Sensor Tasking - Query and Command EDR Agents

This skill orchestrates sending tasks (commands) to EDR sensors and handling responses. It solves two key challenges of sensor tasking:

1. Offline agents: Sensors may be offline when you want to task them
2. Response collection: Some tasks generate data that needs to be collected

LimaCharlie Integration

Prerequisites: Run /init-lc to initialize LimaCharlie context.

LimaCharlie CLI Access

All LimaCharlie operations use the limacharlie CLI directly:

limacharlie <noun> <verb> --oid <oid> --output yaml [flags]

For command help and discovery: limacharlie <command> --ai-help

Critical Rules

When to Use

Use this skill when the user wants to:

• Live Response: Query running processes, network connections, registry keys, services
• Forensic Collection: Collect memory maps, file listings, autoruns, packages
• Fleet Operations: Execute commands across many sensors (by tag, platform, etc.)
• Incident Response: Isolate hosts, kill processes, gather evidence
• Data Collection at Scale: Get OS versions, installed software, users across fleet

Example requests:

• "Get running processes from sensor X"
• "List all files in C:\Windows\Temp on compromised hosts"
• "Get OS version from all Windows servers when they come online"
• "Run a memory collection on all hosts tagged 'incident-response'"
• "Execute netstat on all online Linux servers"

Core Concepts

Challenge 1: Offline Agents

Direct tasking (getprocesses, dirlist, etc.) only works for online sensors. If a sensor is offline, the task fails immediately.

Reliable tasking queues tasks for delivery when sensors come online. Tasks persist for a configurable TTL (default: 1 week).

Challenge 2: Receiving Responses

Decision Tree

START: User wants to task sensors
    |
    v
Are all targets online AND ≤5 sensors?
    |
    |--YES--> Use Direct Tasking (inline response, parallel execution)
    |
    |--NO--> Use Reliable Tasking (>5 sensors OR any offline)
              |
              v
       Do you need the response data?
              |
              |--NO (action-only like isolate)--> Create Reliable Task, done
              |
              |--YES--> Do you need automated handling?
                        |
                        |--NO--> Create Reliable Task, wait 2+ min, then LCQL query
                        |
                        |--YES--> 1. Create D&R rule with TTL FIRST
                                  2. THEN create Reliable Task
                                  (rule must exist before task to avoid missing responses)

How to Use

Step 1: Understand the Request

Parse the user's request to determine:

• Target scope: Single sensor, selector, all sensors?
• Task type: Data collection (needs response) or action (unidirectional)?
• Urgency: Need immediate response or can wait?
• Response handling: Inline, LCQL collection, or automated D&R?

Step 2: Get Organization and Sensors

If you don't have the OID, get it first:

limacharlie org list --output yaml

Check sensor status if targeting specific sensors:

limacharlie sensor get --sid <sid> --oid <oid> --output yaml

CRITICAL: Filter to Taskable EDR Sensors

Before spawning executor agents or tasking sensors, you MUST verify sensors are EDR agents (not adapters or cloud sensors).
Non-EDR sensors will fail with UNSUPPORTEDFORPLATFORM.

Taskable sensors require BOTH:
- Platform: windows, linux, macos, or chrome
- Architecture: NOT usp_adapter (code 9)

A sensor running on Linux platform but with arch=usp_adapter is an adapter (USP), not an EDR agent. These adapters forward logs but cannot execute commands.

Use combined selector when listing sensors:
```bash
limacharlie sensor list --selector "(plat==windows or plat==linux or plat==macos) and arch!=usp_adapter" --online --oid <oid> --output yaml
```

Or check sensor info before tasking - verify both platform is in ["windows", "linux", "macos", "chrome"] AND arch is not 9 / usp_adapter.

Step 3A: Direct Tasking (≤5 Online Sensors)

For immediate data collection from a small number of online sensors (up to 5), use direct tasking functions with parallel execution.

Available Direct Task Commands (return response inline via limacharlie task send --sid <sid> --task <command>):

Example - Get processes from a sensor:

limacharlie task send --sid <sid> --task os_processes --oid <oid> --output yaml

Step 3B: Reliable Tasking (>5 Sensors or Offline)

For more than 5 sensors, offline sensors, or fleet-wide operations, use reliable tasking.

