Article Content Author: Dell SecureWorks Counter Threat Unit™ Threat Intelligence Date: August 5, 2015   Summary  Dell SecureWorks Counter Threat Unit(TM) (CTU) researchers investigated activities associated with Threat Group-3390[1] (TG-3390) Analysis of TG-3390's operations, targeting, and tools led CTU researchers to assess with moderate confidence the group is located in the People's Republic of China The threat actors target a wide range of organizations: CTU researchers have observed TG-3390 actors obtaining confidential data on defense manufacturing projects, but also targeting other industry verticals and attacking organizations involved in international relations The group extensively uses long-running strategic web compromises[2] (SWCs), and relies on whitelists to deliver payloads to select victims In comparison to other threat groups, TG-3390 is notable for its tendency to compromise Microsoft Exchange servers using a custom backdoor and credential logger CTU researchers divided the threat intelligence about TG-3390 into two sections: strategic and tactical Strategic threat intelligence includes an assessment of the ongoing threat posed by the threat group Executives can use this assessment to determine how to reduce risk to their organization's mission and critical assets Tactical threat intelligence is based on incident response investigations and research, and is mapped to the kill chain Computer network defenders can use this information to reduce the time and effort associated with responding to TG-3390 Key points Explanations of how CTU researchers identify attribution and gauge confidence levels are available in the Appendix A CTU researchers assess with moderate confidence that TG-3390 is based in the People's Republic of China CTU researchers have evidence that the threat group compromised U.S and UK organizations in the following verticals: manufacturing (specifically aerospace (including defense contractors), automotive, technology, energy, and pharmaceuticals), education, and legal, as well as organizations focused on international relations Based on analysis of the group's SWCs, TG-3390 operations likely affect organizations in other countries and verticals TG-3390 operates a broad and long-running campaign of SWCs and has compromised approximately 100 websites as of this publication Through an IP address whitelisting process, the threat group selectively targets visitors to these websites After the initial compromise, TG-3390 delivers the HttpBrowser backdoor to its victims The threat actors then move quickly to compromise Microsoft Exchange servers and to gain complete control of the target environment The threat actors are adept at identifying key data stores and selectively exfiltrating all of the high-value information associated with their goal CTU researchers recommend the following practices to prevent or detect TG-3390 intrusions:  Search web log files for evidence of web server scanning using the URIs listed in the Exploitation section and evidence of exfiltration using the User-Agent in the Actions on objective section Require two-factor authentication for all remote access solutions, including OWA Strategic threat intelligence CTU researchers assess the threat posed by a threat group by reviewing intent and capability (see Figure 1) Threat groups pose varying threats to different organizations, and even a very capable group may pose a low threat if it does not have the intent to target a particular organization Figure 1 Threat is based on a threat group's intent and capability (Source: Dell SecureWorks) Intent CTU researchers infer intent by aggregating observations, analyzing a threat group's activity, and placing the information in a wider context CTU researchers assess with high confidence that TG-3390 uses information gathered from prior reconnaissance activities to selectively compromise users who visit websites under its control Most websites compromised by TG-3390 actors are affiliated with five types of organizations around the world:  large manufacturing companies, particularly those supplying defense organizations energy companies embassies in Washington, DC representing countries in the Middle East, Europe, and Asia, likely to target U.S.-based users involved in international relations non-governmental organizations (NGOs), particularly those focused on international relations and defense government organizations  Based on this information, CTU researchers assess that TG-3390 aims to collect defense technology and capability intelligence, other industrial intelligence, and political intelligence from governments and NGOs Attribution To assess attribution, CTU researchers analyze observed activity, third-party reporting, and contextual intelligence For the following reasons, CTU researchers assess with moderate confidence that TG-3390 has a Chinese nexus:  The SWC of a Uyghur cultural website suggests intent to target the Uyghur ethnic group, a Muslim minority group primarily found in the Xinjiang region of China Threat groups outside of China are unlikely to target the Uyghur people TG-3390 uses the PlugX remote access tool The menus for PlugX's server-side component are written exclusively in Standard Chinese (Mandarin), suggesting that PlugX operators are familiar with this language CTU researchers have observed TG-3390 activity between 04:00 and 09:00 UTC, which is 12:00 to 17:00 local time in China (UTC +8) The timeframe maps to the second half of the workday in China The threat actors have used the Baidu search engine, which is only available in Chinese, to conduct reconnaissance activities CTU researchers have observed the threat group obtaining information about specific U.S defense projects that would be desirable to those operating within a country with a manufacturing base, an interest in U.S military capability, or both CTU researchers recognize that