling Sysdig Labs toggle to activate the underling fingerprint collection mechanism.

Machine Learning collects low-level activities from your infrastructure, aggregating them over time and applying algorithms.

With machine learning policies you can configure the detections you want to use and their thresholds.

Machine Learning Detection algorithms work by estimating the probability that those activities are related the detection subjects, i.e. miners. Sysdig Machine Learning detections don’t rely on mere program names or executable checksums matching. Instead, they are based on actual runtime behaviors, collected in the form of fingerprints by the Profiling feature.

Understanding How Policy Actions Are Triggered

Policy actions occur asynchronously. If a policy has a container action and matched activity, the agent asks the Docker/Cri-o daemon to perform the stop/kill/pause action. This process takes a few minutes, during which the container still runs and the connect/accept etc. still occurs.

Understanding Threat Detection Rules

Rules are the fundamental building blocks you will use to compose your security policies. A rule is any type of activity that an enterprise would want to detect in its environment.

Rules can be expressed in two formats:

• Falco rules syntax, which can be complex and layered. All the default rules delivered by Sysdig are Falco rules, and users can also create their own Falco rules.

• List-matching rules syntax, which is simply a list against which a match/not match condition is applied. All these rules are user-defined. They are grouped into five types: Container Image, File System, Network, Process, and Syscall.

Understanding the Rules Library

The Rules Library includes all created rules which can be referenced in policies. Out of the box, it provides a comprehensive runtime security library with container-specific rules (and predefined policies) developed by Sysdig’s threat-research teams, Falco’s open-source community rules, and international security benchmarks such as CIS or MITRE ATT&CK.

Audit-Friendly Features

In the Rules Library interface, you can see at a glance:

• Published By:

• Last Updated

for enhanced traceability and audit.

• Default rules appear in the UI as Published By: Sysdig
• User-defined rules appear as Published By: Secure UI

Tags

Rules are categorized by tags, so you can group them by functionality, security standard, target, or whatever schema makes sense for your organization.

Various tags are predefined and can help you organize rules into logical groups when creating or editing policies.

Search

Use the search boxes at the top to search by rule name or by tag.

Using Falco within Sysdig Secure

What is Falco

Falco is an open-source intrusion detection and activity monitoring project. Designed by Sysdig, the project has been donated to the Cloud Native Computing Foundation, where it continues to be developed and enhanced by the community. Sysdig Secure incorporates the Falco Rules Engine as part of its Policy and Compliance modules.

Within the context of Sysdig Secure, most users will interact with Falco primarily through writing or customizing the rules deployed in the policies for their environment.

Falco rules consist of a condition under which an alert should be generated and an output string to send with the alert.

Conditions

• Falco rules use the Sysdig filtering syntax.

  (Note that much of the rest of the Falco documentation describes installing and using it as a free-standing tool, which is not applicable to most Sysdig Secure users.)

• Rule conditions are typically made up of macros and lists.

  • Macros are simply rule condition snippets that can be re-used inside rules and other macros, providing a way to factor out and name common patterns.

  • Lists are (surprise!) lists of items that can be included in rules, macros, or other lists. Unlike rules/macros, they can not be parsed as Sysdig filtering expressions.

Behind the scenes, the falco_rules.yaml file contains the raw code for all the Falco rules in the environment, including Falco macros and lists.

Anatomy of a Falco Rule

All Falco rules include the following base parameters:

• rule name: default or user-assigned

• condition: the command-line collection of fields and arguments used to create the rule

• output:

• source:

• description:

• tags: for searching and sorting

• priority

Select a rule from the Rules Library to see or edit its underlying structure. The same structure applies when creating a new Falco rule and adding it to the library.

Existing Rule
Create a Rule

Falco rules with the source k8s_audit need Kubernetes Audit logging enabled for conditions to be met.

About Falco Macros

Many of the Falco rules in the Rules Library contain Falco macros in their condition code.

You can browse the Falco Macros list, examine a macro’s underlying code, or create your own macro. The default Falco rule set defines a number of macros that make it easier to start writing rules. These macros provide shortcuts for a number of common scenarios and can be used in any user-defined rule sets.

About Falco Lists

Default Falco lists are added to improve the user experience around writing custom rules for the environment.

