Hackers always lookout for legitimate programs or application to evade detection and to execute code with minimal user interaction.
Matt Nelson from SpecterOps recently published research on how attackers could abuse “.SettingContent-ms” file formats to run arbitrary commands on the latest version of windows.
[New Post] The Tale of SettingContent-ms Files: https://t.co/jS2ojrmm2l
Includes: One click hyperlink execution, Office 2016 OLE block list evasion and ASR child proc rule evasion.
— Matt Nelson (@enigma0x3) June 11, 2018
Bad Actors Adopted – FlawedAmmyy RAT
The SettingContent-ms file introduced in Windows 10, it is an XML document used to create shortcuts to various Windows 10 setting pages. Proofpoint researchers observed TA505 hacking group using this new technique to spread FlawedAmmyy RAT.
Threat actors embed the SettingContent-ms file inside the Microsoft Word and PDF documents. “The interesting aspect of this file is the <DeepLink> element in the schema. This element takes any binary with parameters and executes it.”
So if the users open a PDF file attachment with an embedded SettingContent-ms file, then windows would automatically run SettingContent-ms file and the PowerShell command contained within the “DeepLink” which leads to download and execute the FlawedAmmyy RAT.
The FlawedAmmy RAT functions
Remote Desktop control
File system manager
Researchers observed the campaign first on June 18 and later on July 16 a large campaign with hundreds of thousands of messages attempting to deliver PDF attachments with an embedded SettingContent-ms file.
“TA505 acting as an early adopter, adapting the abuse of SettingContent-ms files to a PDF-based attack delivered at significant scale. We will continue to monitor ways in which threat actors use this approach in the weeks to come.” Proofpoint researchers said.
To best way to defend this attack is to block.SettingContent-ms, with the Microsoft recent update on the list of dangerous files to block within Office 365 documents, “.SettingContent-ms” file has been added.