the evidence supporting this attribution is circumstantial It is possible that TG-3390 is false-flag operation by a threat group outside of China that is deliberately planting indications of a Chinese origin Capability To assess a threat group's capability, CTU researchers analyze its resources, technical proficiency, and tradecraft Resources TG-3390 has access to proprietary tools, some of which are used exclusively by TG-3390 and others that are shared among a few Chinese threat groups The complexity and continual development of these tools indicates a mature development process TG-3390 can quickly leverage compromised network infrastructure during an operation and can conduct simultaneous intrusions into multiple environments This ability is further demonstrated by analysis of interactions between TG-3390 operators and a target environment CTU researchers found no evidence of multiple operators working simultaneously against a single organization This efficiency of operation (a 1:1 ratio of operator to observed activity) suggests that TG-3390 can scale to conduct the maximum number of simultaneous operations These characteristics suggest that the threat group is well resourced and has access to a tools development team and a team focused on SWCs Technical proficiency TG-3390's obfuscation techniques in SWCs complicate detection of malicious web traffic redirects Malware used by the threat group can be configured to bypass network-based detection; however, the threat actors rarely modify host-based configuration settings when deploying payloads CTU researchers have observed the threat actors installing a credential logger and backdoor on Microsoft Exchange servers, which requires a technical grasp of Internet Information Services (IIS) TG-3390 uses older exploits to compromise targets, and CTU researchers have not observed the threat actors using zero-day exploits as of this publication The threat actors demonstrated the ability to adapt when reentering a network after an eviction, overcoming technical barriers constructed by network defenders Tradecraft In addition to using SWCs to target specific types of organizations, TG-3390 uses spearphishing emails to target specific victims CTU researchers assess with high confidence that the threat actors follow an established playbook during an intrusion They quickly move away from their initial access vector to hide their entry point and then target Exchange servers as a new access vector As of this publication, CTU researchers have not discovered how TG-3390 keeps track of the details associated with its compromised assets and credentials However, the threat actors' ability to reuse these assets and credentials, sometimes weeks or months after the initial compromise, indicates the group is disciplined and well organized After gaining access to a target network in one intrusion analyzed by CTU researchers, TG-3390 actors identified and exfiltrated data for specific projects run by the target organization, indicating that they successfully obtained the information they sought Data exfiltration occurred almost four weeks after the initial compromise and continued for two weeks (see Figure 2) Figure 2 Data exfiltration timeline (Source: Dell SecureWorks)    Note: The adversary's end goal is to exfiltrate, not infiltrate Organizations often miss multiple opportunities to detect and disrupt the threat actors before they can achieve their objective Tactical threat intelligence Known tools CTU researchers have observed TG-3390 actors using tools that are favored by multiple threat groups:  PlugX — A remote access tool notable for communications that may contain HTTP headers starting with "X-" (e.g., "X-Session: 0") The malware can be configured to use multiple network protocols to avoid network-based detection HttpBrowser (also known as TokenControl) — A backdoor notable for HTTPS communications with the HttpBrowser/1.0 User-Agent (see Figure 3) Antivirus detection for HttpBrowser is extremely low and is typically based upon heuristic signatures More information about HttpBrowser is available in Appendix B Figure 3 HttpBrowser URI Figure 4 Hunter — A web application scanning tool written by @tojen to identify vulnerabilities in Apache Tomcat, Red Hat JBoss Middleware, and Adobe ColdFusion (see Figure 5) It can also identify open ports, collect web banners, and download secondary files Figure 5 Hunter usage It is installed as an ISAPI filter Captured credentials are DES-encrypted using the password "12345678" and are written to the log.txt file in the root directory It is deployed to internally accessible servers running Internet Information Services (IIS) Figure 6 Reconnaissance CTU researchers have not observed TG-3390 actors performing reconnaissance prior to compromising organizations As discussed in the Actions on objectives section, the threat actors appear to wait until they have established a foothold Development TG-3390 actors use command and control (C2) domains for extended periods of time but frequently change the domains' IP addresses The new IP addresses are typically on the same subnet as the previous ones TG-3390 is capable of using a C2 infrastructure that spans multiple networks and registrars The most common registrar used by the adversary is HiChina Zhicheng Technology Ltd The threat actors have a demonstrated ability to move from one network provider to another, using some infrastructure for extended periods of time and other domains for only a few days Seemingly random activity patterns in infrastructure deployment and usage, along with the ability to use a wide variety of geographically diverse infrastructure, help the threat actors avoid detection TG-3390 SWCs may be largely geographically independent, but the group's most frequently used C2 registrars and IP net blocks are located in the U.S Using a U.S.