Securing Splunk

I feel like security is an often overlooked part of being a Splunk Engineer. This blog post is all about the importance of securing Splunk and the systems that it runs on. In addition to following the Securing Splunk guide in Splunk Docs, here are some other best practices you should be thinking about...

1. Forwarding your local system messages and audit logs to syslog and then of course to Splunk
2. Forwarding all _internal, _introspection, and _internal logs from all non-indexing instance of Splunk to your indexers
3. Configuring host-based firewall rules (e.g. IPTABLES, ufw, or firewalld) for both inbound and outbound connections, specific to port, protocol, and destination host/network(s)
4. Deploying additional open-source security tools to your core Splunk servers, such as OSQuery, OSSEC, or ClamAV
5. Splunking your bash history
6. Disabling the REST port on forwarders when it's not needed
7. Mitigating the POODLE attack in Splunk Web
8. Changing default certificates used for Splunkd, Splunk Web, etc.
9. Using encryption for Splunk to Splunk (S2S) connections
10. Hardening SSH on your Splunk servers
11. Enabling 2FA for SSH 
12. Restricting who has the admin role in Splunk to only a handful of users
13. Implementing patching and vulnerability management policies
14. Hardening the operating system of your Splunk servers using the CIS benchmarks, along with other security controls recommended by NIST, SANS, etc.
15. Enabling data integrity control on all of your indexes
16. Using a common splunk.secret file so that you can securely deploy passwords via configuration files 
17. Using different SSH key pairs for each environment and rotating them periodically
18. Securely storing passwords, secrets, API keys, and other sensitive information using tools like Vault by HashiCorp
19. Disabling Splunk Web on hosts that don't need it (think indexers and heavy forwarders)
20. Changing the default password for the admin account by deploying a user-seed.conf file
21. Using a separate account for distributed search than the admin account
22. Restricting usage of the admin account so that you can properly audit who is making changes through Splunk web or Splunk CLI
23. Enabling SSL on Splunk Web with certificates signed by a trusted CA
24. If you're an app developer, storing passwords using the KV store instead of in plain text contained in configuration files