Listing remote named pipes

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On Windows, named pipes are a form of interprocess communication (IPC) that allows processes to communicate with one another, both locally and across the network. Named pipes serve as a mechanism to transfer data between Windows components as well as third-party applications and services. Both locally as well as on a domain. From an offensive perspective, named pipes may leak some information that could be useful for reconnaissance purposes. Since named pipes can also be used (depending on configuration) to access services remotely – they could allow remote exploits (MS08-067).

In this post we will explore how named pipes can be listed remotely in offensive operations, for example via an implant running on a compromised Windows system.

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Several tools already exist to list named pipes.

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Solving The “Unhooking” Problem

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For avoiding EDR userland hooks, there are many ways to cook an egg:

Direct system calls (syscalls), Indirect syscalls, unhooking, hardware breakpoints, and bringing and loading your own version of a library. These methods each have advantages and disadvantages. When developing a C2 implant it’s nice to work with a combination of multiple of these. For instance, you could use a strong (in)direct syscall library for direct usermode to kernel transition, then use unhooking or hardware breakpoints for user mode-only (to bypass AMSI, ETW e.g.) functions.

Regarding system calls, excellent research has already been done. A small selection of relevant blog posts is Klezvirus’ post on syswhispers, MDSec’s post on direct invocation of system calls and our own blog post on combining direct system calls srdi.

So,

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Cobalt Strike and Outflank Security Tooling: Friends in Evasive Places

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This is a joint blog written by the Cobalt Strike and Outflank teams. It is also available on the Cobalt Strike site.

Over the past few months there has been increasing collaboration and knowledge sharing internally between the Cobalt Strike and Outflank R&D teams. We are excited about the innovation opportunities made possible by this teamwork and have decided to align Cobalt Strike and Outflank Security Tooling (OST) closely going forward. Although we are actively collaborating, Cobalt Strike will continue to be the industry standard Command & Control (C2) framework, while OST will continue to offer a red team toolbox for all environments containing custom tradecraft that is OPSEC safe, evasive by design, and simple to use. Our vision is that Cobalt Strike and OST together will provide the best red team offering on the planet. 

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So you think you can block Macros?

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For the purpose of securing Microsoft Office installs we see many of our customers moving to a macro signing strategy. Furthermore, Microsoft is trying to battle macro malware by enforcing Mark-of-the-Web (MotW) control on macro-enabled documents. In this blog we will dive into some of the quirks of Microsoft Office macro security, various commonly used configuration options and their bypasses.

  • In the first part of the blog we will discuss various Microsoft Office security controls on macros and add-ins, including their subtleties, pitfalls and offensive bypasses.
  • In the second part of this blog the concept of LOLdocs is further explained, detailing how vulnerabilities in signed MS Office content might be abused to bypass even strictly configured MS Office installs.

This blog is related to our BruCON talk on LOLdocs: legitimately signed Office documents where control flows can be hijacked for malicious purposes.

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Attacking Visual Studio for Initial Access

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In this blog post we will demonstrate how compiling, reverse engineering or even just viewing source code can lead to compromise of a developer’s workstation. This research is especially relevant in the context of attacks on security researchers using backdoored Visual Studio projects allegedly by North Korean actors, as exposed by Google. We will show that these in-the-wild attacks are only the tip of the iceberg and that backdoors can be hidden via much stealthier vectors in Visual Studio projects.

This post will be a journey into COM, type libraries and the inner workings of Visual Studio. In particular, it serves the following goals:

  • Exploring Visual Studio’s attack surface for initial access attacks from a red teamer’s perspective.
  • Raising awareness on the dangers of working with untrusted code, which we as hackers and security researchers do on a regular basis.

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A phishing document signed by Microsoft – part 2

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This is the second part of our blog series in which we walk you through the steps of finding and weaponising other vulnerabilities in Microsoft signed add-ins. Our previous post described how a Microsoft-signed Analysis Toolpak Excel add-in (.XLAM) was vulnerable to code hijacking by loading an attacker controlled XLL via abuse of the RegisterXLL function.

In this post we will dive deep into a second code injection vulnerability in the Analysis Toolpak in relation to the use of the ExecuteExcel4Macro function in a Microsoft-signed Excel add-in. Furthermore, we will show that the Solver add-in is vulnerable to a similar weaknesses with yet another vector. In particular, we will discuss:

  • Walkthrough of the Analysis Toolpak code injection vulnerability patched by CVE-2021-28449
  • Exploitation gadgets for practical weaponisation of such a vulnerability
  • Weakness in Solver Add-in
  • Our analysis of Microsoft’s patch

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A phishing document signed by Microsoft – part 1

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This blog post is part of series of two posts that describe weaknesses in Microsoft Excel that could be leveraged to create malicious phishing documents signed by Microsoft that load arbitrary code.

These weaknesses have been addressed by Microsoft in the following patch: CVE-2021-28449. This patch means that the methods described in this post are no longer applicable to an up-to-date and securely configured MS Office install. However, we will uncover a largely unexplored attack surface of MS Office for further offensive research and will demonstrate practical tradecraft for exploitation.

In this blog post (part 1), we will discuss the following:

  • The Microsoft Analysis ToolPak Excel and vulnerabilities in XLAM add-ins which are distributed as part of this.
  • Practical offensive MS Office tradecraft which is useful for weaponizing signed add-ins which contain vulnerabilities,

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Our reasoning for Outflank Security Tooling

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TLDR: We open up our internal toolkit commercially to other red teams. This post explains why.

Is blue catching your offensive actions? Are you relying on public or even commercial tools, but are these flagged by AV and EDR? Hesitant on investing deeply in offensive research and development? We’ve been there. But several years ago, we made the switch and started heavily investing in research. Our custom toolset was born.

Today we open up our toolset to other red teams in a new service called Outflank Security Tooling, abbreviated OST. We are super(!) excited about this. We truly think this commercial model is a win-win and will help other red teams and subsequently many organisations worldwide. You can find all the details at the product page. But there is more to be explained about why we do this,

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Catching red teams with honeypots part 1: local recon

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This post is the first part of a series in which we will cover the concept of using honeypots in a Windows environment as an easy and cost-effective way to detect attacker (or red team) activities. Of course this blog post is about catching real attackers, not just red teams. But we picked this catchy title as the content is based on our red teaming experiences.

Upon mentioning honeypots, a lot of people still think about a system in the network hosting a vulnerable or weakly configured service. However, there is so much more you can do, instead of spawning a system. Think broad: honey files, honey registry keys, honey tokens, honey (domain) accounts or groups, etc.

In this post, we will cover:

  • The characteristics of an effective honeypot.
  • Walkthrough on configuring a file- and registry based honeypots using audit logging and SACLs.

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Direct Syscalls in Beacon Object Files

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In this post we will explore the use of direct system calls within Cobalt Strike Beacon Object Files (BOF). In detail, we will:

  • Explain how direct system calls can be used in Cobalt Strike BOF to circumvent typical AV and EDR detections.
  • Release InlineWhispers: a script to make working with direct system calls more easy in BOF code.
  • Provide Proof-of-Concept BOF code which can be used to enable WDigest credential caching and circumvent Credential Guard by patching LSASS process memory.

Source code of the PoC can be found here:

https://github.com/outflanknl/WdToggle

Source code of InlineWhispers can be found here:

https://github.com/outflanknl/InlineWhispers

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