For example, the list allow.inbound.source.domains can be customized and easily referenced within any rule.

(On-Prem Only) Upgrading Falco Rules with the Rules Installer

Sysdig Secure SaaS is always using the most up-to-date Falco rules set.

Sysdig Secure On-Prem accounts should upgrade their Falco rules set regularly.

This can be achieved through our Rules Installer.

Understanding List-Matching Rules

List-matching rules (formerly known as “fast” rules) are used for matching against lists of items (when matchItems=true) or matching everything other than lists of items (when matchItems=false). They provide for simple detections of processes, network connections, and other operations. For example:

• If this process is detected, trigger an action when this rule is in a policy (such as send notification).

  Or

• If a network connection on x port is detected, trigger an action when this rule is in a policy (such as send notification)

Unlike Falco rules, the list-matching rule types do not permit complex rule combinations, such as “If a connection on x port from y IP address is detected…”

The five list-matching Rule Types are described below.

Container Rules

These rules are used to notify if a specific image name is running in an environment. The rule is evaluated when the container is started. The items in the list are image pattern names, which have the syntax <host.name>:<port>/<name>/<name2>:<tag>@<digest>.

Only <name2> is required; everything else is optional and inferred building on the name.

See also: How Matching Works: Container Example and Create a List-Matching Rule: Container Type Example.

File System Rules

These rules are used to notify if there is write activity to a specific directory/file. The rule is evaluated when a file is opened. The items in the list are path prefixes.

For example: /one/two/three would match a path /one/two/three, /one/two/three/four, but not /one/two/three-four.

Network Rules

These rules are used to:

• Detect attempts to listen for inbound connections on ports on a specific list

• Generally identify any inbound or outbound connection attempts

Note that the current Sysdig UI talks about “Allowing” or “Denying” connections with network rules, but this can introduce some confusion.

For both Inbound and Outbound connections:

• Allow means do nothing

• Deny means match any attempt to make an inbound or outbound a connection

You would still need to add the rule to a policy and attach actions to respond to a connection attempt by stopping/pausing/killing the container where the connection occurred. See also: Understanding How Policy Actions Are Triggered.

Process Rules

These rules are used to detect if a specific process, such as SSH, is running in a particular area of the environment.

The rule is evaluated when a process is launched. The items in the list are process names, subject to the 16-character limit enforced by the Linux kernel. (See also: Process Name Length information.)

Syscall Rules

The syscall rule type is almost never deployed in user-created policies; the definitions below are for information only.

These rules are used (internally) to:

• Notify if a specific syscall happens in a list

• Notify if a syscall outside this trusted list happens in the environment

The rule is evaluated on syscalls that create inbound (accept, recvfrom, recvmsg, listen) and/or outbound (connect, sendto, sendmsg) connections. The items in the list are port numbers.

How Matching Works: Container Example

A Container Image consists of the following components:

<registry host>:<registry port>/<image>:<tag>@<digest>.

Note that <image> might consist of multiple path components such as <project>/<image> or <project>/<subproject>/<image>.

Complete example: docker.io:1234/sysdig/agent:1.0@sha256:da39a3ee5e6b4b0d3255bfef95601890afd80709

Where:

<registry host> = docker.io

<registry port> = 1234

<image> = sysdig/agent

<tag> = 1.0

<digest> = sha256:da39a3ee5e6b4b0d3255bfef95601890afd80709

Each item in the containers list is first broken into the above components, using the following rules:

• If the string ends in /, it is interpreted as a registry host and optional registry port, with no image/tag/digest provided.

• Otherwise, it is interpreted as an image. The registry host and port may precede the image and are optional, and the tag and digest may follow the image, and are optional.

Once the item has been broken into components, they are considered a prefix match against candidate image names.

