We observed new targeted attacks targeting various personnel with
pro-Tibetan views. The targets? We’ve seen targets at various
branches of the Taiwanese government as well as a professor at the
Central University Of Tibetan Studies in India.
Taiwan is a logical target since they have
history of accepting Tibetan refugees. Also, the other target is
a professor at the Central University Of Tibetan Studies in India—a
institution founded by the first Prime Minister of India
the Dalai Lama himself. It was established in 1967 to educate
exiled Tibetans and to preserve Tibetan culture and history.
The attackers, called the "Shiqiang gang", show a
consistent modus operandi. They use similar remote
administration tool (RAT) payloads, stolen certificates, and seem to
target anyone pro-Tibetan. The RAT payload in this attack in called
"GrayPigeon," also known as "Huigezi" in
Chinese[2]. It is very popular in the Chinese webspace which indicates
that the attackers speak the language. The RAT payload has multiple
layers of encryption making it harder to identify.
Attack Vector:
The threat arrives in the form of a targeted email with an XLS
attachment. The content of the emails are as shown below in Figure 1
and Figure 2. The email attempts to draw on the sentiments of the
Taiwanese government and activists towards the exiled members of the
Tibetan government.
[caption id="attachment_1707" align="alignnone"
width="584"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_email_1.png"
width="584" height="373" /> Figure 1[/caption]
[caption id="attachment_1708" align="alignnone"
width="590"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_email_2.png"
width="590" height="411" /> Figure 2[/caption]
The content of both the emails are similar and roughly translate to:
Tibetan government-in-exile <<Tibetan government-in-exile offices in the Americas 2013 for the second half the year with detail list requesting for comments>> this is only for friends who care about this participate in our activities in the second half of the year
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Technical Analysis: How the Attack Works
The attached file in both emails is the same (
When opened, the XLS file exploits
and launches a decoy document as shown in Figure 3. The decoy document
contains a ruse as usual and this time it states that Tibetan fonts
are missing. In the background, it drops a series of files eventually
leading to the launch and execution of 2013soft.dll. This in turn
injects a RAT payload in to explorer.exe.
[caption id="attachment_1703" align="alignnone"
width="629"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_attack_flow.png"
width="629" height="486" /> Figure 3[/caption]
Analysis of Payload:
The main functionality lies within 2013soft.dll
(28426ddc3c49635c11a2ee72118e9814) and the subsequent DLL it decrypts
and injects in to explorer.exe (05eda4aaa49b2409f52cf2356f4a91db).
On inspection of 2013soft.dll, it is evident that this payload
contains a rather large resource section. The MAIN stub in resource
section holds large amount of data however it appears to be encrypted.
[caption id="attachment_1710" align="alignnone"
width="648"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_resrouce_section.png"
width="648" height="91" /> Figure 4[/caption]
On dynamic analysis of the payload, it becomes clear that the Main
stub eventually decrypts to the final DLL payload. The stub is loaded
into memory and decrypted using the loop shown in Figure 5. It
operates on 8 bytes of data at a time and uses the 16 bytes key
"1234567890ABCDEF". This, in addition to that fact that it
uses the constant value 0x9E3779B9, gives away the algorithm as
(Tiny encryption algorithm). The TEA algorithm uses this value
as the Delta constant.
[caption id="attachment_1711" align="alignnone"
width="427"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_tea_encryption.png"
width="427" height="371" /> Figure 5[/caption]
It then jumps to the decrypted stub after setting the memory region
it resides in as executable. The start of this decrypted MAIN stub
contains an XOR decryption loop shown in Figure 6. This decryption
loop decrypts the remainder of the stub. Notice how the XOR key
"0x27691C" is only 3 bytes in length but the EAX pointer is
incremented by 4. This means the first byte in every 4 bytes (little
endian) is not subjected to XOR.
[caption id="attachment_1713" align="alignnone"
width="421"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_xor_1.png"
width="421" height="130" /> Figure 6[/caption]
You would think we have the payload after two levels of decryption
but not in this case. It jumps to another shellcode, which performs a
rolling byte XOR decryption using a 4 byte key on the latter part of
the stub.
