diff --git a/config/_default/menus/main.en.yaml b/config/_default/menus/main.en.yaml index b63e379a26435..8e0f0f7d2e722 100644 --- a/config/_default/menus/main.en.yaml +++ b/config/_default/menus/main.en.yaml @@ -6400,16 +6400,21 @@ menu: parent: workload_protection identifier: workload_protection_agent_expressions weight: 204 + - name: Writing Custom Rule Expressions + url: security/workload_protection/secl_auth_guide + parent: workload_protection_agent_expressions + identifier: workload_protection_secl_guide + weight: 1 - name: Linux Syntax url: security/workload_protection/linux_expressions parent: workload_protection_agent_expressions identifier: linux_expressions - weight: 1 + weight: 2 - name: Windows Syntax url: security/workload_protection/windows_expressions parent: workload_protection_agent_expressions identifier: windows_expressions - weight: 2 + weight: 3 - name: Coverage and Posture Management url: security/workload_protection/inventory parent: workload_protection diff --git a/content/en/security/workload_protection/guide/_index.md b/content/en/security/workload_protection/guide/_index.md index f1fe61ef649cd..c84b1d2cd7563 100644 --- a/content/en/security/workload_protection/guide/_index.md +++ b/content/en/security/workload_protection/guide/_index.md @@ -7,6 +7,6 @@ disable_toc: true {{< whatsnext desc="Use these end-to-end guides to accomplish specific goals:" >}} {{< nextlink href="/security/workload_protection/guide/active-protection" >}}Proactively block crypto mining threats with Active Protection{{< /nextlink >}} {{< nextlink href="/security/workload_protection/guide/tuning-rules" >}}Best Practices for Fine-Tuning Workload Protection Security Signals{{< /nextlink >}} - {{< nextlink href="/security/workload_protection/guide/custom-rules-guidelines" >}}Guidelines for Writing Custom Rules{{< /nextlink >}} + {{< nextlink href="/security/workload_protection/secl_auth_guide" >}}Writing custom rule expressions{{< /nextlink >}} {{< nextlink href="/security/workload_protection/guide/ebpf-free-agent" >}}Threat Detection for Linux Without eBPF Support{{< /nextlink >}} {{< /whatsnext >}} diff --git a/content/en/security/workload_protection/guide/custom-rules-guidelines.md b/content/en/security/workload_protection/guide/custom-rules-guidelines.md deleted file mode 100644 index 009ef8c5c4af5..0000000000000 --- a/content/en/security/workload_protection/guide/custom-rules-guidelines.md +++ /dev/null @@ -1,51 +0,0 @@ ---- -title: Guidelines for Writing Custom Workload Protection Rules -aliases: - - /security/cloud_security_management/guide/custom-rules-guidelines -further_reading: -- link: "/security/workload_protection/workload_security_rules" - tag: "Documentation" - text: "Managing Workload Protection Rules" -- link: "/security/workload_protection/agent_expressions" - tag: "Documentation" - text: "Agent Expression Syntax" ---- - -At some point, you may want to write your own [custom Workload Protection Agent rules][1]. When writing your own rules, there are a few strategies you can use to optimize for efficiency. - -## Attributes - -To ensure that your policy is evaluated in-kernel for maximum efficiency, always use one of the following attributes for rules on process or file activity: - -- `Agent Version >= 7.27` -- `process.file.name` -- `process.file.path` -- `[event_type].file.name` -- `[event_type].file.path` - -**Note**: Possible values for `[event_type]` include `open` or `exec`. - -## Wildcards - -Use wildcards (`*`) carefully. For example, never use `open.file.path =~ "*/myfile"`. If you must use wildcards prefixing directories, at least two levels are required: `open.file.path =~ "*/mydir/myfile")`. - -**Note**: You must append a tilde (`~`) to the [operator][2] when using wildcards. - -## Approvers and discarders - -Workload Protection uses the concept of approvers and discarders to filter out events that should not trigger any rules in a policy. Approvers and discarders allow or deny events at the policy level only. They do not act on individual rules. - -Approvers act as an allow-list at the kernel level in the Datadog Agent. For example, the opening of a specific file could be an approver on the event `open`, whereas `open` events on files without approvers would be filtered out. Similarly, discarders act as a deny-list in the Agent. Discarders intentionally filter out events that can never match a rule. The Agent learns which events to filter out with discarders during runtime. - -Approvers and discarders are generated based on your entire policy. Due to this, if a single rule does not make use of approvers for a given event (for example, `open` or `exec`), approvers cannot be used for that event for the entire policy, making every rule that uses that event less efficient. - -For example, if you used explicit filenames to evaluate `open` events for every rule but one (`open.file.path == "/etc/shadow"`, `open.file.path == "/etc/secret"` and so on.), and used a wildcard in that one event (`open.file.path == "/etc/*"`), the `open` event would not generate an approver, but may generate discarders during runtime. - -Approvers are generally more powerful and preferred. Using approvers, the Agent can process only what it needs to see rather than dynamically learning what to filter out. - -## Further Reading - -{{< partial name="whats-next/whats-next.html" >}} - -[1]: /security/workload_protection/workload_security_rules -[2]: /security/workload_protection/agent_expressions/#operators \ No newline at end of file diff --git a/content/en/security/workload_protection/secl_auth_guide.md b/content/en/security/workload_protection/secl_auth_guide.md new file mode 100644 index 0000000000000..be7e9e97ba8cc --- /dev/null +++ b/content/en/security/workload_protection/secl_auth_guide.md @@ -0,0 +1,202 @@ +--- +title: Writing Custom Rule Expressions +disable_toc: false +aliases: + - /security/cloud_security_management/guide/custom-rules-guidelines + - /security/workload_protection/guide/custom-rules-guidelines +--- + +This guide shows you how to write effective SECL (Security Language) rules for Datadog Workload Protection. + +## SECL overview + +Datadog SECL is a custom domain-specific language used to create Agent expressions and policies within Datadog Workload Protection. SECL allows security teams to define real-time threat detection rules by specifying conditions, operators, and patterns that security agents can monitor across hosts, containers, applications, and cloud infrastructure. + +## How SECL rules fit together + +Think of SECL as a local filter: it runs inside the Agent on each host, watching kernel and OS events. When an event matches your SECL expression, the Agent raises a detection. + +Datadog threat detection rules act as backend logic: they combine one or more Agent rules (using `@agent.rule_id`), add thresholds, suppress noise, and decide how alerts are routed. + +In summary, the Agent rule finds raw behavior and the detection rule turns it into a usable signal. + +
This guide describes how to create rule expressions manually, but Workload Protection also provides the Assisted rule creator wizard to walk you through creating the Agent and detections rules together. See Create the custom Agent and detection rules together.
+ +### Agent expression syntax + +The standard format of a SECL expression is: + +{{< code-block lang="plaintext" >}} +. [ .] ... +{{< /code-block >}} + +Using this format, an example rule for a Linux system looks like this: + +{{< code-block lang="plaintext" >}} + +open.file.path == "/etc/shadow" && process.file.path not in ["/usr/sbin/vipw"] + +{{< /code-block >}} + +## Quickstart + +Here's a summary of the process: + +1. Go to Workload Protection [Policies][1]. +2. Click **New Policy** to create a policy, or select an existing policy from the list to open it. +3. In the policy, click **Add Agent Rule**, and then click **Manual rule creator**. +4. In **Define the agent expression**, enter your expression using the following steps. +5. Select **Linux** or **Windows**. Most expression fields are OS-specific. +6. Choose a trigger (event type). Choose a trigger that aligns with the behavior you want to catch, but not everything that could happen. + - Examples: `exec`, `open`, `connect`, `create`, `dns`, etc. +7. Anchor the trigger on one or two stable fields. Example: + - Linux: `exec.file.path`, `process.ancestors.file.name`. + - Windows: `file.path`, `exec.args`, `open_key.registry.key_path`. +8. Add context to the trigger. Examples: + - Parent ancestry: `process.ancestors.*` + - User info: `process.user`, `process.uid` + - Containers: `container.*` + - Time: `process.created_at > 5s` +9. Insert safe exceptions. Examples: `not in [...]`, `!~`. In SECL, you can implement "allowlists" (the conditions that are included or excluded from detection) using ordinary operators like `not in`, `!~`, or conditional exclusions. +10. Name and save the rule. + +### Test the rule + +To view Agent events that match the expression, view the rule details, and then click **View Events**. The [Agent Events explorer][2] opens and displays the Agent events that match the expression. In **Agent Events**, you can see the raw telemetry: every kernel/OS event that matched the SECL rule before suppression or aggregation. + +When viewing raw Agent events, do the following: +1. Confirm the rule is firing on the intended activity. +2. Measure the scope and frequency across hosts/environments. +3. Decide if this is the expected baseline or a true threat. +4. If events are benign, add a suppression or update your expression with allowlist conditions. +5. If events are suspicious, escalate by passing the finding into your incident process, or take action to stop or isolate the suspicious workload. + +To test detection rules, view the rule details, and then click **[Number] detection rules found**. The Detection Rules explorer opens and displays the backend logic layer: the detection rule, linked signals, metadata, JSON definition, tags, and version history. + +When viewing the backend logic for a detection rule, do the following: + +1. Confirm that the rule name, description, and JSON (net_util_in_container) clarify what the rule is supposed to catch. +2. Measure whether the rule is noisy or precise by reviewing the aggregate metrics (query histogram, signals over time, affected hosts).. +3. Decide if the detected activity is expected (baseline) or suspicious (threat). +4. Suppress/allowlist if benign, escalate/contain if suspicious. + +## Rule authoring tips + +- Always set the operating system (OS). +- Anchor on ancestry to reduce noise. Use `process.ancestors.file.name`. +- Use durations (for example, `> 5s`, `10m`, `2h`) to target narrow execution windows. +- Use exact match (`==`) whenever possible as it results in the lowest noise. +- List membership (`in [...]