Examples:

docker.io:1234/sysdig/agent:1.0 @sha256:da39a3ee5e6b4b0d3255bfef95601890afd80709: must match all components exactly

docker.io:1234/sysdig/agent:1.0: must match the registry host, port, image, and tag, with any digest

docker.io:1234/sysdig/agent: must match the registry host, port, and image, with any tag or digest

sysdig/agent: must match the image, with any tag or digest. Would not match an image docker.io:1234/sysdig/agent, as the image provides additional information not in the match expression.

docker.io:1234/: matches all images for that registry host and port

docker.io/: matches all images for that registry host

Getting Started

• Manage Policies

• Manage Rules

There are optional tools to help automate the creation of policies. See also: Network Security Policy Tool to author and fine-tune Kubernetes network policies

1 - Manage Threat Detection Policies

Overview

Review Threat Detection Polices, if needed.

In general, users will:

• Use Default Managed policies out-of-the-box, defining only the Scope , actions such as Nofication Channels, and enabling/disabling the policy;
• Duplicate a policy to create a Managed Ruleset and edit additional parameters such as Name, Description, and Severity, creating Managed Ruleset policies;
• Require Custom rules and either convert an existing policy or build policy parameters and ruleset from scratch.

Steps to Create a Custom Policy from Scratch

1. Log in to Sysdig Secure and select Policies > Runtime Policies.

2. On the Runtime Policies list page, select +Add Policy.

3. Select Type: Select the policy type and define the policy parameters. Note: The Scope available will differ by policy type.

4. Define parameters: E.g., Name, Description, Severity, etc. Most policy types have the same parameters; Drift and Machine learning have some differences.

5. Add rules: Add or edit the rules to be used.

6. Define actions: to be taken if the policy rules are breached.

7. Enable and Save the policy.

Details in the following sections.

Policy Details

Select the Policy Type

When you click +Add Policy, you are prompted to choose the Policy Type desired. See also: Review Policy Types

Define the Basic Parameters

The Policy parameters differ mainly by the Scope and Actions available on the type selected.

• Name and Description: Provide meaningful, searchable descriptors

• Enabled/Disabled: Once enabled, the policy will begin to generate events.

• Severity: Choose the appropriate severity level as you would like to see it in the Runtime Policies UI.

  Policy severity is subjective and is used to group policies within a Sysdig Secure instance.

  NOTE: There is no inheritance between the underlying rule priorities and the severity you assign to the policy.

• Scope: Define the scope to which the policy will apply, based on the type-dependent options listed.

• Link to Runbook: (Optional) Enter the URL of a company procedure that should be followed for events resulting from this policy. E.g. https://www.mycompany.com/our-runbook-link.

  If you enter a value here, then a View Runbook option will be displayed in any corresponding Event.

Additional Parameters for Drift Policy Type

The Drift policy differs from the other policy types in a few ways:

• 1:1 Policy:Rule Drift includes only one rule.
• Prevent You can toggle the Prevent action to stop the binary ever from starting.
• Dynamic Deny List When enabled, the policy evaluates and tracks any downloaded executable on the container. If that executable attempts to run, Sysdig will create an alert, or the executable is denied from running if Prevent is enabled.
• Exceptions A user-defined list that can allow a downloaded executable to not trigger an alert
• Always Deny A user-defined list that will always block the executable from running even if it was built with the image

Additional Parameters for Machine Learning Policy Type

The Machine Learning policy differs from the other policy types in a few ways:

• Detection types You can what type of Machine Learning based detections you want enable in your policy. We support only Crypto Mining Detection at this time.
• Confidence level You can fine-tune the policy to choose at which certainty level the detection should trigger an event.
• Severity defined at detection level, so that you can have a different severity for each detection type.

Add Rules

You can select existing rules from the Library or create new rules on the fly and add them to a policy.

The Policy Editor interface provides many flexible ways to add rules to or remove rules from a Policy; the instructions below demonstrate one way.

See also: Manage Rules

Import from Library

1. From the New Policy (or Edit Policy) page, click Import from Library.

   The Import from Rules Library page is displayed.

   

2. Select the checkboxes by the rules to import.

3. Click Mark for Import.

   

   A blue Import icon

   

   appears to the right of the selected rules and the Import Rules button is activated.

   

4. Click Import Rules.

   The Policy page is displayed with the selected rules listed.

   

Create a Rule from the Policy Editor

If you click New Rule instead of Import from Library, you will be linked to the procedure described in Create a Rule.

Define Actions

Determine what should be done if a Policy is violated. See also: Understanding How Policy Actions Are Triggered.

