Cyber Security News: Microsoft Office Vulnerabilities Used to Distribute Zyklon Malware in Recent Campaign

Introduction

FireEye researchers recently observed threat actors leveraging
relatively new vulnerabilities in Microsoft Office to spread Zyklon
HTTP malware. Zyklon has been observed in the wild since early 2016
and provides myriad sophisticated capabilities.

Zyklon is a publicly available, full-featured backdoor capable of
keylogging, password harvesting, downloading and executing additional
plugins, conducting distributed denial-of-service (DDoS) attacks, and
self-updating and self-removal. The malware may communicate with its
command and control (C2) server over The Onion Router (Tor) network if
configured to do so. The malware can download several plugins, some of
which include features such as cryptocurrency mining and password
recovery, from browsers and email software. Zyklon also provides a
very efficient mechanism to monitor the spread and impact.

Infection Vector

We have observed this recent wave of Zyklon malware being delivered
primarily through spam emails. The email typically arrives with an
attached ZIP file containing a malicious DOC file (Figure 1 shows a
sample lure).

The following industries have been the primary targets in this campaign:

Telecommunications
Insurance
Financial Services

Figure 1: Sample lure documents

Attack Flow

Spam email arrives in the
victim’s mailbox as a ZIP attachment, which contains a malicious DOC
file.
The document files exploit at least three known
vulnerabilities in Microsoft Office, which we discuss in the
Infection Techniques section. Upon execution in a vulnerable
environment, the PowerShell based payload takes over.
The
PowerShell script is responsible for downloading the final payload
from C2 server to execute it.

A visual representation of the attack flow and execution chain can
be seen in Figure 2.

Figure 2: Zyklon attack flow

Infection Techniques

CVE-2017-8759

This vulnerability was discovered
by FireEye in September 2017, and it is a vulnerability we have
observed being exploited in the wild.

The DOC file contains an embedded OLE Object that, upon execution,
triggers the download of an additional DOC file from the stored URL
(seen in Figure 3).

Figure 3: Embedded URL in OLE object

CVE-2017-11882

Similarly, we have also observed actors leveraging another
recently discovered
vulnerability (CVE-2017-11882) in Microsoft Office. Upon opening the
malicious DOC attachment, an additional download is triggered from a
stored URL within an embedded OLE Object (seen in Figure 4).

Figure 4: Embedded URL in OLE object

Figure 5: HTTP GET request to download
the next level payload

The downloaded file, doc.doc, is XML-based and contains a
PowerShell command (shown in Figure 6) that subsequently downloads the
binary Pause.ps1.

Figure 6: PowerShell command to download
the Pause.ps1 payload

Dynamic Data Exchange (DDE)

Dynamic Data Exchange (DDE) is the interprocess communication
mechanism that is exploited to perform remote code execution. With the
help of a PowerShell script (shown in Figure 7), the next payload
(Pause.ps1) is downloaded.

Figure 7: DDE technique used to download
the Pause.ps1 payload

One of the unique approaches we have observed is the use of dot-less
IP addresses (example: hxxp://258476380).

Figure 8 shows the network communication of the Pause.ps1 download.

Figure 8: Network communication to
download the Pause.ps1 payload

Zyklon Delivery

In all these techniques, the same domain is used to download the
next level payload (Pause.ps1), which is another PowerShell
script that is Base64 encoded (as seen in Figure 8).

The Pause.ps1 script is responsible for resolving the APIs
required for code injection. It also contains the injectable
shellcode. The APIs contain VirtualAlloc(), memset(), and
CreateThread(). Figure 9 shows the decoded Base64 code.

Figure 9: Base64 decoded Pause.ps1

The injected code is responsible for downloading the final payload
from the server (see Figure 10). The final stage payload is a PE
executable compiled with .Net framework.

Figure 10: Network traffic to download
final payload (words.exe)

Once executed, the file performs the following activities:

Drops a copy of itself in
%AppData%\svchost.exe\svchost.exe and drops an XML file, which
contains configuration information for Task Scheduler (as shown in
Figure 11).
Unpacks the code in memory via process
hollowing. The MSIL file contains the packed core payload in its
.Net resource section.
The unpacked code is Zyklon.

Figure 11: XML configuration file to
schedule the task

The Zyklon malware first retrieves the external IP address of the
infected machine using the following:

api.ipify[.]org
ip.anysrc[.]net
myexternalip[.]com
whatsmyip[.]com

The Zyklon executable contains another encrypted file in its .Net
resource section named tor. This file is decrypted and injected
into an instance of InstallUtiil.exe, and functions as a Tor anonymizer.

Command & Control Communication

The C2 communication of Zyklon is proxied through the Tor network.
The malware sends a POST request to the C2 server. The C2 server is
appended by the gate.php, which is stored in file memory. The
parameter passed to this request is getkey=y. In response to this
request, the C2 server responds with a Base64-encoded RSA public key
(seen in Figure 12).

Figure 12: Zyklon public RSA key

After the connection is established with the C2 server, the malware
can communicate with its control server using the commands shown in
Table 1.

Command	Action
sign	Requests system information
settings	Requests settings from C2 server
logs	Uploads harvested passwords
wallet	Uploads harvested cryptocurrency wallet data
proxy	Indicates SOCKS proxy port opened
miner	Cryptocurrency miner commands
error	Reports errors to C2 server
ddos	DDoS attack commands

Table 1: Zyklon accepted commands

The following figures show the initial request and subsequent server
response for the “settings” (Figure 13), “sign” (Figure 14), and
“ddos” (Figure 15) commands.

