.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:

VB2018 paper and video: Android app deobfuscation using static-dynamic cooperation

Static analysis and dynamic analysis each have their shortcomings as methods for analysing potentially malicious files. Today, we publish a VB2018 paper by Check Point researchers Yoni Moses and Yaniv Mordekhay, in which they describe a method that…

VB2019 call for papers closes this weekend

The call for papers for VB2019 closes on 17 March, and while we've already received many great submissions, we still want more!

Registration open for VB2019 ─ book your ticket now!

Registration for VB2019, the 29th Virus Bulletin International Conference, is now open, with an early bird rate available until 1 July.

The VB2019 call for papers is about ... papers

When we are calling for papers for the Virus Bulletin conference as we are doing now, we really mean a written paper. But don't worry if you've never written a paper - we can help!

VB2018 video: Adware is just malware with a legal department - how we reverse engineered OSX/Pirrit, received legal threats, and survived

Amit Serper first analysed the OSX/Pirrit adware in 2016, highlighting some of its malware-like techniques, and soon afterwards started receiving legal threats from the company behind it. At VB2018 Amit gave a presentation in which he discussed both…

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.