IMPORTANT: Order of Operations

If you need automated response handling via D&R rules, you MUST create the D&R rule FIRST, before creating the reliable task. This ensures no responses are missed between task creation and rule deployment.

Order: D&R Rule → Reliable Task (not the other way around)

Create a reliable task:

# reliable-send is per-sensor; first list matching sensors, then loop
limacharlie sensor list --selector 'plat==windows' --oid <oid> --filter '[].sid' --output yaml

for sid in <sid-list>; do
  limacharlie task reliable-send --sid $sid --command 'os_version' --investigation-id 'fleet-inventory-2024-01' --ttl 86400 --oid <oid> --output yaml
done

Key Parameters:

• --sid: Target sensor ID (reliable-send operates per-sensor)
• --command: The command to execute (e.g., osversion, memmap --pid 4, run --shell-command whoami)
• --investigation-id: Identifier that appears in routing/investigation_id of responses (for collection)
• --ttl: Time-to-live in seconds (default: 604800 = 1 week)

Available Task Commands:

Any sensor command can be used as a task. Common ones:

Step 4: Collecting Responses

Option A: LCQL Query (Manual Collection)

After reliable tasking, wait at least 2 minutes for responses to arrive, then query:

First, generate the LCQL query:

limacharlie ai generate-query --prompt "Find all events in the last 2 hours where investigation_id contains 'fleet-inventory-2024-01'" --oid <oid> --output yaml

Then run the query:

limacharlie search run --query "<generated_query>" --start <ts> --end <ts> --oid <oid> --output yaml

Option B: D&R Rule (Automated Handling)

For automated response handling, create a D&R rule that matches the investigation_id.

CRITICAL: Create the D&R rule BEFORE creating the reliable task. Online sensors may respond within milliseconds - if the rule doesn't exist yet, those responses will be missed.

Step 1: Generate the detection:

limacharlie ai generate-detection --description "Match events where investigation_id contains 'fleet-inventory-2024-01'" --oid <oid> --output yaml

Step 2: Generate the response:

limacharlie ai generate-response --description "Report to output 'siem' and add detection 'FLEET_INVENTORY_RESPONSE'" --oid <oid> --output yaml

Step 3: Write to temp files and validate:

cat > /tmp/detect.yaml << 'EOF'
<detection_yaml>
EOF
cat > /tmp/respond.yaml << 'EOF'
<response_yaml>
EOF
limacharlie dr validate --detect /tmp/detect.yaml --respond /tmp/respond.yaml --oid <oid>

Step 4: Deploy with expiry:

Calculate expiry timestamp (e.g., 7 days from now):

date -d '+7 days' +%s

cat > /tmp/rule.yaml << 'EOF'
detect:
  <detection_yaml>
respond:
  <response_yaml>
EOF
limacharlie dr set --key temp-fleet-inventory-handler --input-file /tmp/rule.yaml --oid <oid>

Step 5: NOW create the reliable task

Only after the D&R rule is deployed, create the reliable task (see Step 3B above). The rule will catch all responses as sensors execute the task.

Monitoring Reliable Tasks

List pending tasks for a sensor:

limacharlie task reliable-list --sid <sensor-id> --oid <oid> --output yaml

Delete/cancel a task:

limacharlie task reliable-delete --sid <sensor-id> --task-id <task_id> --oid <oid>

Example Workflows

Example 1: Get Processes from Single Sensor

User: "Get running processes from sensor abc-123"

# Check sensor status
limacharlie sensor get --sid abc-123 --oid c7e8f940-... --output yaml

# If online, get processes directly
limacharlie task send --sid abc-123 --task os_processes --oid c7e8f940-... --output yaml

Example 2: Fleet-Wide OS Inventory

User: "Get OS version from all Windows servers when they come online"

# List Windows sensors first
limacharlie sensor list --selector 'plat == windows' --oid c7e8f940-... --filter '[].sid' --output yaml

# Create reliable task per sensor (loop over SIDs)
for sid in <sid-list>; do
  limacharlie task reliable-send --sid $sid --command 'os_version' --investigation-id 'os-inventory-20240120' --oid c7e8f940-... --output yaml
done

Response to user: "Created reliable tasks to collect OS version from all Windows sensors.

