Posté par: igor51 le février 10, 2018, 01:00:42
Threat Group, Using CVE-2017-11882 Exploit
Less than a week after Microsoft issued a patch for
on Nov. 14, 2017, FireEye observed an attacker using an exploit for
the Microsoft Office vulnerability to target a government organization
in the Middle East. We assess this activity was carried out by a
suspected Iranian cyber espionage threat group, whom we refer to as
APT34, using a custom PowerShell backdoor to achieve its objectives.
We believe APT34 is involved in a long-term cyber espionage
operation largely focused on reconnaissance efforts to benefit Iranian
nation-state interests and has been operational since at least 2014.
This threat group has conducted broad targeting across a variety of
industries, including financial, government, energy, chemical, and
telecommunications, and has largely focused its operations within the
Middle East. We assess that APT34 works on behalf of the Iranian
government based on infrastructure details that contain references to
Iran, use of Iranian infrastructure, and targeting that aligns with
nation-state interests.
APT34 uses a mix of public and non-public tools, often conducting
spear phishing operations using compromised accounts, sometimes
coupled with social engineering tactics. In May 2016, we published a
blog detailing a
phishing campaign targeting banks in the Middle East region that
used macro-enabled attachments to distribute POWBAT malware. We now
attribute that campaign to APT34. In July 2017, we observed APT34
targeting a Middle East organization using a PowerShell-based backdoor
that we call POWRUNER and a downloader with domain generation
algorithm functionality that we call BONDUPDATER, based on strings
within the malware. The backdoor was delivered via a malicious .rtf
file that exploited CVE-2017-0199.
In this latest campaign, APT34 leveraged the recent Microsoft Office
vulnerability CVE-2017-11882 to deploy POWRUNER and BONDUPDATER.
The full report on APT34 is available to our
customer community. APT34 loosely aligns with
reporting related to the group "OilRig". As individual
organizations may track adversaries using varied data sets, it is
possible that our classifications of activity may not wholly align.
CVE-2017-11882: Microsoft Office Stack Memory Corruption Vulnerability
CVE-2017-11882 affects several versions of Microsoft Office and,
when exploited, allows a remote user to run arbitrary code in the
context of the current user as a result of improperly handling objects
in memory. The vulnerability was patched by Microsoft on Nov. 14,
2017. A full proof of concept (POC) was publicly released a week later
by the reporter of the vulnerability.
The vulnerability exists in the old Equation Editor (EQNEDT32.EXE),
a component of Microsoft Office that is used to insert and evaluate
mathematical formulas. The Equation Editor is embedded in Office
documents using object linking and embedding (OLE) technology. It is
created as a separate process instead of child process of Office
applications. If a crafted formula is passed to the Equation Editor,
it does not check the data length properly while copying the data,
which results in stack memory corruption. As the EQNEDT32.exe is
compiled using an older compiler and does not support address space
layout randomization (ASLR), a technique that guards against the
exploitation of memory corruption vulnerabilities, the attacker can
easily alter the flow of program execution.
Analysis
APT34 sent a malicious .rtf file (MD5:
a0e6933f4e0497269620f44a083b2ed4) as an attachment in a malicious
spear phishing email sent to the victim organization. The malicious
file exploits CVE-2017-11882, which corrupts the memory on the stack
and then proceeds to push the malicious data to the stack. The malware
then overwrites the function address with the address of an existing
instruction from EQNEDT32.EXE. The overwritten instruction (displayed
in Figure 1) is used to call the “WinExec” function from kernel32.dll,
as depicted in the instruction at 00430c12, which calls the “WinExec” function.
Figure 1: Disassembly of overwritten
function address
After exploitation, the ‘WinExec’ function is successfully called to
create a child process, “mshta.exe”, in the context of current logged
on user. The process “mshta.exe” downloads a malicious script from
hxxp://mumbai-m[.]site/b.txt and executes it, as seen in Figure 2.
Figure 2: Attacker data copied to corrupt
stack buffer
Execution Workflow
The malicious script goes through a series of steps to successfully
execute and ultimately establish a connection to the command and
control (C2) server. The full sequence of events starting with the
exploit document is illustrated in Figure 3.
Figure 3: CVE-2017-11882 and POWRUNER
attack sequence
- The malicious .rtf file
exploits CVE-2017-11882. - The malware overwrites the
function address with an existing instruction from
EQNEDT32.EXE. - The malware creates a child process,
“mshta.exe,” which downloads a file from:
hxxp://mumbai-m[.]site/b.txt. - b.txt contains a PowerShell
command to download a dropper from: hxxp://dns-update[.]club/v.txt.
