054. Detecting CypherIT Crypter Behaviors

Hello everyone! I think it's not a secret that many adversaries leverage crypters to evade defenses. But some crypters not only encrypt and obfuscate maicious code, but also have intersting behaviors we can use for detection engeneering!


Let's look at CypherIT - a very popular crypter, which used to be sold on underground resources, and used by lots of various threat actors worldwide (for example, Sticky Werewolf).

The first behavior example we'll look at is abusing findstr for AV discovery:

findstr /I "opssvc wrsa"

findstr "bdservicehost AvastUI AVGUI nsWscSvc ekrn SophosHealth"

To detect it, search for findstr executions with AV/EDR names in command line (you can expand this list, of course):

event_type: "processcreate" 

AND 

proc_file_name: "findstr.exe" 

AND 

cmdline: (*wrsa* OR *opssvc* OR *avastui* OR *avgui* OR *nswscsvc* OR *sophoshealth* OR *bdservicehost* OR *ekrn*)

Next noteworthy behavior - dropping and executing renamed AutoIt interpreter to run a malicious script, for example:

Philip.com N

Renamed AutoIt executions are not very common for corporate environments, so we can build detection logic based on this feature:

event_type: "processcreate" 

AND

proc_file_originalfilename: "AutoIt3.exe" 

AND NOT

proc_file_name: "autoit3.exe"

As always, there are more! Try to find it, here's a sample for you. 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