-based C2 infrastructure (see Figure 7) to compromise targets in the U.S helps TG-3390 actors avoid geo-blocking and geo-flagging measures used in network defense Figure 7 Geolocation of TG-3390 infrastructure observed by CTU researchers The dark green signifies a high count of C2 registrars and IP net blocks, while the light green represents a smaller count (Source: Dell SecureWorks) The threat actors create PlugX DLL stub loaders that will run only after a specific date The compile dates of the samples analyzed by CTU researchers are all later than the hard-coded August 8, 2013 date, indicating that the code might be reused from previous tools Weaponization As of this publication, CTU researchers are unsure if TG-3390 relies on weaponizers to package tools and exploits The ZIP archives have names relevant to the targets and contain both legitimate files and malware Figure 8 Decoy image Figure 9 SWC code Figure 10 Unpacked JavaScript code The threat actors have evolved to whitelisting IP addresses and only delivering the exploit and payload to specific targets of interest CTU researchers have observed TG-3390 compromising a target organization's externally and internally accessible assets, such as an OWA server, and adding redirect code to point internal users to an external website that hosts an exploit and delivers malware Exploitation TG-3390 actors have used Java exploits in their SWCs In activity analyzed by CTU researchers, TG-3390 executed the Hunter web application scanning tool against a target server running IIS CTU researchers have observed the threat actors employing legitimate Kaspersky antivirus variants in analyzed samples The DLL acts as a stub loader, which loads and executes the shell code The adversaries have used this technique to allow PlugX and HttpBrowser to persist on a system The challenge is detecting known good software loading and running malware The IIS w3wp.exe process loads the malicious DLL, which CTU researchers have observed in the Program Files\Microsoft\Exchange Server\ClientAccess\Owa\Bin directory The PlugX malware can be configured to use HTTP, DNS, raw TCP, or UDP to avoid network-based detection In one sample analyzed by CTU researchers, PlugX was configured with hard-coded user credentials to bypass a proxy that required authentication When the adversaries' operations are live, they modify the record again to point the C2 domain to an IP address they can access A domain name parking example is available in Appendix D Actions on objective CTU researchers have discovered numerous details about TG-3390 operations, including how the adversaries explore a network, move laterally, and exfiltrate data Within six hours of entering the environment, the threat actors compromised multiple systems and stole credentials for the entire domain Figure 11 Timeline, in Eastern Time, of TG-3390's initial entry into a victim's network (Source: Dell SecureWorks) The threat actors use the Hunter and nbtscan tools, sometimes renamed, to conduct network reconnaissance for vulnerable servers and online systems (see Figure 12) Figure 12 nbtscan batch script (renamed ipcan.exe) used to profile network CTU researchers observed the threat actors collecting Cisco VPN profiles to use when accessing the victim's network via VPN (see Figure 13) Figure 13 Copying of .pcf files CTU researchers have observed the threat actors encrypting data using the password "admin-windows2014" and splitting the RAR archives into parts in the recycler directory, with the same name as the uncompressed data (see Figure 14) Figure 14 Batch script used to archive data (Source: Dell SecureWorks) The number at the end of the password corresponds to the year of the intrusion For example, the password "admin-windows2014" shown in Figure 14 was changed to "admin-windows2015" for TG-3390 intrusions conducted in 2015 In some instances, adversaries exceed disk space limits during the exfiltration process, requiring the staging of archives on multiple systems Unexplained disk quota alerts on typically underutilized systems warrants immediate investigation Figure 15 Batch script used to rename exfiltrated data (Source: Dell SecureWorks) CTU researchers have observed TG-3390 actors staging RAR archives, renamed with a .zip file extension, on externally accessible web servers The adversaries then issue HTTP GET requests, sometimes with the User-Agent MINIXL, to exfiltrate the archive parts from the victim's network (see Figure 16) Figure 16 Example GET request from IIS log (Source: Dell SecureWorks) In other intrusions, data was exfiltrated using the PlugX remote access tool Figure 17 shows network data transfer sizes for a month-long period beginning with TG-3390's re-entry into a network Approximately 300 GB of data was exfiltrated during that span Figure 17 Network data transfer sizes to C2 servers after TG-3390 reentry into a network (Source: Dell SecureWorks) CTU observations Figure 18 is a UTC time wheel depicting which hours the threat actors actively operated in one target environment during a three-day intrusion observed by CTU researchers The concentric bands represent the days of the week, with Saturday as the outside band and Sunday as the innermost band, and each cell represents an hour The darker the cell color, the higher the activity level; white indicates no observed activity TG-3390 was most active between 04:00 and 09:00 UTC Figure 18 The legend across the bottom of the figure lists the upper bound of interactions that are represented by each color variation on the wheel Times are based on UTC (Source: Dell SecureWorks) Response to eviction Successfully evicting TG-3390 from an environment requires a coordinated plan to remove all access points, including remote access tools and web shells Within weeks of eviction, the threat actors attempt to access their ChinaChopper web shells from previously used IP addresses Finding the web shells inaccessible, the adversaries