Figure 13: Zyklon issuing “settings”
command and subsequent server response

Figure 14: Zyklon issuing “sign” command
and subsequent server response

Figure 15: Zyklon issuing “ddos” command
and subsequent server response

Plugin Manager

Zyklon downloads number of plugins from its C2 server. The plugin
URL is stored in file in following format:

/plugin/index.php?plugin=<Plugin_Name>

The following plugins are found in the memory of the Zyklon malware:

/plugin/index.php?plugin=cuda
/plugin/index.php?plugin=minerd
/plugin/index.php?plugin=sgminer
/plugin/index.php?plugin=socks
/plugin/index.php?plugin=tor
/plugin/index.php?plugin=games
/plugin/index.php?plugin=software
/plugin/index.php?plugin=ftp
/plugin/index.php?plugin=email
/plugin/index.php?plugin=browser

The downloaded plugins are injected into: Windows\Microsoft.NET\Framework\v4.0.30319\RegAsm.exe.

Additional Features

The Zyklon malware offers the following additional capabilities (via plugins):

Browser Password Recovery

Zyklon HTTP can recover passwords from popular web browsers, including:

Google Chrome
Mozilla Firefox
Internet Explorer
Opera
Browser
Chrome Canary/SXS
CoolNovo Browser
Apple Safari
Flock Browser
SeaMonkey
Browser
SRWare Iron Browser
Comodo Dragon
Browser

FTP Password Recovery

Zyklon currently supports FTP password recovery from the following
FTP applications:

FileZilla
SmartFTP
FlashFXP
FTPCommander
Dreamweaver
WS_FTP

Gaming Software Key Recovery

Zyklon can recover PC Gaming software keys from the following games:

Battlefield
Call
of Duty
FIFA
NFS
Age of Empires
Quake
The Sims
Half-Life
IGI
Star Wars

Email Password Recovery

Zyklon may also collect email passwords from following applications:

Microsoft Outlook
Express
Microsoft Outlook 2002/XP/2003/2007/2010/2013
Mozilla Thunderbird
Windows Live Mail 2012
IncrediMail, Foxmail v6.x - v7.x
Windows Live
Messenger
MSN Messenger
Google Talk
GMail
Notifier
PaltalkScene IM
Pidgin (Formerly Gaim)
Messenger
Miranda Messenger
Windows Credential
Manager

License Key Recovery

The malware automatically detects and decrypts the license/serial
keys of more than 200 popular pieces of software, including Office,
SQL Server, Adobe, and Nero.

Socks5 Proxy

Zyklon features the ability to establish a reverse Socks5 proxy
server on infected host machines.

Hijack Clipboard Bitcoin Address

Zyklon has the ability to hijack the clipboard, and replaces the
user’s copied bitcoin address with an address served up by the actor’s
control server.

Zyklon Pricing

Researchers identified different versions of Zyklon HTTP being
advertised in a popular underground marketplace for the following prices:

Normal build: $75
(USD)
Tor-enabled build: $125 (USD)
Rebuild/Updates:
$15 (USD)
Payment Method: Bitcoin (BTC)

Conclusion

Threat actors incorporating recently discovered vulnerabilities in
popular software – Microsoft Office, in this case – only increases the
potential for successful infections. These types of threats show why
it is very important to ensure that all software is fully updated.
Additionally, all industries should be on alert, as it is highly
likely that the threat actors will eventually move outside the scope
of their current targeting.

At this time of writing, FireEye Multi Vector Execution (MVX)
engine is able to recognize and block this threat. Table 2 lists
the current detection and blocking capabilities by product.

Detection Name	Product	Action
POWERSHELL DOWNLOADER D (METHODOLOGY)	HX	Detect
SUSPICIOUS POWERSHELL USAGE (METHODOLOGY)	HX	Detect
POWERSHELL DOWNLOADER (METHODOLOGY)	HX	Detect
SUSPICIOUS EQNEDT USAGE (METHODOLOGY)	HX	Detect
TOR (TUNNELER)	HX	Detect
SUSPICIOUS SVCHOST.EXE (METHODOLOGY)	HX	Detect
Malware.Binary.rtf	EX/ETP/NX	Block
Malware.Binary	EX/ETP/NX	Block
FE_Exploit_RTF_CVE_2017_8759	EX/ETP/NX	Block
FE_Exploit_RTF_CVE201711882_1	EX/ETP/NX	Block

Table 2: Current detection capabilities by
FireEye products

Indicators of Compromise

The contained analysis is based on the representative sample lures
shown in Table 3.

MD5	Name
76011037410d031aa41e5d381909f9ce	accounts.doc
4bae7fb819761a7ac8326baf8d8eb6ab	Courier.doc
eb5fa454ab42c8aec443ba8b8c97339b	doc.doc
886a4da306e019aa0ad3a03524b02a1c	Pause.ps1
04077ecbdc412d6d87fc21e4b3a4d088	words.exe

Table 3: Sample Zyklon lures

The post Microsoft Office Vulnerabilities Used to Distribute Zyklon Malware in
Recent Campaign appeared first on Security Boulevard.

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Cyber Security News

Wednesday, January 17, 2018

Microsoft Office Vulnerabilities Used to Distribute Zyklon Malware in Recent Campaign