171. Detecting BlueNoroff's Indicator Removal Techniques

Hello everyone!

Huntress has shared the results of analysis of a recent BlueNoroff attack involving a macOS device, a fake Zoom extension and even deepfakes! So, let's look at some detection opportunities!

Let's look at indicator removal techniques. The adversary abused environment variable HISTFILE:

unset HISTFILE

We can definitely use it for detection:

event_type: "processcreatemac"

AND

cmdline: "unset histfile"

Next behavior - removing shell history:

history -p > /dev/null

This can also be used for detection:

event_type: "processcreatemac"

AND

proc_file_name: "history"

AND

cmdline: "dev//null"

Finally, the threat actors remove shell history files:

rm -rf ~/.zsh_history

rm -rf ~/.bash_history

rm -rf ~/.zsh_sessions

And yes, this is another detection opportunity:

event_type: "processcreatemac"

AND

proc_file_name: "rm"

AND

cmdline: ("zsh_history" OR "bash_history" OR "zsh_sessions")

See you tomorrow!

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