search google.co.jp for remote access solutions CTU researchers discovered the threat actors searching for "[company] login," which directed them to the landing page for remote access CTU researchers believe legitimate websites are used to host tools because web proxies categorize the sites as benign Note: Numerous threat groups use legitimate remote access solutions (VPN, Citrix, OWA, etc.) to enter or reenter a network After executing an eviction plan, it is paramount to reset all credentials, including those for third-party accounts, preferably after implementing two-factor authentication After reentering an environment, the threat actors focus on obtaining the active directory contents Figure 19 shows a timeline of TG-3390 attempting to regain a foothold in a network in a span of only five hours Figure 19 Timeline, in Eastern Time, of TG-3390's reentry into a compromised network (Source: Dell SecureWorks)     Note: Relying primarily on network-based security controls will not deter most threat groups from achieving their objective Adversaries can overcome blacklisted infrastructure in minutes, as TG-3390 actors did when they staged tools on compromised web servers Figure 20 Figure 21 (Source: Dell SecureWorks) CTU researchers have no evidence to determine if these tools are also used by TG-3390 Conclusion TG-3390 is known for compromising organizations via SWCs and moving quickly to install backdoors on Exchange servers Despite the group's proficiency, there are still many opportunities to detect and disrupt its operation by studying its modus operandi The threat actors work to overcome existing security controls, or those put in place during an engagement, to complete their mission of exfiltrating intellectual property Due to TG-3390's determination, organizations should formulate a solid eviction plan before engaging with the threat actors to prevent them from reentering the network Threat indicators The indicators in Table 1 are associated with TG-3390 activity The domains and IP addresses may contain malicious content, so consider the risks before opening them in a browser TG-3390 indicators Appendix A — Identifying attribution and gauging confidence Identifying attribution In most cases, CTU researchers not have intelligence to directly attribute a threat group, so attribution relies on circumstantial evidence and is an assessment rather than a fact CTU researchers draw on three distinct intelligence bases for evidence of attribution:  Observed activity is gathered from CTU researchers' observation and investigation of a threat group's activity on a target network and across Dell SecureWorks data, and analysis of tactics, techniques, and procedures (TTPs) the threat group employs Third-party intelligence is gained from trusted relationships within the security industry and with other private and public sector organizations, as well as analysis of open source intelligence Contextual analysis compares threat group targets against intelligence requirements of nation states and other threat actors and compares tradecraft employed by a threat group to tradecraft of known threat actors Gauging confidence level CTU researchers have adopted the grading system published by the U.S Office of the Director of National Intelligence to indicate confidence in their assessments:  High confidence generally indicates that judgments are based on high-quality information, and/or that the nature of the issue makes it possible to render a solid judgment A "high confidence" judgment is not a fact or a certainty, however, and such judgments still carry a risk of being wrong Moderate confidence generally means that the information is credibly sourced and plausible but not of sufficient quality or corroborated sufficiently to warrant a higher level of confidence Appendix B — HttpBrowser analysis HttpBrowser is a remote access tool whose name originates from the hard-coded "HttpBrowser/1.0" User-Agent CTU researchers also identified a PDB string in the binaries, J:\TokenControlV3\ServerDll\Release\ServerDll.pdb, which implies that the threat actors may refer to the tool as "TokenControl." Table 2 lists the commands available to threat actors in one of the HttpBrowser variants HttpBrowser command set (Source: Dell SecureWorks) Other variants of the backdoor may include additional commands such as setcmd, settime, uninstall, and down Table 3 shows the unencrypted URL parameters, along with sample data and a description of the data HttpBrowser parameters Like ChinaChopper, it parses HTTP requests for the Z1 and Z2 parameters (see Table 4) In addition to acting as a web shell, the malware captures and DES-encrypts credentials before writing the username and password to disk The DES key to encrypt the credentials in the configuration observed by CTU researchers is 12345678, and the log file is c:\log.txt Figure 22 Table 5 demonstrates how the threat actors change one of their C2 domains to point to routable and non-routable IP addresses over time Start date End date IP change Location   7/9/13 7/31/13 210.116.106.66 Seoul, Korea   7/31/13 10/12/13 127.0.0.1 N/A   10/12/13 11/5/13 122.10.10.196 Hong Kong   11/5/13 1/12/14 198.100.107.107 California, U.S Example parking of trendmicro-update org (Source: Dell SecureWorks) Endnotes [1] The Dell SecureWorks Counter Threat Unit(TM) (CTU) research team tracks threat groups by assigning them four-digit randomized numbers (3390 in this case), and compiles information from first-hand incident response observations and from external sources Visitors to the compromised website are redirected to a server under the threat group's control, where their system is compromised with the threat group's malware With this tactic, a threat group increases the likelihood of compromising systems that possess desired information 
