058. Hunting for Ghostwriter

Hello everyone! Let's talk about threat hunting this time. What's the difference between threat detection and threat hunting? When you're writing detections, there must be very low false positive rate, when you're hunting, the query output should include lots of noise - it allows you to uncover threats, which we not detected.

One of my favourites for threat hunting missions - rundll32.exe abuse. It's EXTREMELY common. Let's look at a recent Ghostwriter campaign described in this report by SentinelLABS.

So, the adversary actively abused rundll32exe to execute malicious DLLs. Here are some procedure examples:

rundll32.exe "C:\Users\<USER>\AppData\Roaming\Microsoft\bruhdll32.dll",FckUDud

rundll32.exe "C:\Users\<USER>\AppData\Roaming\Microsoft\bruhdll32.dll",HelloWorld

rundll32.exe "C:\Users\<USER>\AppData\Roaming\Microsoft\bruhdll32.dll",FCKU

rundll32 "C:\Users\<USER>\AppData\Roaming\Microsoft\SystemCertificates\CertificateCenter.dll",#1

I think, you also noted very interesting function names - a very good indication of suspicious activity. Also, we can see that each path includes "Roaming\Microsoft", so we can use it for our hunting query:

event_type: "processcreate"

AND

proc_file_name: "rundll32.exe"

AND

cmdline: "Roaming\\Microsoft"

Always note paths used by threat actors use to store malicious DLLs - it's great fuel for your rundll32.exe abuse hunting missions!

See you tomorrow!

Comments

Post a Comment

Popular posts from this blog

033. Free Google Threat Intelligence Course

Image
Hello everyone! Everybody loves free courses, right? Have you missed a free course on Google Threat Intelligence ? If the answer is "Yes", it's your chance to check it!  I like this course as it not only overviews the capabilities of Google Threat Intelligence as a product, but also covers various threat intelligence use cases, for example, how to empower incident response and forensic investigations or how to use it for adversary hunting and tracking. I've already got my completion badge: What about you? See you tomorrow!
Read more

001. The Zeltser Challenge

Image
Hello everyone! Happy New Year! New year - new challenges! So, a few weeks ago David Cowen reminded me about the Zeltser challenge. What's the point? You must blog every day for a year to push yourself to research and write. Sound cool, right? Dave suggested to start the challenge with him on 1/1/25, and that's why you are reading this post! So, what am I going to share here? I'm a big fan of intelligence-led approach to cyber defense, so every day we'll look at this or that technique (or sub-technique) leveraged by real adversaries, so we can learn more about our enemies.  We'll look both at public reporting and private findings by BI.ZONE Threat Intelligence team. Stay tuned, and see you tomorrow!
Read more

012. They Want to Know Everything About Your System!

Image
Hello everyone! Today we'll look at reconnaissance techniques leveraged by Secret Blizzard (also known as Turla) as seen in the report by Microsoft Threat Intelligence.  In this campaign Secret Blizzard used the Amadey bot to download its own backdoors to specifically selected target devices associated with the Ukrainian military. So, one of the batch scripts leveraged by adversary invoked lots of reconnaissance commands. Let's look at each of them: ver - to collect information about OS version; systeminfo - to collect compromised system information; ipconfig /all - to collect the full TCP/IP configuration for all adapters; ipconfig /displaydns - to collect the contents of the DNS client resolver cache; route print - to collect the entries in the local IP routing table; arp -a - to collect information on current arp cache tables for all interfaces; netstat -a -n - to collect information on active network connections; net share - to collect information on ...
Read more