The DragonOK group has been actively launching attacks for years. We first discussed them in April 2015 when we witnessed them targeting a number of organizations in Japan. In recent months, Unit 42 has observed a number of attacks that we attribute to this group. Multiple new variants of the previously discussed sysget malware family have been observed in use by DragonOK. Sysget malware was delivered both directly via phishing emails, as well as in Rich Text Format (RTF) documents exploiting the CVE-2015-1641 vulnerability (patched in MS15-033) that in turn leveraged a very unique shellcode. Additionally, we have observed instances of the IsSpace and TidePool malware families being delivered via the same techniques. While Japan is still the most heavily targeted geographic region by this particular actor, we also observed instances where individuals or organizations in Taiwan, Tibet, and Russia also may have been targeted.
We observed two unique techniques of infiltration for this particular campaign:
Phishing emails being sent with malicious executables directly attached
Malicious RTF files which exploit CVE-2015-1641.
The phishing emails had the following characteristics:
Pickup at the Juanda Airport (1-Sep)
ポイントプレゼントのお知らせ [Roughly Translated: Point gift announcement]
20周年記念パーティー [Roughly Translated: 20th Anniversary Party]
参加者の10周年記念同窓会一覧 [Roughly Translated: List of participants’ 10th anniversary alumni association]
子供の調査連れ [Roughly Translated: Children’s investigation]
記念日の再会 [Roughly Translated: Anniversary reunion]
最新の人事異動通知 [Roughly Translated: Recent personnel change notice]
List of Participants.exe
These emails targeted the following industries in Japan:
The malicious RTF files in question leverage a very specific shellcode to drop and execute the malicious payload, as well as a decoy document. Decoy documents are legitimate benign documents that are opened after the malicious payload is delivered, thus ensuring that the victim does not become suspicious because their expected document opened as expected.
Two samples were found to include the decoy document show in Figure 1.
The title of the document roughly translates to “Ministry of Communications & Departments Authorities Empty Sites and Hosted Public Works Source Clearance Photos”. The use of traditional Chinese indicators the target likely residing in either Taiwan, Hong Kong, or Macau. However, based on the Taiwanese subject matter in this document, we can safely come to the conclusion that the intended victim was of Taiwanese origin. These samples delivered an updated version of the IsSpace malware family, which was discussed previously in a watering hole attack targeting an aerospace firm. IsSpace is an evolved variant of the NFlog backdoor, which has been used by DragonOK in the past.
Figure 1 Taiwanese decoy document
Two other samples were identified that used a Tibet-themed decoy document. The document in question (Figure 2) appears to be an internal newsletter from the Central Tibetan Ministry, as suggested by the logo used as well as the content of the document itself. This document indicates that the malware may have been targeted towards an individual that is interested in Tibetan affairs. These particular samples were unique in that they delivered the TidePool malware family that we reported on in May of 2016. We have not previously observed DragonOK using TidePool in attacks.
Figure 2 Tibetan decoy document containing internal newsletter
We also identified an additional sample using decoy targeting Taiwanese victims (Figure 3), which deployed a newer sysget sample.
Figure 3 Taiwanese-targeted decoy document
Other new samples associated with this group used a Russian language decoy document (Figure 4.) The decoy document in question discusses the GOST block cipher, which was created by the Russian government in the 1970’s. The combination of Russian language and Russian-specific subject matter indicates that the intended victim speaks Russian and may be interested in encryption. Like the previously discussed Tibetan decoy documents, these samples also delivered the TidePool malware family.
Figure 4 Russian decoy document discussing the GOST block cipher
Finally, multiple samples used a traditional Chinese language decoy document that discussed a subsidy welfare adjustment program. The use of traditional Chinese indicators the target likely residing in either Taiwan, Hong Kong, or Macau. Similar to other attacks witnessed, a variant of the sysget malware family is installed by these files.
Figure 5 Decoy document discussing subsidy welfare adjustment program
In looking at the various malware samples used in attempted attacks, the following four families were identified:
Sysget version 2
Sysget version 3
We broke the sysget classification into multiple variants when we found that a number of changes have been made since our April 2015 report. Major distinctions between the versions of sysget include the following:
Sysget version 2
Removed support for persistence on Windows XP
Reworked the URIs used for network communication
Added additional layers of encryption for network communication and stored configuration files
Switched from RC4 to AES-128
Sysget version 3
Numerous anti-debug and anti-vm procedures added
Encrypted URIs in network communication with an initial static key
In addition, we observed a sysget version 4 that was discovered in another sample during our research. This version is not attributed to a specific attack against an organization.
Indicators of compromise related to sysget version 4 and other samples not directly attributed to specific attacks may be found in the Appendix of this blog post. Additionally, more information about the various sysget variants may also be found in the Appendix.
The TidePool samples encountered are consistent with the samples previously discussed. I encourage readers to view our previous blog post to learn more about the intricacies of this particular malware family.
The IsSpace malware sample, however, looks to have been updated since last we wrote on it. While the available commands from the command and control (C2) server remains the same, the URI structure of the network communication has been modified. Additionally, the installation routine for this malware family has been updated to be far less complex than previous discussed versions, favoring PowerShell to set persistence and forgoing the previously used side-loading technique. A more detailed analysis of the new instances of IsSpace may be found at the end of this blog post in the Appendix.
A number of unique domains were employed by the various Trojans used in these attacks. For the numerous instances of sysget we observed, the following domains were observed for their C2:
All of the above domains have Chinese
oimage[.]com and trend.gogolekr[.]com are both registered to the same registrant and resolve to the same netblock of 220.127.116.11/24.
The instances of TidePool identified communicated with the following C2 servers:
These domains did not have many definitive relations with the sysget C2 servers except for cool.skywave[.]top, which shared a unique registrant email with the sysget C2 server of trend.gogolekr[.]com. Additionally, the geographic region of the resolved IPs was consistent with the previous set, as they all resolved to various regions in southeast Asia. Specifically, the domains resolved to China, Korea, and Taiwan in the past six months.
The IsSpace samples resolved to the following domains:
These domains had no apparent connections to the previously discussed C2 servers, other than the fact that they resolved to Korea and Hong Kong respectively. Additionally, the registrar of ‘Jiangsu Bangning Science and technology Co. Ltd.’ was used for a large number of domains. A full graph of the relations between the various attacks is shown in Figure 6.
Figure 6 Relationships between attacks
The DragonOK group are quite active and continue updating their tools and tactics. Their toolset is being actively developed to make detection and analysis more difficult. Additionally, they appear to be using additional malware toolsets such as TidePool. While Japan is still the most-targeted region by this group, they look to be seeking out victims in other regions as well, such as Taiwan, Tibet, and Russia.
Palo Alto Network customers are protected against this threat in the following ways:
Malware families are tagged in AutoFocus via a variety of tags (TidePool, NFlog, Sysget)
The following IPS signatures detect malicious network traffic:
IPS signature 14365 (IsSpace.Gen Command And Control Traffic)
IPS signature 14588 (Suspicious.Gen Command And Control Traffic)
IPS signature 13574 (NfLog.Gen Command And Control Traffic)
IPS signature 13359 (Nflog.Gen Command And Control Traffic)
All samples are appropriately marked malicious in WildFire.
Article by Josh Grunzweig, Unit 42, Palo Alto Networks.