Programmatically filter unusual DNS Requests with Cisco Umbrella APIs
We use the Web in our on a regular basis lives to get work accomplished, handle our lives, and even socialize. We take this Web utilization with no consideration as of late, however the actuality is that we’re speaking greater than ever on a world scale, instantaneously, and infrequently, with people we’ve by no means met in-person or with third-party providers we don’t totally perceive.
From a cybersecurity perspective, this appears to be like like a whole lot of DNS visitors to have to watch, perceive, and examine. And, there are growing causes to do exactly that. After the main Colonial Pipeline ransomware assault that resulted in a $4.4 million ransom fee in 2021, the TSA issued (and has since, reissued) a safety directive to pipeline utility firms that, partially, requested them to higher perceive their DNS visitors.
After all, pipelines usually are not the one targets of such assaults, which means we want cheap methodologies for figuring out and investigating doubtlessly malicious domains. On this article, we stroll you thru the way you would possibly programmatically achieve visibility into and examine unusual DNS requests utilizing Cisco Umbrella APIs.
Preliminary developer setup
To create this automation, we assume you have got an energetic Cisco Umbrella account with API entry, Python3, and an built-in developer atmosphere (IDE) that helps Python.
Should you’re not but an Umbrella person, otherwise you’d merely wish to create a proof-of-concept (POC) round this, you’ll be able to leverage the always-on Umbrella Safe Web Gateway sandbox via Cisco DevNet.
Defining what visitors is “unusual”
The day earlier than writing this text, Cisco Umbrella processed over 800 billion DNS requests. Because of this constantly large quantity of visitors processing and evaluation, Umbrella maintains an updated “Prime 1-Million Domains” listing as a CSV. This data establishes a baseline of what visitors is widespread.
We will decide what visitors coming out of your Umbrella community is unusual by evaluating it to this Prime 1-Million Domains listing.
To do that, we make an API name utilizing the Umbrella Experiences API to retrieve the Prime Locations seen by your Umbrella community previously week. The decision returns a listing of domains from most to least widespread, one per row, as a CSV, that we will clear to take away the rank order and non-domains. (For instance, take away the 8 on this row: 8,www.google.com, and take away IP tackle locations as a result of they received’t match an Umbrella Prime 1-Million area)
We will then write logic that compares the domains seen by your community to Umbrella’s Prime 1-Million and provides any of your domains that aren’t on that listing to a brand new CSV.
Pattern Code
We’ve written a pattern Python script that can assist you obtain this utilizing your personal DNS visitors! That script, together with directions for working it, may be discovered right here.
Investigating unusual domains with Umbrella APIs
When you’ve recognized which domains seen by your community are thought of much less widespread, it’s possible you’ll select to additional examine some—or all—of them utilizing Umbrella Examine.
When you’ve got an Umbrella DNS Safety Benefit or Safe Web Gateway (SIG) package deal, within the Umbrella dashboard, you’ll be able to navigate to Examine > Good Search and seek for the area you’d like to research. You’ll see outcomes that present data wanting one thing like what you see beneath for examplemalwaredomain.com:
Determine 1: The start of Umbrella Examine outcomes for examplemalwaredomain.com
The outcomes first present you each the content material and safety classes for the area, supplied by Cisco Talos. We will see that this area is classed as malware and is already on a Malware Block Record; although, if we needed to, we might discover further data on this area throughout Talos, Google, or VirusTotal (high proper).
Determine 2: The chance rating and safety indicators for examplemalwaredomain.com
Scrolling down the outcomes, we subsequent see the chance rating assigned to this area and the safety indicators that went into calculating that rating. On this case, the area is classed as Excessive Threat, with further data on the safety indicators used right here.
After viewing fundamental data on the area, corresponding to when it was created and from what nation it originates, in addition to related observables like IP addresses, title servers, and information, you’ll discover WHOIS document data on the area (see beneath). You’ll discover that Umbrella Examine permits you to additional examine the related e-mail tackle and nameservers.
Determine 3: WHOIS document knowledge for examplemalwaredomain.com
Lastly, we will view a world map displaying the place DNS requests to examplemalwaredomain.com. Within the instance map beneath, over 95% of DNS requests to this area originate from the USA.
Determine 4: International requestor distribution map for examplemalwaredomain.com
These Umbrella Examine outcomes are additionally accessible as a part of the Umbrella Examine API, which means that the investigation of those unusual domains can be accomplished programmatically.
Extra alternatives for automation
What are the probabilities for constructing upon the automation we’ve supplied within the pattern code?
- Examine – including logic that for every unusual area, an API name is made to the Umbrella Examine endpoint to retrieve information and any risk intel
- Ticketing – you would combine a ticketing system, like Jira, by leveraging its API to create and assign a ticket for every unusual area
- Coverage Adjustments – use the Umbrella Locations Record API to permit or block a number of of the unusual domains
- Reporting – export the unusual domains, and maybe information on them from Umbrella Examine, right into a extra palatable format like PDF. Area information is also enhanced by intel from different safety merchandise, by viewing related gadgets and their relationships with the area utilizing JupiterOne, and/or utilized in a visualization.
- Orchestration – you’ll be able to orchestration an automation workflow with a number of steps (not all of these steps want be automated) utilizing Cisco XDR. The workflow would possibly embody all steps your group requires for investigation and incident response.
- Communication – quite than save the ensuing CSV of domains domestically, it’s possible you’ll select to mechanically e-mail the outcomes to events or submit the outcomes to a messaging platform like WebEx.
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