Mark-of-the-Web
Last updated
Last updated
VBA macros are a common way for malicious actors to gain access to deploy malware and ransomware. Therefore, to help improve security in Office, we’re changing the default behavior of Office applications to block macros in files from the internet.
With this change, when users open a file that came from the internet, such as an email attachment, and that file contains macros, the following message will be displayed:
Strategies to get rid of MOTWFrom a red teamer’s perspective, there are two strategies we can employ to evade MOTW. All of the techniques that we have witnessed in the wild can be categorized under the following two strategies:
Abusing software that does not set MOTW – delivering your payload in a file format which is handled by software that does not set or propagate Zone Identifier information.
Abusing container formats – delivering your payload in a container format which does not support NTFS’ alternate data stream feature.
Another famous example of software that does not set a Zone.Identifier ADS is 7Zip. This archiving client only sets a MOTW flag when a file is double-clicked from the GUI, which means the file is extracted to the temp directory and opened from there. However, upon manual extraction of files to other locations (i.e. clicking the extract button instead of double-clicking), 7Zip does not propagate a Zone.Identifier ADS for extracted files. Note that this works regardless of the archiving file format: any extension handled by 7zip (7z, zip, rar, etc) will demonstrate this behavior.
