Tools Deep Dive: Sigma
Recalling our conversation about the tools of the trade that will make life easier in our Cybersecurity lives, we get into another one in the toolbox. Last week, we discussed regex, and how it can greatly help in security related tasks.
Today, we're diving into another one: Sigma.
If Regex was a Swiss army knife for pattern matching, Sigma is the multi-purpose tool we didn't know we needed for security alerts 🛠️.
Unpacking Sigma
At its core, Sigma is something of a Rosetta Stone for security alerts.
Directly from Sigma’s Github README “Sigma is for log files what Snort is for network traffic and YARA is for files.” That’s a pretty good one-liner to sum it up.
It's a generic and open signature format that lets you describe relevant log events in their simplest terms.
Picture this: being able to have your security alerts into any format suitable for any tool. That's Sigma
In other words, you can take the Sigma format, apply some custom fields, and have a working ELK, Splunk search, etc.
Sigma's Impact on the Security Community
Universal Application: Sigma rules can be effortlessly converted for any SIEM, log management solution, or security tool.
Fostering Collaboration: Sigma isn't just a tool; it's a movement. It encourages the security community to share top-tier rules.
As cyber threats morph and evolve, we’re collectively better armed to tackle them. And because it’s an open format, there’s no need to fear about any “secret sauce”.
Breaking Free from Vendor Chains: Sigma ensures you’re never shackled to one specific tool. Transition between different platforms without a problem, ensuring your alert configurations remain intact.
The place where detection engineers, threat hunters and all defensive security practitioners collaborate on detection rules.
- From the Sigma Readme
If you're deep in the trenches of security, here's what Sigma's can do for you:
Simplicity at its Best: Define your parameters, set a condition, and you're good to go.
Seamless Integration: Sigma plays well with others. Integrate it with a plethora of tools to streamline your workflow.
Stay Ahead of the Curve: With the global security community actively sharing Sigma rules, you're always on top of the latest threats.
A Glimpse at Sigma Rules
Here’s a snippet of what an example rule could look like in an oversimplified example.
title: Unusual File Access
description: Detects access to sensitive documents specified in a list
logsource:
product: windows
service: sysmon
detection:
keywords:
- "Confidential.docx"
- "Unauthorized access"
condition: keywordsThis rule would be for when there's unexpected access to a confidential document on a Windows system, utilizing the Sysmon service. There would need to be a agreed upon list or lookup table beforehand of these sensitive documents. Think, a certain naming convention, data classification, etc.
Here’s an example rule from Sigma’s Github.
This rule raises a flag when there's an upload of data using the curl command. This could tip off activity of mal access to confidential documents. This could be a good Threat Hunting exercise as well.
This gives an idea of how flexible Sigma can be.
As mentioned earlier, since this is an open generic format, the rules can be shared which help others in the community along the way, with no apprehension of any internal gems getting out.
Rules, alerts, whatever you decide to call them, they are the output of your detection efforts. You can see this post for more detail on this.
Sigma vs. Regex
Just to sum this one up, Regex is focused on pattern matching for files or text. Sigma casts a wider net, concentrating on security alerts across diverse platforms.
Both are vital in our cybersecurity toolkit. They just have different applications and use cases.
Wrapping Up
Sigma is an example of what success in open source looks like. For security practitioners, it's a beacon that not only simplifies but amplifies.
Stay tuned, as we'll be going deeper into the world of Sigma in a future post. If you enjoyed this post, check out other posts in this tools series.