Splunk & CIS Top 20 Security Monitoring

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The purpose of this blog is to provide a quick overview on one can exploit Splunk and the Centre for Internet Security Critical Security Controls for Effective Cyber Defence best practises, otherwise known as CIS top 20.  The best practises consist of 20 key security controls (CSC), that an organisation could use to block or mitigate cyber-attacks and improve their security posture overall. The CIS CSC are ranked in order of overall importance and application to a corporate security strategy. For example, the first two controls, surrounding known inventory, are at the top of the list and are foundational in nature, ranking “very high” for attack mitigation.

The published top 20 controls are as follows:
CSC 1: Inventory of Authorized and Unauthorized Devices
CSC 2: Inventory of Authorized and Unauthorized Software
CSC 3: Secure Configurations for Hardware and Software on Mobile Devices, Laptops, Workstations, and Servers
CSC 4: Continuous Vulnerability Assessment and Remediation
CSC 5: Controlled Use of Administrative Privileges
CSC 6: Maintenance, Monitoring, and Analysis of Audit Logs
CSC 7: Email and Web Browser Protections
CSC 8: Malware Defences
CSC 9: Limitation and Control of Network Ports, Protocols, and Services
CSC 10: Data Recovery Capability
CSC 11: Secure Configurations for Network Devices such as Firewalls, Routers, and Switches
CSC 12: Boundary Defence
CSC 13: Data Protection
CSC 14: Controlled Access Based on the Need to Know
CSC 15: Wireless Access Control
CSC 16: Account Monitoring and Control
CSC 17: Security Skills Assessment and Appropriate Training to Fill Gaps
CSC 18: Application Software Security
CSC 19: Incident Response and Management
CSC 20: Penetration Tests and Red Team Exercises

  • Splunk software can be used to build and operate security operations centres of any size
  • Support the full range of information security operations, including posture assessment, monitoring, alert and incident handling, CSIRT, breach analysis and response, and event correlation
  • Out-of-the-box support for SIEM and security use cases
  • Detect known and unknown threats, investigate threats, determine compliance and use advanced security analytics for detailed insight
  • Proven integrated, big data-based security intelligence platform
  • Use ad hoc searches for advanced breach analysis
  • On-premises, cloud, and hybrid on-premises and cloud deployment options
  • Improve operational efficiency with automated and human-assisted decisions by using Splunk as a security nerve centre
  • Indexes data from any machine data source
  • Searches through machine data from a centralized console
  • Allows the security professional to add tags, create event types and correlate the incoming data with business context
  • Proactively monitors and alerts on security incidents, with automatic remediation of security issues – for example, changing a firewall rule in response to Splunk search results
  • Allows for the creation of reports, dashboards and other forms of analytics to communicate security information throughout the organization

So How Can Splunk Help?
Splunk has a free App that one can use to help provide security compliance, this is based on the CIS top 20 security controls as published by the Centre for Internet Security (CIS).

https://splunkbase.splunk.com/app/3064/

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The app provides a data-agnostic framework which exploits Splunk’s data analytics features and functions such as data model, otherwise known as the Common information model (CIM). This features allows Splunk to be data-agnostic as it normalises data for common fields, such as source IP, user etc.

The App has been developed for anyone in the IT security segment, and Splunk Administrators. It relies on data being ingested into Splunk, this would be as part of the Splunk design and assessment process, such as identifying which sources of data should be ingested, example being Windows Active Directory Logs, Firewall Logs and so forth.
Once this data has been ingested and its CIM compliant, the app runs searches and populates the dashboards for CIS compliancy, this will provide Security teams with insights as to their compliancy status and improve their overall security posture.
There are hundreds of free Splunk TA’s (Splunk Technical Add-ons), these provide field extractions, lookups, tags, and event-types, these all help the Splunk CIS app for presenting the data.

If any customisation is required, lookup files and TA’s can be developed for any application that is required for CIS compliancy.

Splunk supports the controls in four ways:

Verification:
As Splunk software ingests data, it can generate reports and dashboards that show compliance or non-compliance with controls. Incidents of non-compliance can generate alerts to SOC personnel.

Execution:
In the case of an attack or non-compliance, Splunk software can carry out recommended actions to meet controls. With version 6.0 of the CIS CSC, Splunk software becomes even more critical, since control 14 surrounding audit logs has been promoted to position

Verification & Execution:
Data from third-party sources can be correlated with data ingested in Splunk software to meet the control.

Support:
The Splunk platform provides flexible features that help security professionals with controls that are largely policy and process based.

Mapping Example – CSC 5

Controlled use of admin privileges can be accomplished with a number of toolsets that restrict the use of administrative accounts. The simplest methods are OS-level tools, like sudo, and controls that can be put in place with vendor-supplied tools like Active Directory, so with this in mind you want to comply with CSC 5: Controlled Use of Administrative Privileges to your IT environment.
Splunk can help by consuming authentication logs from across the technology environment that detail account activity, including how accounts are being accessed and from where. Authentication logs come from, but are not limited to: host devices, domain controllers, directory servers, network devices, application logs and many others. All of this data will be ingested into Splunk software for searching and correlation.
Any use of known administrative accounts like “Administrator” and “root” and “sa” can easily be searched across the entire environment and reported or alerted upon.
The below is an example of a dashboard showing Successful Logins from 10 Most Rare Users – Privileged Accounts

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So, Get Splunking, and the CIS App if you need to implement the CIS CSC, Splunk makes all data in your organization security relevant, as data is indexed by Splunk Enterprise, it becomes instantly searchable and security professionals can easily correlate all of these seemingly disparate data sources. Furthermore, the different data types can be seen in the context of data locked in business systems, which is often the key factor in determining correct root causes. Security professionals can then build dashboards and reports on top of the data, and set up actions and alerts to be executed on specific thresholds. In addition, any analysis can be operationalized to proactively protect your organization from an emerging threat.

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