Containers

Select what should happen to affected containers if the policy rules are breached:

• Nothing (alert only): Do not change the container behavior; send a notification according to Notification Channel settings.

• Kill: Kills one or more running containers immediately.

• Stop: Allows a graceful shutdown (10-seconds) before killing the container.

• Pause: Suspends all processes in the specified containers.

For more information about stop vs kill command, see Docker’s documentation.

security:
  ignore_container_action: true

Capture

Toggle Capture ON if you want to create a capture in case of an event, and define the number of seconds before and after the event that should be in the snapshot.

As of June, 2021, you can add the Capture option to policies affecting events from both the Sysdig agent and Fargate Serverless Agents Fargate serverless agents. Note that for serverless agents, manual captures are not supported; you must toggle on the Capture option in the policy defintion.

See also: Captures.

Notification Channels

Select a notification channel from the drop-down list, for sending notification of events to appropriate personnel.

See also: Set Up Notification Channels.

Duplicate or Convert a Managed Policy

Select a row in the Runtime Policies list to expand the policy details and access the icons to Edit, Copy, or Delete the policy.

Duplicate to Create a Managed Ruleset

1. Select a Managed Policy in the Runtime Policies list and click the Duplicate icon in the details panel.

2. Optionally edit any of the parameters except the rules.

3. Click Save.

   The new policy will appear in the Runtime policy list tagged Ruleset.

   Note you can also duplicate a Ruleset, if desired.

   If the Sysdig Threat Research team updates the underlying ruleset in the Default policy on which it was based, the Managed Ruleset policy will be updated accordingly.

Convert to Create a Custom Policy

1. Select a Default or a Ruleset policy from the Runtime Policies list and click the Edit icon in the details panel.

2. Click the Convert to Custom button in the middle of the page.

   You can now edit everything about this policy, including the rules. It will not be managed/updated by the Sysdig team; if new rules are offered, the user is responsible for adding them to the custom policies as desired.

3. Click Save.

   Duplicating a custom policy simply creates another unmanaged custom policy.

Edit a Policy

Only certain changes can be made to a managed policy:

• Enable/disable the policy
• Set policy scope
• Set notifications
• New: Disable (or re-enable) individual rules (also available for custom policies)

Disable Individual Rules

As of September, 2022, you can disable individual rules within any policy or managed ruleset.

The primary use cases for this feature are:

• Using a subset of rules in a policy while retaining the “managed” status of the policy/ruleset and continuing to receive any updates that are pushed from Sysdig
• Temporarily disabling a rule that is generating many events, until the cause is investigated or an appropriate exception is put in place.

To disable a rule:

1. Select a threat detection policy from the Policies list and click the Edit (pencil) icon in the slide-out panel.

   The Policy details page is displayed.

   

2. Slide the toggle left for the rule(s) you want to disable.

3. Click Save.

2 - Manage Threat Detection Rules

Review Understanding Threat Detection Rules to get started.

Access the Rules Library

1. Select Policies > Rules | Rules Library.

2. The Rules Library is displayed.

   

Tips:

• Rules are listed alphabetically by name.

• Search: Click the magnifying glass if the Search field is not automatically opened. Search by words in the rule name.

• Published by: Remember that default (Falco) rules show up as Published by: Sysdig ; user-created rules show as Published by: Secure UI. See also: Edit a Rule.

• Usage: Shows number of policies where the rule and used, and whether the policies are enabled. Click the rule to see the policy names in the Rule Detail panel.

Create a Rule

There are different interfaces for creating Falco rules vs. list-matching rules.

Create a Falco Rule

1. From the Rules Library page, click +Add Rule and select Falco from the drop-down.

   The New Rule page for the Falco rule type is displayed.

   

2. Enter the parameters:

   Name and Description: create a name and a meaningful description for the rule

   Condition and Output: write the condition code and outputs required. See Supported Fields for more information.

   Priority: This is a required field to meet the Falco rule syntax.

   

   Source: Define if the rule is detecting events using the Kubernetes Audit data source or using the standard syscall mechanisms

   Tags: Select relevant tags from the drop-down or add your own custom tag

3. Click Save.

Create a List-Matching Rule: Container Type Example

Suppose you want detect whenever someone used a specific container image that has known problems. In this case, a Container rule would be appropriate. (The other list-matching rule types have similar entry fields, as appropriate to their type.)

