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Try Falco on Kubernetes

Learn how to deploy Falco on Kubernetes

First, ensure you can access a test Kubernetes cluster running with Linux nodes, either x86_64 or ARM64. Note that using Docker Desktop on Windows or macOS will not work for this purpose. Also, you will need to have kubectl and helm installed and configured.

Deploy Falco

First, install the helm repository:

helm repo add falcosecurity https://falcosecurity.github.io/charts
helm repo update

Then install Falco:

helm install --replace falco --namespace falco --create-namespace --set tty=true falcosecurity/falco

And check that the Falco pods are running:

kubectl get pods -n falco

Falco pod(s) might need a few seconds to start. Wait until they are ready:

kubectl wait pods --for=condition=Ready --all -n falco

Falco comes with a pre-installed set of rules that alert you upon suspicious behavior.

Trigger a rule

Let's create a deployment:

kubectl create deployment nginx --image=nginx

And execute a command that would trigger a rule:

kubectl exec -it $(kubectl get pods --selector=app=nginx -o name) -- cat /etc/shadow

Now let's take a look at the Falco logs:

kubectl logs -l app.kubernetes.io/name=falco -n falco -c falco | grep Warning

You will see logs for all the Falco pods deployed on the system. The Falco pod corresponding to the node in which our nginx deployment is running has detected the event, and you'll be able to read a line like:

09:46:05.727801343: Warning Sensitive file opened for reading by non-trusted program (file=/etc/shadow gparent=systemd ggparent=<NA> gggparent=<NA> evt_type=openat user=root user_uid=0 user_loginuid=-1 process=cat proc_exepath=/usr/bin/cat parent=containerd-shim command=cat /etc/shadow terminal=34816 container_id=bf74f1749e23 container_image=docker.io/library/nginx container_image_tag=latest container_name=nginx k8s_ns=default k8s_pod_name=nginx-7854ff8877-h97p4)

This is your first Falco event 🦅! If you are curious, this is the rule that describes it.

Create a custom rule

Now it's time to create our own rule and load it into Falco. We can be pretty creative with them, but let's stick with something simple. This time, we want to be alerted when any file is opened for writing in the /etc directory, either on the host or inside containers.

Create a file and call it falco_custom_rules_cm.yaml with the following content:

customRules:
  custom-rules.yaml: |-
    - rule: Write below etc
      desc: An attempt to write to /etc directory
      condition: >
        (evt.type in (open,openat,openat2) and evt.is_open_write=true and fd.typechar='f' and fd.num>=0)
        and fd.name startswith /etc
      output: "File below /etc opened for writing (file=%fd.name pcmdline=%proc.pcmdline gparent=%proc.aname[2] ggparent=%proc.aname[3] gggparent=%proc.aname[4] evt_type=%evt.type user=%user.name user_uid=%user.uid user_loginuid=%user.loginuid process=%proc.name proc_exepath=%proc.exepath parent=%proc.pname command=%proc.cmdline terminal=%proc.tty %container.info)"
      priority: WARNING
      tags: [filesystem, mitre_persistence]

And load it into Falco:

helm upgrade --namespace falco falco falcosecurity/falco --set tty=true -f falco_custom_rules_cm.yaml

Falco pod(s) might need a few seconds to restart. Wait until they are ready:

kubectl wait pods --for=condition=Ready --all -n falco

Then trigger our new rule:

kubectl exec -it $(kubectl get pods --selector=app=nginx -o name) -- touch /etc/test_file_for_falco_rule

And look at the logs:

kubectl logs -l app.kubernetes.io/name=falco -n falco -c falco | grep Warning

You should see a log entry like the one below:

13:14:27.811647863: Warning File below /etc opened for writing (file=/etc/test_file_for_falco_rule pcmdline=containerd-shim -namespace k8s.io -id d5438fedb274ac82963d99987313dae8da512236ace2f70472a772d95090b607 -address /run/containerd/containerd.sock gparent=systemd ggparent=<NA> gggparent=<NA> evt_type=openat user=root user_uid=0 user_loginuid=-1 process=touch proc_exepath=/usr/bin/touch parent=containerd-shim command=touch /etc/test_file_for_falco_rule terminal=34816 container_id=bf74f1749e23 container_image=docker.io/library/nginx container_image_tag=latest container_name=nginx k8s_ns=default k8s_pod_name=nginx-7854ff8877-h97p4)

Deploy Falcosidekick and Falcosidekick UI

In the previous step we displayed the rule output by examining the Falco log for the pod in the cluster that is running on the node. Now we will see how we can forward these alerts to a custom location or display them in a clean GUI. There are many ways to accomplish this but one is by using Falcosidekick which can easily be deployed with the same Helm chart.

Install Falcosidekick and Falcosidekick-UI in your test cluster:

helm upgrade --namespace falco falco falcosecurity/falco -f falco_custom_rules_cm.yaml --set falcosidekick.enabled=true --set falcosidekick.webui.enabled=true

Now check that it is running and its service is set up:

kubectl -n falco get svc

You should see something like this:

NAME                     TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
falco-falcosidekick      ClusterIP   10.43.212.119   <none>        2801/TCP   61s
falco-falcosidekick-ui   ClusterIP   10.43.35.87     <none>        2802/TCP   60s

Display events in the Falcosidekick UI

Forward the UI port, which is 2802:

kubectl -n falco port-forward svc/falco-falcosidekick-ui 2802

And point your browser to http://localhost:2802 . The default username and password are admin / admin.

Now click on "Events" on top of the page and trigger an event again:

kubectl exec -it $(kubectl get pods --selector=app=nginx -o name) -- cat /etc/shadow

You should see an event appearing in the Falcosidekick UI

Falcosidekick Event

The Falcosidekick UI can be used to quickly display events but most likely on a production system you will want to forward events to a centralized location. Falcosidekick supports more than 60 integrations. You can find an example below but you can refer to the forwarding documentation to learn more.

Forward events to a Slack webhook

Deploy Falco again, this time disabling the web UI and enabling Slack forwarding. Of course, you can enable both if you wish.

helm upgrade --namespace falco falco falcosecurity/falco \
  --set falcosidekick.enabled=true \
  --set falcosidekick.config.slack.webhookurl=YOUR_WEBHOOK_URL_HERE \
  --set falcosidekick.config.slack.minimumpriority=notice

If Slack is configured correctly, when an event is triggered you should receive a message like the following:

Slack output

Cleanup

If you wish to remove Falco from your cluster you can simply run:

helm -n falco uninstall falco