Security researchers warn that hackers may start using Microsoft Visual Studio Tools for Office (VSTO) more often as method to achieve persistence and execute code on a target machine via malicious Office add-ins.
The technique is an alternative to sneaking into documents VBA macros that fetch malware from an external source.
Since Microsoft announced it would
block the execution of VBA and XL4 macros in Office by default, threat actors moved to archives (.ZIP, .ISO) and .LNK shortcut files to distribute their malware.
However, using VSTO introduce an attack vector that allows building .NET-based malware and embedding it into the Office add-in.
Security researchers at
Deep Instinct discovered multiple such attacks recently and believe that skillful hackers are increasingly adopting the method.
Although
VSTO-based attacks are not new, they are a rare occurrence and have not been too much of a
concern for the infosec community.
