harmj0y

The PowerView PowerUsage Series #3

Published September 19, 2017 by harmj0y

This is the third post in my “PowerView PowerUsage” series, and follows the same Scenario/Solution/Explanation pattern as the previous entries. The original post contains a constantly updated list of the entire series. Active Directory access control is something my workmates and I have been very interested in over the past year. So far, this has resulted in the release of BloodHound’s ACL Attack Path Update, as well as work on Active Directory DACL backdooring by @_wald0 and myself (whitepaper here). This post will cover DACL enumeration for GPOs in a foreign domain. Why care about this? Well, if you are…

Hunting With Active Directory Replication Metadata

Published September 6, 2017 by harmj0y

With the recent release of BloodHound’s ACL Attack Path Update as well as the work on Active Directory DACL backdooring by @_wald0 and myself (whitepaper here), I started to investigate ACL-based attack paths from a defensive perspective. Sean Metcalf has done some great work concerning Active Directory threat hunting (see his 2017 BSides Charm “Detecting the Elusive: Active Directory Threat Hunting” presentation) and I wanted to show how replication metadata can help in detecting this type of malicious activity. Also, after this post had been drafted, Grégory LUCAND pointed out to me the extensive article (in French) he authored on…

The PowerView PowerUsage Series #2

Published August 16, 2017 by harmj0y

This is the second post in my “PowerView PowerUsage” series. The original post contains a constantly updated list of the entire series. This post will follow the same scenario/solution/explanation format, and is definitely a bit simpler than the first post. The Scenario While on an engagement in a multi-domain forest, you end up with a number of computer “short names” (like WINDOWS1) in a file computers.txt that you want to resolve to complete DNS host names. The Solution The Explanation This one’s fairly straight-forward. We use gc (Get-Content) to output the list of computer shortnames, piping it to Sort-Object -Unique…

Offensive Encrypted Data Storage (DPAPI edition)

Published July 31, 2017 by harmj0y

Last September I wrote a post titled “Offensive Encrypted Data Storage” that detailed an approach to securely storing data on disk during offensive engagements. I recently revisited the idea a bit while once again thinking about disk artifacts, and remembered about DPAPI. The Windows Data Protection API (DPAPI) provides a simplified set of cryptographic functions that abstracts away concerns about deriving/storing keys, and removes the need to include additional libraries to use this functionality. DPAPI uses either the user’s current logon credential or the the randomized machine account password (depending on the “scope” passed to the functions) to protect, by…

The PowerView PowerUsage Series #1

Published July 17, 2017 by harmj0y

PowerView is probably my favorite bit of code I’ve written, and definitely the one I most regularly use (as evidenced by my recent posts). My team also heavily utilizes the toolkit, and we’ve come up with some cool uses for it over the past several years. For a long time I’ve wanted to share some of the real “power” uses of PowerView, like the PowerView “tricks” highlighted here. My intention for this series is to demonstrate how you can use PowerView to solve interesting problems and the thought process we put behind each solution. These posts should be short-and-sweet, less…

A Three Year Retrospective

Published May 24, 2017 by harmj0y

I love blogging. One of my favorite parts of my job is figuring out details about an operationally useful topic and trying to explain it in a digestible way. I’ve found that blogging about (or teaching) a particular subject really helps solidify my knowledge, at least as I understand it at the time. It also teaches me how much I don’t know, and forces me to confront my past mistakes and misconceptions. I’ve posted 63 posts over the last three years, totalling 70k+ words of content. Some posts were relatively simplistic, some were update notes for various projects, but I…

Pass-the-Hash Is Dead: Long Live LocalAccountTokenFilterPolicy

Published March 16, 2017 by harmj0y

Nearly three years ago, I wrote a post named “Pass-the-Hash is Dead: Long Live Pass-the-Hash” that detailed some operational implications of Microsoft’s KB2871997 patch. A specific sentence in the security advisory, “Changes to this feature include: prevent network logon and remote interactive logon to domain-joined machine using local accounts…” led me to believe (for the last 3 years) that the patch modified Windows 7 and Server 2008 behavior to prevent the ability to pass-the-hash with non-RID 500 local administrator accounts. My colleague Lee Christensen recently pointed out that this was actually incorrect, despite Microsoft’s wording, and that the situation is…

Targeted Kerberoasting

Published January 19, 2017 by harmj0y

This is a short followup demonstrating a technique that dawned on me after posting about decrypting AS-REPs earlier this week. As mentioned previously, @_wald0, @cptjesus, and I are currently working Active Directory ACL integration for BloodHound. One of the control relationships we’re interested in is GenericAll/GenericWrite over a target user object, say victimuser in this instance. If we want to utilize the user’s access, we could force a password reset, but this is fairly ‘destructive’ in that the target user would notice. We’ve been brainstorming another method to abuse these types of relationships with the target remaining unaware, and we…

Roasting AS-REPs

Published January 17, 2017 by harmj0y

Last November, I published a post titled “Kerberoasting Without Mimikatz” that detailed new developments with PowerView and Tim Medin‘s Kerberoasting attack. This started me down the path of looking at Kerberos just a bit more closely. Then a few weeks ago, my coworker Lee Christensen found an interesting presentation from Geoff Janjua of Exumbra Operations titled “Kerberos Party Tricks: Weaponizing Kerberos Protocol Flaws“, slides and toolkit located here. One of the interesting points that Geoff mentioned, and that his Python-based “Party Trick” toolkit executes, was abusing user accounts that don’t require Kerberos preauthentication. I recently dove much deeper into this…

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