1. From the Rules Library page, click +Add Rule and select Container from the drop-down.

   The New Rule page for the Container rule type is displayed.

   

2. Enter the parameters:

   Name: Enter a Name, e.g. Problematic Images.

   Description: Enter a Description, e.g. Images that shouldn’t be used

   If Matching/ If Not Matching: Select If Matching. When added to a policy, if the rule conditions match, then the policy action you define (such as “send notification”) will be triggered.

   Containers: Add the container name(s) that are problematic, e.g. cassandra:3.0.23.

   Tags: Select relevant tags from the dropdown, e.g. database and container.

3. Click Save.

Review a Rule Detail Panel

From the Rules Library list, select a rule to see its details.

From here you can:

• Review the rule definition, including clicking embedded macros to open their details in a pop-up window

• See all the tags associated with the rule (colored boxes)

• Check all policies in which the rule is used and see whether those policies are enabled or disabled.

Edit a Rule

Any rules published by Sysdig are default and are read-only. You can append to their lists and macros, but cannot change the core parameters. Default rules cannot be deleted.

Self-created rules can be freely edited. You can also override the behavior of default Falco rules and macros using a placholder mechanism in the Rules Editor.

To display existing rules:

1. Select Policies > Rules | Rules Library and select a rule.

2. The Rule Details panel opens on the right. You can review the parameters and append to macros and lists inline if desired.

   

Append to Falco Macros and Lists

Default Falco rules have a variety of macros and lists embedded in them. While these cannot be deleted from a default rule, you can append additional information onto them.

For example, consider the Policy DB Program Spawned Process in the screenshot above. The embedded rule is used to check that databases have not spawned illicit processes. You can see in the rule condition the Falco list : db_server_binaries.

To append items in a default list:

1. Click the blue list text in the rule condition, or go to Policies > Falco Lists and search for it by name.

   

2. The list content is displayed. Click Append.

   

3. Enter the additional items (i.e. databases) you want to include in the rule and click Save.

   The same process applies to macros.

How to Use the Rules Editor

The Rules Editor allows you can freely create custom Falco rules, lists, and macros and can override the behavior of the defaults.

Understand the Interface

To access the interface, select Policies > Rules Editor:

The Right Panel (Default)

Displays the rules_yamls provided from Sysdig.

• Contains the default rules and macros

• Is read-only

The Left Panel (Custom)

Displays the custom rules and overrides you want to add to the selected rules_yaml.

Note that many default Falco rules and macros have a parallel placeholder entry (commented out) in the yaml file. These have the prefix user_known. To change the behavior of a default rule, it is recommended to copy the placeholder equivalent into the custom rules panel and edit it there, rather than editing the default rule directly.

To search the rules YAML files

Click inside the Rules Editor right panel and use CNRL F to open an internal search field .

See also: Runtime Policy Tuning .

Use Cases: List-Matching Rules

It is more helpful to think of the rules as matching the activity, rather than using concepts of allowing or denying. (The Network types can be a little confusing in this regard; see the last two use cases for more detail on that type). Thus, the use cases are based on answering the question: What do I want to know?

I WANT TO KNOW…

when any process other than web server programs are run:

• Rule Type: Process

• If Not Matching

• Entries: [apache, httpd, nginx]

if any of the following crypto-mining processes are run:

• Rule Type: Process

• If Matching

• Entries: [minerd, ccminer]

if any program reads any file containing password-related information:

• Rule Type: Filesystem

• Read Operations: If Matching

• Entries: /etc/shadow, /etc/sudoers, /etc/pam.conf, /etc/security/pwquality.conf

if any program writes anywhere below binary directories:

• Rule Type: Filesystem

• Read/Write Operations: If Matching

• Entries: /usr, /usr/bin, /bin

if a program writes to anywhere other than /var/tmp:

• Rule Type: Filesystem

• Read/Write Operations: If Not Matching

• Entries: /var/tmp

if any container with an image from docker.io is started:

• Rule Type: Container

• If Matching

• Entries: [docker.io/]

if any container runs an Apache web server:

