387. Adversaries Found a Creative Way to Abuse MSBuild

Hello everyone!

Today we’ll take a look at a creative implementation of a very popular technique - Spearphishing Link (T1566.002).

According to this research, in February 2026 the TA416 cluster was distributing phishing emails containing links that led to Google Drive or compromised SharePoint instances. These links hosted archives that contained a renamed MSBuild executable (for example, Invitation_Letter_No.02_2026) along with a CSPROJ project file, which is what actually got executed after launch - MSBuild by default looks for the corresponding project file in the current directory.

A successful execution resulted in the download of three files, which were later used to implement the DLL sideloading technique.

Despite the attackers’ creative approach, detecting this kind of MSBuild abuse is fairly straightforward. For example:

event_type: "processcreatewin"

AND

proc_file_originalfilename: "msbuild.exe"

AND NOT

proc_file_path: "msbuild.exe"

See you soon!

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