The PowerShell command also renames the downloaded file from v.txt
to v.vbs and executes the script. - The v.vbs script drops
four components (hUpdateCheckers.base, dUpdateCheckers.base,
cUpdateCheckers.bat, and GoogleUpdateschecker.vbs) to the directory:
C:\ProgramData\Windows\Microsoft\java\ - v.vbs uses
CertUtil.exe, a legitimate Microsoft command-line program installed
as part of Certificate Services, to decode the base64-encoded files
hUpdateCheckers.base and dUpdateCheckers.base, and drop
hUpdateCheckers.ps1 and dUpdateCheckers.ps1 to the staging
directory. - cUpdateCheckers.bat is launched and creates a
scheduled task for GoogleUpdateschecker.vbs persistence. - GoogleUpdateschecker.vbs is executed after sleeping for five
seconds. - cUpdateCheckers.bat and *.base are deleted from the
staging directory.
Figure 4 contains an excerpt of the v.vbs script pertaining to the
Execution Workflow section.
Figure 4: Execution Workflow Section of v.vbs
After successful execution of the steps mentioned in the Execution
Workflow section, the Task Scheduler will launch
GoogleUpdateschecker.vbs every minute, which in turn executes the
dUpdateCheckers.ps1 and hUpdateCheckers.ps1 scripts. These PowerShell
scripts are final stage payloads – they include a downloader with
domain generation algorithm (DGA) functionality and the backdoor
component, which connect to the C2 server to receive commands and
perform additional malicious activities.
hUpdateCheckers.ps1 (POWRUNER)
The backdoor component, POWRUNER, is a PowerShell script that sends
and receives commands to and from the C2 server. POWRUNER is executed
every minute by the Task Scheduler. Figure 5 contains an excerpt of
the POWRUNER backdoor.
Figure 5: POWRUNER PowerShell script hUpdateCheckers.ps1
POWRUNER begins by sending a random GET request to the C2 server and
waits for a response. The server will respond with either “not_now” or
a random 11-digit number. If the response is a random number, POWRUNER
will send another random GET request to the server and store the
response in a string. POWRUNER will then check the last digit of the
stored random number response, interpret the value as a command, and
perform an action based on that command. The command values and the
associated actions are described in Table 1.
Command | valign="top"> | valign="top"> |
0 | valign="top"> | Execute batch |
1 | valign="top"> | Check for file path and |
2 | valign="top"> | Check for file path and |
Table 1: POWRUNER commands
After successfully executing the command, POWRUNER sends the results
back to the C2 server and stops execution.
The C2 server can also send a PowerShell command to capture and
store a screenshot of a victim’s system. POWRUNER will send the
captured screenshot image file to the C2 server if the “fileupload”
command is issued. Figure 6 shows the PowerShell “Get-Screenshot”
function sent by the C2 server.
Figure 6: Powershell Screenshot Functionality
dUpdateCheckers.ps1 (BONDUPDATER)
One of the recent advancements by APT34 is the use of DGA to
generate subdomains. The BONDUPDATER script, which was named based on
the hard-coded string “B007”, uses a custom DGA algorithm to generate
subdomains for communication with the C2 server.
DGA Implementation
Figure 7 provides a breakdown of how an example domain
(456341921300006B0C8B2CE9C9B007.mumbai-m[.]site) is generated using
BONDUPDATER’s custom DGA.
Figure 7: Breakdown of subdomain created
by BONDUPDATER
- This is a randomly
generated number created using the following expression: $rnd =
-join (Get-Random -InputObject (10..99) -Count (%{ Get-Random
-InputObject (1..6)})); - This value is either 0 or 1. It is
initially set to 0. If the first resolved domain IP address starts
with 24.125.X.X, then it is set to 1. - Initially set to 000,
then incremented by 3 after every DNS request - First 12
characters of system UUID. - “B007” hardcoded string.
- Hardcoded domain “mumbai-m[.]site”
BONDUPDATER will attempt to resolve the resulting DGA domain and
will take the following actions based on the IP address resolution:
- Create a temporary file
in %temp% location- The file created will have the last two
octets of the resolved IP addresses as its filename.
- The file created will have the last two
- BONDUPDATER will evaluate the last character of the file
name and perform the corresponding action found in Table 2.
Character | |
0 | valign="top"> |
1 | valign="top"> |
2 | valign="top"> |
Table 2: BONDUPDATER Actions
Figure 8 is a screenshot of BONDUPDATER’s DGA implementation.