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request. ### Instruction: List the MITRE techniques contained in the text. ### Input: Article Content Author: Dell SecureWorks Counter Threat Unit™ Threat Intelligence Date: August 5, 2015   Summary  Dell SecureWorks Counter Threat Unit(TM) (CTU) researchers investigated activities associated with Threat Group-3390[1] (TG-3390) Analysis of TG-3390's operations, targeting, and tools led CTU researchers to assess with moderate confidence the group is located in the People's Republic of China The threat actors target a wide range of organizations: CTU researchers have observed TG-3390 actors obtaining confidential data on defense manufacturing projects, but also targeting other industry verticals and attacking organizations involved in international relations The group extensively uses long-running strategic web compromises[2] (SWCs), and relies on whitelists to deliver payloads to select victims In comparison to other threat groups, TG-3390 is notable for its tendency to compromise Microsoft Exchange servers using a custom backdoor and credential logger CTU researchers divided the threat intelligence about TG-3390 into two sections: strategic and tactical Strategic threat intelligence includes an assessment of the ongoing threat posed by the threat group Executives can use this assessment to determine how to reduce risk to their organization's mission and critical assets Tactical threat intelligence is based on incident response investigations and research, and is mapped to the kill chain Computer network defenders can use this information to reduce the time and effort associated with responding to TG-3390 Key points Explanations of how CTU researchers identify attribution and gauge confidence levels are available in the Appendix A CTU researchers assess with moderate confidence that TG-3390 is based in the People's Republic of China CTU researchers have evidence that the threat group compromised U.S and UK organizations in the following verticals: manufacturing (specifically aerospace (including defense contractors), automotive, technology, energy, and pharmaceuticals), education, and legal, as well as organizations focused on international relations Based on analysis of the group's SWCs, TG-3390 operations likely affect organizations in other countries and verticals TG-3390 operates a broad and long-running campaign of SWCs and has compromised approximately 100 websites as of this publication Through an IP address whitelisting process, the threat group selectively targets visitors to these websites After the initial compromise, TG-3390 delivers the HttpBrowser backdoor to its victims The threat actors then move quickly to compromise Microsoft Exchange servers and to gain complete control of the target environment The threat actors are adept at identifying key data stores and selectively exfiltrating all of the high-value information associated with their goal CTU researchers recommend the following practices to prevent or detect TG-3390 intrusions:  Search web log files for evidence of web server scanning using the URIs listed in the Exploitation section and evidence of exfiltration using the User-Agent in the Actions on objective section Require two-factor authentication for all remote access solutions, including OWA Strategic threat intelligence CTU researchers assess the threat posed by a threat group by reviewing intent and capability (see Figure 1) Threat groups pose varying threats to different organizations, and even a very capable group may pose a low threat if it does not have the intent to target a particular organization Figure 1 Threat is based on a threat group's intent and capability (Source: Dell SecureWorks) Intent CTU researchers infer intent by aggregating observations, analyzing a threat group's activity, and placing the information in a wider context CTU researchers assess with high confidence that TG-3390 uses information gathered from prior reconnaissance activities to selectively compromise users who visit websites under its control Most websites compromised by TG-3390 actors are affiliated with five types of organizations around the world:  large manufacturing companies, particularly those supplying defense organizations energy companies embassies in Washington, DC representing countries in the Middle East, Europe, and Asia, likely to target U.S.-based users involved in international relations non-governmental organizations (NGOs), particularly those focused on international relations and defense government organizations  Based on this information, CTU researchers assess that TG-3390 aims to collect defense technology and capability intelligence, other industrial intelligence, and political intelligence from governments and NGOs Attribution To assess attribution, CTU researchers analyze observed activity, third-party reporting, and contextual intelligence For the following reasons, CTU researchers assess with moderate confidence that TG-3390 has a Chinese nexus:  The SWC of a Uyghur cultural website suggests intent to target the Uyghur ethnic group, a Muslim minority group primarily found in the Xinjiang region of China Threat groups outside of China are unlikely to target the Uyghur people TG-3390 uses the PlugX remote access tool The menus for PlugX's server-side component are written exclusively in Standard Chinese (Mandarin), suggesting that PlugX operators are familiar with this language CTU researchers have observed TG-3390 activity between 04:00 and 09:00 UTC, which is 12:00 to 17:00 local time in China (UTC +8) The timeframe maps to the second half of the workday in China The threat actors have used the Baidu search engine, which is only available in Chinese, to conduct reconnaissance activities CTU researchers have observed the threat group obtaining information about specific U.S defense projects that would be desirable to those operating within a country with a manufacturing base, an interest in U.S