Stephan Berger Profile picture
Apr 6, 2022 8 tweets 4 min read Read on X
Real-World #PingCastle Finding #8: Non-admin users can add computers to a domain. A customer called us because he discovered two new computer objects. Such new computer objects can be a sign of more targeted attacks against the #ActiveDirectory.
1/8

#CyberSecurity #dfir
The computer names are relatively unique, and one quickly finds a GitHub repository with corresponding exploit code.

The code tries to exploit the two vulnerabilities CVE-2021-42278 and CVE-2021-42287 (from an authenticated user directly to DA).
2/8

github.com/WazeHell/sam-t…
Inside the exploit code, a new computer name is generated following the pattern SAMTHEADMIN-(random number from 1 to 100), precisely the naming scheme we see in the client's AD.
3/8
A few lines further down, the value of MachineAccountQuota is read from the domain policy.
4/8
If this value < 0, the exploit aborts. Which brings us to the PingCastle finding.
5/8

@mysmartlogon
Ping Castle also checks the value of MachineAccountQuota, and outputs a corresponding finding if the value is < 0.

"This default configuration represents a security issue as regular users shouldn't be able to create such accounts, and administrators should handle this task."
6/8
The recommendation is to adjust the value of MachineAccountQuota and only allow authorized users to add computers to the domain.
7/8
The customer found the computer objects by reviewing the AD objects - an excellent hint that such unusual objects may be part of an ongoing attack, and to periodically review the objects inside the AD.
8/8

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More from @malmoeb

Jun 16, 2023
1/ We recently had an interesting #Azure case where the TA, instead of creating a new Inbox Rule, added email addresses of interest to the list of blocked senders and domains.

The incoming emails will get flagged as spam and moved to the Junk email folder. 📂

🧵
2/ Here is a screenshot from Outlook web access

(the view might differ, as, for example, here on the screenshot from the theitbros [1]) Image
3/ And here from an Outlook client: Image
Read 11 tweets
Apr 18, 2023
1/ Customer receives an email from a network monitoring device that a host is supposedly infected with a #CoinMiner. The Task Manager on the said system shows the following screenshot 🤕.

A story of an unpatched system, incorrect scoping, and 🍀. 🧵

#CyberSecurity Image
2/ The affected (and remotely accessible) server have had Confluence installed.

One of my first questions I asked the customer was if the system was up to date (Spoiler: it wasn't).

Confluence 6.0.4 was installed at the time of the incident.
3/ Confluence 6.0.4 was released in January 2017 🤯 Image
Read 14 tweets
Apr 17, 2023
1/ I used #AutoRuns v14.09 (GUI) in my lab setup but noticed that it failed to find (or display) the malware in the Startup folder, although the file is there (screenshot below).

I checked back and forth, searched manually for the file, and restarted the OS and AutoRuns.

🧵 Image
2/ With #Velociraptor, I ran the hunt Sysinternals.Autoruns, and with the CLI version of AutoRuns, the malware is found in the Startup folder. Image
3/ The same for the #Velociraptor hunt Sys.StartupItems. Image
Read 4 tweets
Mar 21, 2023
1/ The content below is from a file named install.bat and stems from a recent investigation where a TA launched this batch file. 👀

What's going on?

Well, VboxUpdate.exe is, in fact, tor.exe, and a new service is created, launching tor with a config file.

🧵 #CyberSecurity Image
2/ Below is an excerpt from the content of config.txt; the configuration file passed as an argument to the tor service.

If you think this looks a lot like RDP Tunneling, you are absolutely right. 🥇 Image
3/ Head over to the allthingsdfir blog to read a more profound write-up about the techniques used here and how they work together.

allthingsdfir.com/rdp-over-tor/
Read 5 tweets
Mar 20, 2023
1/ Real-World #PingCastle Finding #13: Allow log on locally

➡️ Domain Users are eligible to log into DC's 🤯🙈

"When you grant an account the Allow logon locally right, you are allowing that account to log on locally to all domain controllers in the domain." [1]

#CyberSecurity Image
2/ Why is this a bad idea?

"If you do not restrict this user right to legitimate users who must log on to the console of the computer, unauthorized users could download and run malicious software to elevate their privileges." [1]
3/ I encountered this finding several times in our AD assessments, so you better check your settings in your domain right now (better safe than sorry 🔒).

Good luck 🍀
Read 4 tweets
Mar 18, 2023
1/ Do you monitor newly created services within your environment, and would you notice when a (vulnerable) driver is loaded?

The screenshot below (#Velociraptor 🤩) is from a recent #XMRig CoinMiner investigation ⤵️

🧵 #CyberSecurity
2/ We talked about vulnerable drivers before:

Read 4 tweets

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