Figure 8: Domain Generation Algorithm
Some examples of the generated subdomains observed at time of
execution include:
143610035BAF04425847B007.mumbai-m[.]site
835710065BAF04425847B007.mumbai-m[.]site
376110095BAF04425847B007.mumbai-m[.]site
Network Communication
Figure 9 shows example network communications between a POWRUNER
backdoor client and server.
Figure 9: Example Network Communication
In the example, the POWRUNER client sends a random GET request to
the C2 server and the C2 server sends the random number (99999999990)
as a response. As the response is a random number that ends with ‘0’,
POWRUNER sends another random GET request to receive an additional
command string. The C2 server sends back Base64 encoded response.
If the server had sent the string “not_now” as response, as shown in
Figure 10, POWRUNER would have ceased any further requests and
terminated its execution.
Figure 10: Example "not now"
server response
Batch Commands
POWRUNER may also receive batch commands from the C2 server to
collect host information from the system. This may include information
about the currently logged in user, the hostname, network
configuration data, active connections, process information, local and
domain administrator accounts, an enumeration of user directories, and
other data. An example batch command is provided in Figure 11.
Figure 11: Batch commands sent by
POWRUNER C2 server
Additional Use of POWRUNER / BONDUPDATER
APT34 has used POWRUNER and BONDUPDATER to target Middle East
organizations as early as July 2017. In July 2017, a FireEye Web MPS
appliance detected and blocked a request to retrieve and install an
APT34 POWRUNER / BONDUPDATER downloader file. During the same month,
FireEye observed APT34 target a separate Middle East organization
using a malicious .rtf file (MD5: 63D66D99E46FB93676A4F475A65566D8)
that exploited CVE-2017-0199. This file issued a GET request to
download a malicious file from:
hxxp://94.23.172.164/dupdatechecker.doc.
As shown in Figure 12, the script within the dupatechecker.doc file
attempts to download another file named dupatechecker.exe from the
same server. The file also contains a comment by the malware author
that appears to be an apparent taunt to security researchers.
Figure 12: Contents of dupdatechecker.doc script
The dupatechecker.exe file (MD5: C9F16F0BE8C77F0170B9B6CE876ED7FB)
drops both BONDUPDATER and POWRUNER. These files connect to
proxychecker[.]pro for C2.
Outlook and Implications
Recent activity by APT34 demonstrates that they are capable group
with potential access to their own development resources. During the
past few months, APT34 has been able to quickly incorporate exploits
for at least two publicly vulnerabilities (CVE-2017-0199 and
CVE-2017-11882) to target organizations in the Middle East.
We assess that APT34’s efforts to continuously update their malware,
including the incorporation of DGA for C2, demonstrate the group’s
commitment to pursing strategies to deter detection. We expect APT34
will continue to evolve their malware and tactics as they continue to
pursue access to entities in the Middle East region.
IOCs
| |
CVE-2017-11882 exploit | valign="top"> |
b.txt | valign="top"> |
v.txt/v.vbs | |
dUpdateCheckers.base | |
hUpdateCheckers.base | |
cUpdateCheckers.bat | |
dUpdateCheckers.ps1 | |
hUpdateCheckers.ps1 | |
GoogleUpdateschecker.vbs | valign="top"> |
hxxp://mumbai-m[.]site | POWRUNER C2 |
hxxp://dns-update[.]club | Malware Staging Server |
CVE-2017-0199 exploit document | valign="top"> |
94.23.172.164:80 | |
dupdatechecker.doc | |
dupdatechecker.exe | |
proxycheker[.]pro | |
46.105.221.247 | |
148.251.55.110 | |
185.15.247.147 | |
145.239.33.100 | |
82.102.14.219 | |
v7-hpserver.online.hta | valign="top"> |
dUpdateCheckers.base | |
hUpdateCheckers.base | |
cUpdateCheckers.bat | |
dUpdateCheckers.ps1 | |
hUpdateCheckers.ps1 | |
googleupdateschecker.vbs | valign="top"> |
hpserver[.]online | |
v7-anyportals.hta | |
dUpdateCheckers.base | |
hUpdateCheckers.base | |
dUpdateCheckers.ps1 | |
hUpdateCheckers.ps1 | |
anyportals[.]com |
Source: New Targeted Attack in the Middle East by APT34, a Suspected Iranian
Threat Group, Using CVE-2017-11882 Exploit (http://)