military capability, or both CTU researchers recognize that the evidence supporting this attribution is circumstantial It is possible that TG-3390 is false-flag operation by a threat group outside of China that is deliberately planting indications of a Chinese origin Capability To assess a threat group's capability, CTU researchers analyze its resources, technical proficiency, and tradecraft Resources TG-3390 has access to proprietary tools, some of which are used exclusively by TG-3390 and others that are shared among a few Chinese threat groups The complexity and continual development of these tools indicates a mature development process TG-3390 can quickly leverage compromised network infrastructure during an operation and can conduct simultaneous intrusions into multiple environments This ability is further demonstrated by analysis of interactions between TG-3390 operators and a target environment CTU researchers found no evidence of multiple operators working simultaneously against a single organization This efficiency of operation (a 1:1 ratio of operator to observed activity) suggests that TG-3390 can scale to conduct the maximum number of simultaneous operations These characteristics suggest that the threat group is well resourced and has access to a tools development team and a team focused on SWCs Technical proficiency TG-3390's obfuscation techniques in SWCs complicate detection of malicious web traffic redirects Malware used by the threat group can be configured to bypass network-based detection; however, the threat actors rarely modify host-based configuration settings when deploying payloads CTU researchers have observed the threat actors installing a credential logger and backdoor on Microsoft Exchange servers, which requires a technical grasp of Internet Information Services (IIS) TG-3390 uses older exploits to compromise targets, and CTU researchers have not observed the threat actors using zero-day exploits as of this publication The threat actors demonstrated the ability to adapt when reentering a network after an eviction, overcoming technical barriers constructed by network defenders Tradecraft In addition to using SWCs to target specific types of organizations, TG-3390 uses spearphishing emails to target specific victims CTU researchers assess with high confidence that the threat actors follow an established playbook during an intrusion They quickly move away from their initial access vector to hide their entry point and then target Exchange servers as a new access vector As of this publication, CTU researchers have not discovered how TG-3390 keeps track of the details associated with its compromised assets and credentials However, the threat actors' ability to reuse these assets and credentials, sometimes weeks or months after the initial compromise, indicates the group is disciplined and well organized After gaining access to a target network in one intrusion analyzed by CTU researchers, TG-3390 actors identified and exfiltrated data for specific projects run by the target organization, indicating that they successfully obtained the information they sought Data exfiltration occurred almost four weeks after the initial compromise and continued for two weeks (see Figure 2) Figure 2 Data exfiltration timeline (Source: Dell SecureWorks)    Note: The adversary's end goal is to exfiltrate, not infiltrate Organizations often miss multiple opportunities to detect and disrupt the threat actors before they can achieve their objective Tactical threat intelligence Known tools CTU researchers have observed TG-3390 actors using tools that are favored by multiple threat groups:  PlugX — A remote access tool notable for communications that may contain HTTP headers starting with "X-" (e.g., "X-Session: 0") The malware can be configured to use multiple network protocols to avoid network-based detection HttpBrowser (also known as TokenControl) — A backdoor notable for HTTPS communications with the HttpBrowser/1.0 User-Agent (see Figure 3) Antivirus detection for HttpBrowser is extremely low and is typically based upon heuristic signatures More information about HttpBrowser is available in Appendix B Figure 3 HttpBrowser URI Figure 4 Hunter — A web application scanning tool written by @tojen to identify vulnerabilities in Apache Tomcat, Red Hat JBoss Middleware, and Adobe ColdFusion (see Figure 5) It can also identify open ports, collect web banners, and download secondary files Figure 5 Hunter usage It is installed as an ISAPI filter Captured credentials are DES-encrypted using the password "12345678" and are written to the log.txt file in the root directory It is deployed to internally accessible servers running Internet Information Services (IIS) Figure 6 Reconnaissance CTU researchers have not observed TG-3390 actors performing reconnaissance prior to compromising organizations As discussed in the Actions on objectives section, the threat actors appear to wait until they have established a foothold Development TG-3390 actors use command and control (C2) domains for extended periods of time but frequently change the domains' IP addresses The new IP addresses are typically on the same subnet as the previous ones TG-3390 is capable of using a C2 infrastructure that spans multiple networks and registrars The most common registrar used by the adversary is HiChina Zhicheng Technology Ltd The threat actors have a demonstrated ability to move from one network provider to another, using some infrastructure for extended periods of time and other domains for only a few days Seemingly random activity patterns in infrastructure deployment and usage, along with the ability to use a wide variety of geographically diverse infrastructure, help the threat actors avoid detection TG-3390 SWCs may be largely geographically independent, but the group's most frequently used C2 registrars and IP net blocks are located in the U.S Using a U.S.