• Rule Type: Container

• If Matching

• Entries: [httpd, amd64/httpd]

I want to know if any container with a non-database image is started:

• Rule Type: Container

• If Not Matching

• Entries [percona/percona-server, mysql, postgres]

if any program accepts an inbound ssh connection:

• Rule Type: Network

• Tcp, "If Matching"

• Entries: [22]

if any program receives a DNS datagram:

• Rule Type: Network

• UDP, "If Matching"

• Entries: [53]

if any program accepts a connection on a port other than http/https

• Rule Type: Network

• TCP, "If Not Matching"

• Entries: [80, 443]

if any program accepts any inbound connection:

• Rule Type: Network

• Inbound Connection: Deny

if any program makes any outbound connection

• Rule Type: Network

• Outbound Connection: Deny

3 - Runtime Threat Detection Policy Tuning

The Runtime Policy Tuning feature assists in reducing noisy false positives in the Sysdig Secure Events feed. Built on top of the Falco Rules Tuner, it automatically adds Exceptions to rules, thereby removing particularly noisy sets of policy events and leaving the lower-volume events for later analysis.

The tuner may be especially helpful when deploying Sysdig Secure runtime policies in a new environment. Your environment may include applications that legitimately perform actions such as running Docker clients in containers, changing namespaces, or writing below binary directories, but which trigger unwanted floods of related policy events in the default policies and rules provided by Sysdig.

Using Runtime Policy Tuner

Prerequisites

• Sysdig agent 11.0.0+

• Sysdig SaaS or Sysdig On-Prem 5.0+

Enable, View, Edit Exceptions, Disable

The tuner is enabled and disabled as needed to tame false positives and optimize the use of the Events feed. By default, it is disabled.

1. Log in to Sysdig Secure as Admin and choose Policies > Threat Detection | Runtime Policy Tuning.

2. Enable the feature with the Tuning Engine toggle.

   It may take up to 24 hours to see the initial Applied Tuning Exceptions listed in the left panel.

   

   In the background, the tuner will evaluate policy events as they are received by the Sysdig backend, find applicable exceptions values, and add them. The AppliedTuning Exceptions file is passed along to all Sysdig agents, along with the rules and policies.

3. If needed, you can edit the Exceptions created directly in the left-hand panel.

   Any changes will be retained as the tuner evaluates additional events.

   NOTE: Do not add custom exceptions, macros, or lists definitions here. Please use the Rules Editor (Custom Rules) for such elements.

4. Toggle the Tuning Engine off when you feel the feature has addressed the most commonly occurring (unwanted) policy events.

   NOTE: Any exceptions in the Applied Tuning Exceptions panel will still be passed along to agents.

   To start over from scratch, clear the Applied Tuning Exceptions text and re-enable with the Tuning Engine toggle.

Understanding How the Tuning Engine Works

When Does the Tuner Add Exceptions?

The Policy Tuning feature is conservative, only adding exceptions for commonly occurring events for a single rule with similar attributes.

All the conditions must be met:

• The rule has generated at least 25 policy events in the past hour

• A candidate set of exception values is applicable to at least 25% of the events in the past hour

This ensures the tuning feature only adds exceptions for high-volume sets of events that can be easily addressed with a single set of exception values.

Exceptions Behind the Scenes

If you want to understand the process of exception insertion by the tuner, consider a sample rule:

- rule: Write below root
  desc: an attempt to write to any file
   directly below / or /root
  condition: root_dir and evt.dir = < and
   open_write
  exceptions:  - name: proc_writer
  fields: [proc.name, fd.filename]

And a stream of policy events with outputs such as:

File below / or /root opened for writing (user=root user_loginuid=-1 command=/usr/local/bin/my-app-server parent=java file=/state.txt program=my-app-server container_id=a97d44bbe437 image=my-registry/app-server:latest
File below / or /root opened for writing (user=root user_loginuid=-1 command=/usr/local/bin/my-app-server parent=java file=/state.txt program=my-app-server container_id=a97d44bbe437 image=my-registry/app-server:latest
File below / or /root opened for writing (user=root user_loginuid=-1 command=/usr/local/bin/my-app-server parent=java file=/state.txt program=my-app-server container_id=a97d44bbe437 image=my-registry/app-server:latest
File below / or /root opened for writing (user=root user_loginuid=-1 command=/usr/local/bin/my-app-server parent=java file=/state.txt program=my-app-server container_id=a97d44bbe437 image=my-registry/app-server:latest

Then the tuner would add the following exception values to address the false positives:

- rule: Write below root
  exceptions:
  - name: proc_writer
    values:
       - [my-app-server, /state.txt]
   append: true

See the Falco proposal for more background information on using exceptions.

