Execution: Possible Remote Command Execution Detected

This document describes a threat finding type in Security Command Center. Threat findings are generated by threat detectors when they detect a potential threat in your cloud resources. For a full list of available threat findings, see Threat findings index.

Overview

A process was detected spawning common UNIX commands via a network socket, potentially emulating a reverse shell. This behavior suggests an attempt to establish unauthorized remote access to the system, granting the attacker the ability to execute arbitrary commands as if they were directly interacting with the compromised machine. Adversaries frequently utilize reverse shells to bypass firewall restrictions and gain persistent control over a target. The detection of command execution initiated through a socket signifies a significant security risk, as it allows for a wide range of malicious activities, including data exfiltration, lateral movement, and further exploitation, making this a critical finding that demands immediate investigation to identify the source of the connection and the actions performed.

How to respond

To respond to this finding, do the following:

Step 1: Review finding details

  1. Open an Execution: Possible Remote Command Execution Detected finding as directed in Reviewing findings. The details panel for the finding opens to the Summary tab.

  2. On the Summary tab, review the information in the following sections:

    • What was detected, especially the following fields:
      • Program binary: the absolute path of the executed binary.
      • Arguments: the arguments passed during binary execution.
    • Affected resource, especially the following fields:
      • Resource full name: the full resource name of the cluster including the project number, location, and cluster name.

  3. In the detail view of the finding, click the JSON tab.

  4. In the JSON, note the following fields.

    • resource:
      • project_display_name: the name of the project that contains the cluster.
    • finding:
      • processes:
      • binary:
        • path: the full path of the executed binary.
      • args: the arguments that were provided while executing the binary.
    • sourceProperties:
      • Pod_Namespace: the name of the Pod's Kubernetes namespace.
      • Pod_Name: the name of the GKE Pod.
      • Container_Name: the name of the affected container.
      • Container_Image_Uri: the name of the container image being deployed.
      • VM_Instance_Name: the name of the GKE node where the Pod executed.

  5. Identify other findings that occurred at a similar time for this container. Related findings might indicate that this activity was malicious, instead of a failure to follow best practices.

Step 2: Review cluster and node

  1. In the Google Cloud console, go to the Kubernetes clusters page.

    Go to Kubernetes clusters

  2. On the Google Cloud console toolbar, select the project listed in resource.project_display_name, if necessary.

  3. Select the cluster listed on the Resource full name row in the Summary tab of the finding details. Note any metadata about the cluster and its owner.

  4. Click the Nodes tab. Select the node listed in VM_Instance_Name.

  5. Click the Details tab and note the container.googleapis.com/instance_id annotation.

Step 3: Review Pod

  1. In the Google Cloud console, go to the Kubernetes Workloads page.

    Go to Kubernetes Workloads

  2. On the Google Cloud console toolbar, select the project listed in resource.project_display_name, if necessary.

  3. Filter on the cluster listed on the Resource full name row in the Summary tab of the finding details and the Pod namespace listed in Pod_Namespace, if necessary.

  4. Select the Pod listed in Pod_Name. Note any metadata about the Pod and its owner.

Step 4: Check logs

  1. In the Google Cloud console, go to Logs Explorer.

    Go to Logs Explorer

  2. On the Google Cloud console toolbar, select the project listed in resource.project_display_name, if necessary.

  3. Set Select time range to the period of interest.

  4. On the page that loads, do the following:

    1. Find Pod logs for Pod_Name by using the following filter:
      • resource.type="k8s_container"
      • resource.labels.project_id="RESOURCE.PROJECT_DISPLAY_NAME"
      • resource.labels.location="LOCATION"
      • resource.labels.cluster_name="CLUSTER_NAME"
      • resource.labels.namespace_name="POD_NAMESPACE"
      • resource.labels.pod_name="POD_NAME"
    2. Find cluster audit logs by using the following filter:
      • logName="projects/RESOURCE.PROJECT_DISPLAY_NAME/logs/cloudaudit.googleapis.com%2Factivity"
      • resource.type="k8s_cluster"
      • resource.labels.project_id="RESOURCE.PROJECT_DISPLAY_NAME"
      • resource.labels.location="LOCATION"
      • resource.labels.cluster_name="CLUSTER_NAME"
      • POD_NAME
    3. Find GKE node console logs by using the following filter:
      • resource.type="gce_instance"
      • resource.labels.instance_id="INSTANCE_ID"

Step 5: Investigate running container

If the container is still running, it might be possible to investigate the container environment directly.

  1. Go to the Google Cloud console.

    Open Google Cloud console

  2. On the Google Cloud console toolbar, select the project listed in resource.project_display_name, if necessary.

  3. Click Activate Cloud Shell

  4. Obtain GKE credentials for your cluster by running the following commands.

    For zonal clusters:

    gcloud container clusters get-credentials CLUSTER_NAME \
      --zone LOCATION \
      --project PROJECT_NAME

    For regional clusters:

    gcloud container clusters get-credentials CLUSTER_NAME \
      --region LOCATION \
      --project PROJECT_NAME

    Replace the following:

    • CLUSTER_NAME: the cluster listed in resource.labels.cluster_name
    • LOCATION: the location listed in resource.labels.location
    • PROJECT_NAME: the project name listed in resource.project_display_name

  5. Retrieve the executed binary:

    kubectl cp \
      POD_NAMESPACE/POD_NAME:PROCESS_BINARY_FULLPATH \
      -c CONTAINER_NAME \
      LOCAL_FILE

    Replace local_file with a local file path to store the added binary.

  6. Connect to the container environment by running the following command:

    kubectl exec \
      --namespace=POD_NAMESPACE \
      -ti POD_NAME \
      -c CONTAINER_NAME \
      -- /bin/sh

    This command requires the container to have a shell installed at /bin/sh.

Step 6: Research attack and response methods

  1. Review MITRE ATT&CK framework entries for this finding type: Command and Scripting Interpreter.
  2. To develop a response plan, combine your investigation results with MITRE research.

Step 7: Implement your response

The following response plan might be appropriate for this finding, but might also impact operations. Carefully evaluate the information you gather in your investigation to determine the best way to resolve findings.

  • Contact the owner of the project with the compromised container.
  • Stop or delete the compromised container and replace it with a new container.

What's next