-based C2 infrastructure (see Figure 7) to compromise targets in the U.S helps TG-3390 actors avoid geo-blocking and geo-flagging measures used in network defense Figure 7 Geolocation of TG-3390 infrastructure observed by CTU researchers The dark green signifies a high count of C2 registrars and IP net blocks, while the light green represents a smaller count (Source: Dell SecureWorks) The threat actors create PlugX DLL stub loaders that will run only after a specific date The compile dates of the samples analyzed by CTU researchers are all later than the hard-coded August 8, 2013 date, indicating that the code might be reused from previous tools Weaponization As of this publication, CTU researchers are unsure if TG-3390 relies on weaponizers to package tools and exploits The ZIP archives have names relevant to the targets and contain both legitimate files and malware Figure 8 Decoy image Figure 9 SWC code Figure 10 Unpacked JavaScript code The threat actors have evolved to whitelisting IP addresses and only delivering the exploit and payload to specific targets of interest CTU researchers have observed TG-3390 compromising a target organization's externally and internally accessible assets, such as an OWA server, and adding redirect code to point internal users to an external website that hosts an exploit and delivers malware Exploitation TG-3390 actors have used Java exploits in their SWCs In activity analyzed by CTU researchers, TG-3390 executed the Hunter web application scanning tool against a target server running IIS CTU researchers have observed the threat actors employing legitimate Kaspersky antivirus variants in analyzed samples The DLL acts as a stub loader, which loads and executes the shell code The adversaries have used this technique to allow PlugX and HttpBrowser to persist on a system The challenge is detecting known good software loading and running malware The IIS w3wp.exe process loads the malicious DLL, which CTU researchers have observed in the Program Files\Microsoft\Exchange Server\ClientAccess\Owa\Bin directory The PlugX malware can be configured to use HTTP, DNS, raw TCP, or UDP to avoid network-based detection In one sample analyzed by CTU researchers, PlugX was configured with hard-coded user credentials to bypass a proxy that required authentication When the adversaries' operations are live, they modify the record again to point the C2 domain to an IP address they can access A domain name parking example is available in Appendix D Actions on objective CTU researchers have discovered numerous details about TG-3390 operations, including how the adversaries explore a network, move laterally, and exfiltrate data Within six hours of entering the environment, the threat actors compromised multiple systems and stole credentials for the entire domain Figure 11 Timeline, in Eastern Time, of TG-3390's initial entry into a victim's network (Source: Dell SecureWorks) The threat actors use the Hunter and nbtscan tools, sometimes renamed, to conduct network reconnaissance for vulnerable servers and online systems (see Figure 12) Figure 12 nbtscan batch script (renamed ipcan.exe) used to profile network CTU researchers observed the threat actors collecting Cisco VPN profiles to use when accessing the victim's network via VPN (see Figure 13) Figure 13 Copying of .pcf files CTU researchers have observed the threat actors encrypting data using the password "admin-windows2014" and splitting the RAR archives into parts in the recycler directory, with the same name as the uncompressed data (see Figure 14) Figure 14 Batch script used to archive data (Source: Dell SecureWorks) The number at the end of the password corresponds to the year of the intrusion For example, the password "admin-windows2014" shown in Figure 14 was changed to "admin-windows2015" for TG-3390 intrusions conducted in 2015 In some instances, adversaries exceed disk space limits during the exfiltration process, requiring the staging of archives on multiple systems Unexplained disk quota alerts on typically underutilized systems warrants immediate investigation Figure 15 Batch script used to rename exfiltrated data (Source: Dell SecureWorks) CTU researchers have observed TG-3390 actors staging RAR archives, renamed with a .zip file extension, on externally accessible web servers The adversaries then issue HTTP GET requests, sometimes with the User-Agent MINIXL, to exfiltrate the archive parts from the victim's network (see Figure 16) Figure 16 Example GET request from IIS log (Source: Dell SecureWorks) In other intrusions, data was exfiltrated using the PlugX remote access tool Figure 17 shows network data transfer sizes for a month-long period beginning with TG-3390's re-entry into a network Approximately 300 GB of data was exfiltrated during that span Figure 17 Network data transfer sizes to C2 servers after TG-3390 reentry into a network (Source: Dell SecureWorks) CTU observations Figure 18 is a UTC time wheel depicting which hours the threat actors actively operated in one target environment during a three-day intrusion observed by CTU researchers The concentric bands represent the days of the week, with Saturday as the outside band and Sunday as the innermost band, and each cell represents an hour The darker the cell color, the higher the activity level; white indicates no observed activity TG-3390 was most active between 04:00 and 09:00 UTC Figure 18 The legend across the bottom of the figure lists the upper bound of interactions that are represented by each color variation on the wheel Times are based on UTC (Source: Dell SecureWorks) Response to eviction Successfully evicting TG-3390 from an environment requires a coordinated plan to remove all access points, including remote access tools and web shells Within weeks of eviction, the threat actors attempt to access their ChinaChopper web shells from previously used