• Online sensors will execute immediately
• Offline sensors will execute when they reconnect
• Task will remain active for 1 week (default TTL)
• Use investigation ID 'os-inventory-20240120' to query responses via LCQL"

Example 3: Incident Response Collection

User: "Run memory collection on all hosts tagged 'incident-response', I need the data sent to our SIEM"

# Step 1: Create D&R rule FIRST to forward responses to SIEM
# Use AI generation for the detection and response, then deploy:
limacharlie ai generate-detection --description "Match events where investigation_id contains 'ir-memcollect-001'" --oid c7e8f940-... --output yaml
limacharlie ai generate-response --description "Report to output 'siem' and add detection 'IR_MEMCOLLECT_RESPONSE'" --oid c7e8f940-... --output yaml
# Write generated YAML to files, validate, then deploy:
limacharlie dr validate --detect /tmp/detect.yaml --respond /tmp/respond.yaml --oid c7e8f940-... --output yaml
# Combine into single rule file with detect/respond keys, then set:
limacharlie dr set --key temp-ir-memcollect-handler --input-file /tmp/ir-rule.yaml --oid c7e8f940-...

# Step 2: Get sensors tagged 'incident-response'
limacharlie sensor list --tag incident-response --oid c7e8f940-... --filter '[].sid' --output yaml

# Step 3: THEN create reliable task per sensor (rule is now in place to catch responses)
for sid in <sid-list>; do
  limacharlie task reliable-send \
    --sid $sid \
    --command 'mem_map --pid 4' \
    --investigation-id 'ir-memcollect-001' \
    --ttl 172800 \
    --oid c7e8f940-... --output yaml
done

Example 4: Quick Data Collection with Inline Response

User: "What's the OS version on all 5 of our production Linux servers?"

If sensors are online and small in number, parallel direct tasking is faster:

# Run parallel tasks for each sensor
limacharlie task send --sid sid1 --task os_version --oid <oid> --output yaml &
limacharlie task send --sid sid2 --task os_version --oid <oid> --output yaml &
limacharlie task send --sid sid3 --task os_version --oid <oid> --output yaml &
limacharlie task send --sid sid4 --task os_version --oid <oid> --output yaml &
limacharlie task send --sid sid5 --task os_version --oid <oid> --output yaml &
wait

Important Notes

Taskable Sensors (EDR Only)

WARNING: Sensor tasking only works for EDR agents (real endpoint agents). Cloud sensors, adapters, and USP log sources cannot receive tasks.

Taskable sensors require BOTH conditions:

1. Platform is Windows, Linux, macOS, or Chrome
2. Architecture is NOT usp_adapter (code 9)

Platforms that support tasking:

Non-taskable sensors include:

• Cloud sensors (Office365, Okta, AWS, GCP, Azure, etc.)
• External adapters (ext-* sensors like ext-zeek, ext-strelka)
• USP log sources (Syslog, S3 buckets, webhooks)
• Any sensor with arch=usp_adapter (architecture code 9) - even if platform is Linux/macOS

These sensors will return UNSUPPORTEDFORPLATFORM errors when tasked.

Recommendation: When tasking a fleet, filter by both platform AND architecture:

• Use combined selector: (plat==windows or plat==linux or plat==macos) and arch!=usp_adapter
• Or check sensor info for both platform and arch fields before direct tasking

Extension Requirement

Reliable tasking requires the ext-reliable-tasking extension to be subscribed in the organization. If you get a 403 error, the extension may not be enabled.

Selector Syntax

Selectors use bexpr syntax:

• plat==windows - Windows sensors
• plat==linux - Linux sensors
• production in tags - Sensors with 'production' tag
• hostname matches '^web-' - Hostname starts with 'web-'
• sid=='abc-123-def-456' - Specific sensor
• * - All sensors

Context for Response Collection

The context parameter in reliable tasking:

• Appears in routing/investigation_id of response events
• Use unique identifiers (include date/time)
• Can be used in LCQL queries or D&R rules for matching

Timestamps

When setting TTL or expiry:

• Use bash for timestamp calculation: date -d '+7 days' +%s
• TTL is in seconds from now
• D&R rule expiry is absolute Unix timestamp

Related Skills

• detection-engineering - For creating D&R rules to handle responses
• sensor-health - For checking sensor online status across fleet
• sensor-coverage - For understanding fleet coverage before tasking

Reference

• ext-reliable-tasking documentation
• Use limacharlie task --ai-help for CLI help