.SettingContent-ms files remind us that it is features, not bugs we should be most concerned about

Posted by   Martijn Grooten on   Jul 3, 2018

One of the most significant developments in the threat landscape in recent years has been the return of malicious Office macros, their resurgence having started four years ago.

Unlike their predecessors from the 1990s, these macros can't run automatically, but require the user to explicitly enable macros. This obviously mitigates the damage quite a bit, but not enough to stop this being an attractive infection method for both opportunistic and targeted malware attacks.

Since then, malware authors have been looking for other features that can be abused in a similar way. Last year, researchers at Sensepost discovered that the Dynamic Data Exchange (DDE) protocol could be used to deliver malware. Now, security researcher Matt Nelson has found another such method: the .SettingContent-ms filetype.

Introduced in Windows 10, these are XML files that are essentially shortcuts to the Windows Control Panel. However, Nelson found that they can also be used to run other commands, including PowerShell code. And thus they can be used to run or download malware.

Because .SettingContent-ms files are not listed as known bad file types in Office, they can also be embedded into Office documents – when opened, all the user has to do is confirm they want to open the file and the device will be infected with malware. (When downloaded directly from the Internet, the files are run without any warning, but Nelson rightly believes that this is a less likely infection vector.)

settingcontent-ms.png

The warning shown to the user when opening a .SettingContent-ms file embedded in an Office document. Source: Matt Nelson.

As per its recently published policy for patching and servicing, Microsoft has decided not to fix this issue, though of course this may change in the future; Microsoft did eventually disable DDE after it became a popular way for malware to spread.

As operating systems and software is becoming more secure, both malware authors and white hat researchers will increasingly be looking for exploitable features rather than bugs. Though some features can be disabled, if a user has the system privileges to perform an action, they can probably be socially engineered to do so.

One way to mitigate this risk is to harden systems by limiting the number of things a user can do. I have previously recommended the iPhone for high-risk users for this very reason.

The risk can also be mitigated by using security software. Though many security experts are rightly sceptical of the bold promises made in product marketing, there is no question that security software does a much better job than most users at deciding what programs and scripts should be allowed to run.

So far, there have been no reports of this technique being used in the wild. Several security vendors already claim that their product would block this kind of infection; if you work for a vendor, it might be a good idea to check whether yours does too.

twitter.png
fb.png
linkedin.png
hackernews.png
reddit.png

 

Latest posts:

Nominations opened for sixth Péter Szőr Award

Virus Bulletin is seeking nominations for the sixth annual Péter Szőr Award.

Haroon Meer and Adrian Sanabria to deliver VB2019 closing keynote

New additions to the VB2019 conference programme include a closing keynote address from Thinkst duo Haroon Meer and Adrian Sanabria and a talk on attacks against payment systems.

Free VB2019 tickets for students

Virus Bulletin is excited to announce that, thanks to generous sponsorship from Google Android, we are able to offer 20 free tickets to students who want to attend VB2019.

VB2018 paper: Lazarus Group: a mahjong game played with different sets of tiles

The Lazarus Group, generally linked to the North Korean government, is one of the most notorious threat groups seen in recent years. At VB2018 ESET researchers Peter Kálnai and Michal Poslušný presented a paper looking at the group's various…

Book your VB2019 ticket now for a chance to win a ticket for BSides London

Virus Bulletin is proud to sponsor this year's BSides London conference, which will take place next week, and we have a number of tickets to give away.

We have placed cookies on your device in order to improve the functionality of this site, as outlined in our cookies policy. However, you may delete and block all cookies from this site and your use of the site will be unaffected. By continuing to browse this site, you are agreeing to Virus Bulletin's use of data as outlined in our privacy policy.