Andy Robbins Profile picture
Feb 20, 2019 7 tweets 3 min read Read on X
1/n Domain trust boundaries are not, of course, security boundaries; however many organizations effectively treat them as such. #BloodHound's attack graph tells the real story of how isolated our domains are from each other. Take this simple 3-domain forest for example.
2/n The domain trust map is pretty simple. Domain 1 is trusted by Domain 2, and Domain 2 is trusted by Domain 3. (This is real, anonymized data). So principals in Domain 1 can query Domain 2 or 3 for information, but no privileges are implied by default. Image
3/n With #BloodHound we can easily find the shortest attack paths from "Domain Users" in Domain 1 to "Domain Admins" in Domain 3. Pretty easy attack path, and very common situation in the real world: Image
4/n With some Cypher, we can find every "bridge" between each domain. Here, I'm seeing how many users in "Domain 1" have admin rights on computers in "Domain 2". Image
5/n We can increase our scope and build a matrix of all these cross-domain "bridges" to see where our biggest issues are. We have [n,m], where "n" is the number of users from the domain column, and "m" is the number of computers in the domain row those users have admin rights on Image
6/n To make this data a little easier to digest, we can visualize it as a Sankey diagram (a Chord diagram would also be cool to see). Image
7/7 Don't treat domain trust boundaries as security boundaries? Good! But if you must (re-architecting a decade old forest is very expensive work), you can use this methodology to find those hidden doors between your domains. We will show you how in March.

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More from @_wald0

Feb 17, 2023
This week I added 5 new functions to #BARK. A quick thread explaining each one with examples:
Get-ServicePrincipalOwner

List the current owner(s) of a specified #Azure AD Service Principal.

Example:
New-ServicePrincipalOwner

Add a new owner to an AAD Service Principal. Owners can add credentials to SPs and then auth as them.

Example:
Read 8 tweets
Feb 16, 2023
Azure App Service Web Apps are yet another #Azure service that supports managed identity assignments.

Here's how attackers can use #BARK to abuse those assignments: Image
There are at least 3 ways to achieve code execution on an Azure App Service Web App ("Azure Web App" from here on) instance:

1. The Kudu shell execution API endpoints
2. Poison deployment to include a web shell in the app
3. Find a cmd execution vulnerability in the deployed app
We'll focus on #1 - abusing the built-in Kudu shell execution endpoints.

This is the feature the Azure GUI uses as its "Debug Console" and is documented here: github.com/projectkudu/ku…

@kfosaaen discussed this in his August 2020 blog post here: netspi.com/blog/technical… Image
Read 9 tweets
Feb 4, 2023
Interest check: should I continue developing this research? Read my notes here and please let me know if you think this is worth pursuing further.

Problem: attackers have been moving their C2 channels to legitimate services to evade detection, slip through block lists, etc.
Examples:

github.com/boku7/azureOut…
3xpl01tc0d3r.blogspot.com/2020/03/introd…

Defenders and vendors have to play catch-up whenever one of these novel C2 methods becomes popular.
I believe it's possible to proactively, semi-automatically discover these methods in existing and emerging cloud services. We can assess their attractiveness to attackers, vendors can make them less attractive and prioritize their own detection efforts.

How?
Read 15 tweets
Sep 20, 2022
#Azure Managed Identity assignments are "secure by default."

Dangerous attack paths can emerge around these assignments.

Here's those attack paths emerge, how attackers abuse them, and how defenders can eliminate them: 🧵
First we should understand what Managed Identities are. I think the best way is to understand the problem they are designed to solve.

We have a great recent example of this problem from the alleged Uber breach, where a PowerShell script may have been storing plain text creds:
This problem is not new and not surprising to many people:
Read 25 tweets
Sep 13, 2022
Tiered Administration is among the strongest security controls that exist.

But the vast majority of organizations do not use it.

Here is how you can get started using Tiered Administration TODAY in your #Azure environments: 🧵
First, understand the problem we are trying to solve with Tiered Administration:

Tiered Administration protects your most privileged assets from compromise in the event that less privileged assets are compromised.

It's the wombo combo of least privilege and defense in depth.
Do Tiered Administration effectively and you DRAMATICALLY reduce risks posed by ransomware actors, insider threats, etc.

Most efforts get stuck in the very first step: identifying which assets go into which tiers.

Here's how you do this:
Read 11 tweets
Aug 25, 2022
How to prevent Kerberoasting:

Kerberoasting is an incredibly powerful and reliable attack against Active Directory. In some situations it can result in an attacker becoming Domain Admin nearly instantaneously.

Here's how to prevent this attack: 🧵 Image
First we need to identify Active Directory users that are "kerberoastable" - possible targets for the attacker to choose to Kerberoast.

Kerberoast relies on a user having some value in their "serviceprincipalnames" attribute.

Find all of them instantly with no 3rd party tools:
dsquery has been built in to Windows Server since Server 2008. You also get it when installing RSAT.

Here's the command:

dsquery * "dc=contoso,dc=com" -filter "(&(objectcategory=user)(servicePrincipalName=*))" -attr distinguishedName servicePrincipalName
Read 12 tweets

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