IP addresses Finding the web shells inaccessible, the adversaries search google.co.jp for remote access solutions CTU researchers discovered the threat actors searching for "[company] login," which directed them to the landing page for remote access CTU researchers believe legitimate websites are used to host tools because web proxies categorize the sites as benign Note: Numerous threat groups use legitimate remote access solutions (VPN, Citrix, OWA, etc.) to enter or reenter a network After executing an eviction plan, it is paramount to reset all credentials, including those for third-party accounts, preferably after implementing two-factor authentication After reentering an environment, the threat actors focus on obtaining the active directory contents Figure 19 shows a timeline of TG-3390 attempting to regain a foothold in a network in a span of only five hours Figure 19 Timeline, in Eastern Time, of TG-3390's reentry into a compromised network (Source: Dell SecureWorks)     Note: Relying primarily on network-based security controls will not deter most threat groups from achieving their objective Adversaries can overcome blacklisted infrastructure in minutes, as TG-3390 actors did when they staged tools on compromised web servers Figure 20 Figure 21 (Source: Dell SecureWorks) CTU researchers have no evidence to determine if these tools are also used by TG-3390 Conclusion TG-3390 is known for compromising organizations via SWCs and moving quickly to install backdoors on Exchange servers Despite the group's proficiency, there are still many opportunities to detect and disrupt its operation by studying its modus operandi The threat actors work to overcome existing security controls, or those put in place during an engagement, to complete their mission of exfiltrating intellectual property Due to TG-3390's determination, organizations should formulate a solid eviction plan before engaging with the threat actors to prevent them from reentering the network Threat indicators The indicators in Table 1 are associated with TG-3390 activity The domains and IP addresses may contain malicious content, so consider the risks before opening them in a browser TG-3390 indicators Appendix A — Identifying attribution and gauging confidence Identifying attribution In most cases, CTU researchers not have intelligence to directly attribute a threat group, so attribution relies on circumstantial evidence and is an assessment rather than a fact CTU researchers draw on three distinct intelligence bases for evidence of attribution:  Observed activity is gathered from CTU researchers' observation and investigation of a threat group's activity on a target network and across Dell SecureWorks data, and analysis of tactics, techniques, and procedures (TTPs) the threat group employs Third-party intelligence is gained from trusted relationships within the security industry and with other private and public sector organizations, as well as analysis of open source intelligence Contextual analysis compares threat group targets against intelligence requirements of nation states and other threat actors and compares tradecraft employed by a threat group to tradecraft of known threat actors Gauging confidence level CTU researchers have adopted the grading system published by the U.S Office of the Director of National Intelligence to indicate confidence in their assessments:  High confidence generally indicates that judgments are based on high-quality information, and/or that the nature of the issue makes it possible to render a solid judgment A "high confidence" judgment is not a fact or a certainty, however, and such judgments still carry a risk of being wrong Moderate confidence generally means that the information is credibly sourced and plausible but not of sufficient quality or corroborated sufficiently to warrant a higher level of confidence Appendix B — HttpBrowser analysis HttpBrowser is a remote access tool whose name originates from the hard-coded "HttpBrowser/1.0" User-Agent CTU researchers also identified a PDB string in the binaries, J:\TokenControlV3\ServerDll\Release\ServerDll.pdb, which implies that the threat actors may refer to the tool as "TokenControl." Table 2 lists the commands available to threat actors in one of the HttpBrowser variants HttpBrowser command set (Source: Dell SecureWorks) Other variants of the backdoor may include additional commands such as setcmd, settime, uninstall, and down Table 3 shows the unencrypted URL parameters, along with sample data and a description of the data HttpBrowser parameters Like ChinaChopper, it parses HTTP requests for the Z1 and Z2 parameters (see Table 4) In addition to acting as a web shell, the malware captures and DES-encrypts credentials before writing the username and password to disk The DES key to encrypt the credentials in the configuration observed by CTU researchers is 12345678, and the log file is c:\log.txt Figure 22 Table 5 demonstrates how the threat actors change one of their C2 domains to point to routable and non-routable IP addresses over time Start date End date IP change Location   7/9/13 7/31/13 210.116.106.66 Seoul, Korea   7/31/13 10/12/13 127.0.0.1 N/A   10/12/13 11/5/13 122.10.10.196 Hong Kong   11/5/13 1/12/14 198.100.107.107 California, U.S Example parking of trendmicro-update org (Source: Dell SecureWorks) Endnotes [1] The Dell SecureWorks Counter Threat Unit(TM) (CTU) research team tracks threat groups by assigning them four-digit randomized numbers (3390 in this case), and compiles information from first-hand incident response observations and from external sources Visitors to the compromised website are redirected to a server under the threat group's control, where their system is compromised with the threat group's malware With this tactic, a threat group increases the likelihood of compromising systems that possess desired information  ### Response: .