`) is best for allowlists or controlled sets of values. +- Use a glob match (`~"/path/*"`) for path families as it is safer and faster than regex. +- Use regex (`=~`) only when globs/lists can't be used. Keep the regex expression as narrow as possible. As a rule of thumb, start with `==` or `in [...]`. Reach for regex only as a last resort. +- Use negation (`not in [...]`, `!~`) to carve out exceptions explicitly (for example, trusted tools). +- Use CIDR operators (`in CIDR`, `not in CIDR`) for network boundaries. +- Name rules by behavior, with a format that follows *What + Who + Context*. +- Tag generously: `team`, `app`, `env`, `MITRE`, `severity`. + + +### Avoid common mistakes + +| Pattern | Explanation | +| ------------------------- | -------------------------------------------- | +| `open.file.path == "/etc/passwd"`, `exec.comm != ""` | Too broad. Matches a lot of valid use cases. | +| `fd.name contains "/"` | Matches nearly every file I/O event. | +| `container.id != ""` | Useful only if scoped with a more specific field. | + +## Common building blocks + +For information and examples of common building blocks like operators, patterns, regular expressions, duration, and platform-specific syntax, see [Creating Agent Rule Expressions][3]. + +## Example library + +### Linux + +#### Access to sensitive files (allowlist safe tools) + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +open.file.path in ["/etc/shadow", "/etc/sudoers"] && +process.file.path not in ["/usr/sbin/vipw", "/usr/sbin/visudo"] +{{< /code-block >}} + +#### Nginx or PHP spawning bash + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +exec.file.path == "/usr/bin/bash" && +( + process.ancestors.file.name == "nginx" || + process.ancestors.file.name =~ "php*" +) +{{< /code-block >}} + +#### Suspicious IMDS access from container + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +connect && +network.destination.ip in ["169.254.169.254"] && +container.id != "" +{{< /code-block >}} + +#### Kernel module loads outside maintenance window + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +load_module && +process.user != "root" && +process.ancestors.file.name not in ["modprobe", "insmod"] +{{< /code-block >}} + +#### Sensitive file read shortly after start + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +open.file.path == "/etc/secret" && +process.file.name == "java" && +process.created_at > 5s +{{< /code-block >}} + +#### Outbound to non-corporate IPs (CIDR allowlist) + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +connect && +network.destination.ip not in [10.0.0.0/8, 192.168.0.0/16, 172.16.0.0/12] +{{< /code-block >}} + +### Windows + +#### Registry persistence via run key + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +set_key_value && +open_key.registry.key_path =~ "*\\Software\\Microsoft\\Windows\\CurrentVersion\\Run*" +{{< /code-block >}} + +#### Unsigned Binary Launching PowerShell + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +exec.file.path =~ "*\\WindowsPowerShell\\v1.0\\powershell.exe" && +process.parent.file.path !~ "*\\Program Files*" && +process.user_sid != "S-1-5-18" +{{< /code-block >}} + +### Cross-platform + +#### Crypto-miner indicators + +{{< code-block lang="plaintext" disable_copy="true" collapsible="true" >}} +exec.args_flags in ["cpu-priority", "donate-level", ~"randomx-1gb-pages"] || +exec.args in [~"*stratum+tcp*", ~"*nicehash*", ~"*yespower*"] +{{< /code-block >}} + +## Rollout strategy + +| Phase | Action | +| ------------ | ------------------------------------------------------------ | +| **Draft** | Author rule with YAML metadata and proper filters. | +| **Simulate** | Use Agent in read-only mode. | +| **Validate** | Run in staging workloads. Validate behavior with real events. | +| **Tune** | Add suppressions, `not in`, `container.image`, etc. | +| **Scale** | Reference in backend detection rules for full rollout. | + +After validatation and deployment, continue monitoring rule performance to keep false positives low and coverage strong as workloads evolve. + +[1]: https://app.datadoghq.com/security/workload-protection/policies +[2]: https://app.datadoghq.com/security/workload-protection/agent-events +[3]: /security/workload_protection/agent_expressions \ No newline at end of file diff --git a/content/en/security/workload_protection/workload_security_rules/custom_rules.md b/content/en/security/workload_protection/workload_security_rules/custom_rules.md index 88878e60cc3e5..8988b02919ea8 100644 --- a/content/en/security/workload_protection/workload_security_rules/custom_rules.md +++ b/content/en/security/workload_protection/workload_security_rules/custom_rules.md @@ -89,7 +89,7 @@ To use the Assisted rule creator: 1. Go to [Agent Configuration][3]. 2. Create or open a policy. -3. In **Actions**, select **Assisted rule creator**. +3. In **Add Agent Rule**, select **Assisted rule creator**. 4. Define the detection. To monitor your resource effectively, you have the following detection type options: - To detect nonstandard and suspicious changes to files, select **File integrity monitoring (FIM)**. - To track and analyze system software processes for malicious behavior or policy violations, select **Process activity monitoring**.