3.1 - The Falco Rules Tuner (Legacy)

Sysdig policies are built on rules, including Falco rules and macros. (For review: Understanding Sysdig Secure Rules and Using Falco within Sysdig Secure.) Sysdig is always working to improve its out-of-the-box policies based on activity captured about well-known containers and OSS applications. Nevertheless, proprietary software running in unique user environments can require a customized approach.

The Falco Rule Tuner was created to simplify the process of updating the existing ruleset to reduce false positives.

The tool fetches policy events generated during a configurable time window (EVENT_LOOKBACK_MINUTES), and based on occurrence threshold (EVENT_COUNT_THRESHOLD), it suggests updates to rules. It’s up to the user to evaluate the suggestions and selectively apply the changes.

To use the Rule Tuner, you will provide some environment variables, run as a Docker container, review the output in a Slack channel or the terminal window, and then apply the recommended tuning adjustments as desired, in the Sysdig Secure Rules Editor.

Requirements

• Sysdig Secure SaaS or On-Prem version 3.5.0+

• An available Slack channel (optional, for receiving output information)

• Environment variable values listed in the table below

Set Variables and Run the Container

Gather the values needed for the following environment variables.

Required Environment Variables for Falco Rule Tuner

Run as a Docker container:

docker run -e SECURE_ENDPOINT=${SECURE_ENDPOINT} -e SECURE_TOKEN=${SECURE_TOKEN} quay.io/sysdig/falco_rules_tuner

The output in the terminal window will show the recommended rules to be adjusted and the recommended/generated macros and their conditions, e.g.:

... <etc.>

# Change for rule: Write below root
- macro: elasticsearch-scripts_python_access_fileshost_exe_access_files
  condition: (container, image, repository endswith locationservices/elasticsearch-scripts and proc.name=python and (fd.name startswith=/root/app/))

Check Output in Slack Channel (Optional)

The output provided in the terminal window includes only the recommended rule changes. If you provide a Slack channel URL in the environment variables, the Tuner gives both an event summary and the recommended rule changes.

Apply Recommended Tuning to Rules

For review: How to Use the Rules Editor.

The Tuner detects rules that may be triggering excess alert “noise” and proposes content relevant macros and macro conditions that would reduce the noise.

To implement the suggestions, you can 1) copy the rule contents directly into the left panel of the Rules Editor and edit them, or 2) find the existing placeholder macro that was created for that rule (usual format: user_known_<rule_name> ) and add the suggested macros and conditions there.

Note that editing the definition of a rule directly could cause overwrite issues when upgrading Sysdig versions. Creating custom rules or using the user_known placeholders is a safer procedure.

For example, suppose you decide to implement the Tuner prompt 4 in the image above, which suggests changing the configuration of the rule Write below root. One way to proceed:

1. Search [CTRL F] the falco_rules.yaml for Write below root.

   You will find both the Rule itself

   

   and placeholder macros, user_known_write_below_root_activities and user_known_write_below_root_conditions. Either one can be used.

   

2. Copy one placeholder to the left-hand Custom Rules panel of the Editor: user_known_write_below_root_activities .

3. Copy the tuner-generated macro (elasticsearch-scripts_python_access_files in this case), and conditions into the Custom Rules panel, overwriting the never_true default condition. The result is something like:

   # generated by tuner and copied to here (custom panel in the rules editor)
   - macro: elasticsearch-xxx
     condition: (...)
   - macro: user_known_write_below_root_acitivies
     condition: (elasticsearch-xxx) # updated from "never_true" with the generated macro name
   

4. Click Save.

   The tuning adjustment will apply when the Write below root rule is invoked in a policy.