[caption id="attachment_1714" align="alignnone"
width="465"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_xor_2.png"
width="465" height="175" /> Figure 7[/caption]
Now we are getting somewhere as we can see an MZ file header
interspersed with other characters past the "MinxxxA" marker
as shown in Figure 8. This data is then subjected to what appears to
be a custom decompression algorithm, following which it is injected
into a new instance of explorer.exe
[caption id="attachment_1709" align="alignnone"
width="567"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_m8zp8.png"
width="567" height="481" /> Figure 8[/caption]
The injected DLL payload is a variant of the RAT called "
also known as "Huigezi" which is popular in the Chinese web
space. It is written in Delphi and contains comprehensive
functionality. The RAT uses various Pascal
[3] such as "
and "
also widely seen on Chinese forums and associated with this RAT.
It creates a mutex "\BaseNamedObjects\windows!@#$" and
sets up startup persistence by adding a registry key
"\Software\ts\Explorer\run\2013Soft\run = rundll32.exe
C:\WINDOWS\2013soft.dll,Player". In this case the RAT was
observed key logging and storing the data under
C:\WINDOWS\2013soft.log along with the corresponding Window names.
It then uses the same TEA (Tiny Encryption algorithm) described
earlier to decrypt the address of the command and control server
"help.2012hi.hk". It reuses the key
"1234567890ABCDEF" for TEA decryption. It makes a DNS query
specifically to Google’s DNS server 8.8.8.8 and it attempts to connect
to the resolved server on port 91.
[caption id="attachment_1706" align="alignnone"
width="720"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_dns_query.png"
width="720" height="39" /> Figure 9[/caption]
We observed the following outbound communication on port 91.
[caption id="attachment_1712" align="alignnone"
width="576"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_traffic.png"
width="576" height="92" /> Figure 10[/caption]
This GrayPigeon RAT instance we analyzed had extensive functionality
and a summary of the features is listed below:
Connection to Shiqiang Gang:
We mined for other samples talking to the same C&C
infrastructure and we found two with the md5sums
and 7de5485b7dd154a9bbd85e7d5fcdbdec which drop Hangame RAT and
GrayPigeon RAT respectively. The RAT payloads in these instances also
phone home to help.2012hi.hk. This C&C domain was also referenced
in a white paper published by Symantec as part of the overall campaign
coined the Elderwood project [4]. The campaign in the current instance
and related samples are more in line with Tibetan themed attacks on
NGOs and Taiwanese officials. The campaign also heavily uses stolen
certificates. These have been attributed with the Shiqiang gang as
discussed by Snorre Fagerland from Norman[1] and also discussed by
[5] and AlienVault [6].
[caption id="attachment_1705" align="alignnone"
width="582"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_connection.png"
width="582" height="372" /> Figure 11[/caption]
The decoy document associated with 7de5485b7dd154a9bbd85e7d5fcdbdec
also has a Taiwanese target as evident from the contents of the document.
[caption id="attachment_1704" align="alignnone"
width="791"]
src="https://www.fireeye.com/content/dam/legacy/blog/2013/04/targeted_connection_decoy.png"
width="791" height="365" /> Figure 12[/caption]
Also, both these two variants interestingly have digital
certificates in the payload [1]. The certificate for
is a stolen certificate that has already been revoked.
38:93:f1:3d:d3:9f:e0:88:fd:f5:4e:e0:08:ae:38:e1 sha1WithRSAEncryption 00:00:00 2011 GMT 23:59:59 2012 GMT
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The certificate for 7de5485b7dd154a9bbd85e7d5fcdbdec appears to be modified manually and is invalid.
02:fe:4b:0a:55:23:56:65 sha1WithRSAEncryption Not 10:47:29 2011 GMT
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Hashes of Analyzed Samples:
References:
[2] http://baike.baidu.com/view/25407.htm
[3] http://en.verysource.com/classicgraypigeoncon-191546.html
[4] http://www.symantec.com/connect/blogs/elderwood-project
[5] http://blog.trendmicro.com/trendlabs-security-intelligence/cve-2012-0158-now-being-used-in-more-tibetan-themed-targeted-attack-campaigns/
[6] http://labs.alienvault.com/labs/index.php/2012/cve-2012-0158-tibet-targeted-attacks-and-so-on/
I would like to thank Darien Kindlund for his assistance in research.