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As alluded to in our previous blog regarding the Cannon tool, the Sofacy group (AKA Fancy Bear, APT28, STRONTIUM, Pawn Storm, Sednit) has persistently attacked various government and private organizations around the world from mid-October 2018 through mid-November 2018. The majority of targets were NATO-aligned nation states, although several former USSR nation states were also targeted. The attacks primarily deployed variants of the Zebrocy tool, which we have previously analyzed. A smaller subset of the delivery documents delivered Cannon or a Zebrocy Delphi variant as reported by ESET. Since we began tracking the use of Zebrocy going back to mid-2015, we have observed a significant increase in frequency of deployment of this tool. Compared to other backdoor tools associated with the Sofacy group, the use of Zebrocy in attack campaigns is far more widespread.
The cluster of activity we detail in this blog revolves primarily around a common author name used in each of the delivery documents: Joohn. Our initial sample of interest was the delivery document using the crash list(Lion Air Boeing 737).docx filename, which delivered the Zebrocy tool. By leveraging our AutoFocus threat intelligence platform in conjunction with data collected from VirusTotal, we were able to pivot from artifacts discovered in the metadata and behaviors to discover the Cannon tool, as well as a number of additional delivery documents, payloads, and targets. The attack vector for all of these attacks appears to be via spear-phishing, using email accounts registered to legitimate email providers instead of spoofed email addresses or previously compromised accounts. The account names visually look similar to legitimate government organization names or other trusted third-party entities. The delivery documents were functionally all the similar, using the remote template function in Microsoft Word to retrieve a malicious macro from the first stage C2 and ultimately loading and executing an initial payload. The majority of delivery documents contain a generic lure image requesting the victim enable macros with no additional content, the adversaries seemingly relying solely on lure filenames to entice victims to launch the malicious document.
In all, we intercepted nine weaponized documents spanning from October 17, 2018 through November 15, 2018 all sharing the same Joohn author name and delivering variants of either Zebrocy or Cannon. The target radius of our dataset spans four continents, covering government agencies at the federal level all the way to local government agencies. We also conducted timeline analysis using the collected data which allowed us to discover how the Sofacy group timed their attacks in the Dear Joohn campaign and also how they may have crafted their attacks using automated tools.
Beginning on October 17, 2018, we collected a total of nine delivery documents sent to a multitude of organizations around the world. The targets included a foreign affairs organization in North America, foreign affairs organizations in Europe, as well as government entities in former USSR states. We also discovered evidence of possible targeting of local law enforcement agencies around the world, covering North America, Australia, and Europe. Our telemetry also showed possible targeting of NGOs, marketing firms, as well as organizations in the medical industry. The attack vector of these attacks was all via spear-phishing, using email accounts registered to the free email provider Seznam, a popular web services provider located in the Czech Republic. An example can be seen in Figure 1.
Figure 1 Example spear-phishing email delivered in Dear Joohn attacks
In this campaign, the Sofacy group appears to have relied heavily on filenames to lure victims into launching the weaponized documents. Filenames ranged from topics alluding to Brexit, the Lion Air crash, and recent rocket attacks in Israel. The full list of filenames we were able to collect can be seen in Table 1. Although the filenames appeared to be highly targeted and pertinent to the victims, the actual lure content of the documents were far more generic as seen in Figure 2.
Figure 2 Generic lure image
In November 2018, the adversary shifted tactics and began implementing non-generic lure content for their weaponized documents. We collected three samples heavily targeting NATO-aligned nation states at this time, using three different lures as seen in Figure 3.
Figure 3 Targeted lure content
In one of the documents, the victim is presented with what appears to be an obfuscated document with the NATO EOD seal and text alluding to the targeted nation state. Unpacking the document revealed that the unobfuscated image was a screenshot of a cover page regarding a NATO workshop in the targeted nation state. The other two documents had very similar lures to each other, presenting garbled text to the target with instructions for the victim on how to properly view the document. Interestingly, one of them contained instructions in Russian, which may indicate the intended target was a Russian speaking nation-state.
Each of these weaponized documents used the same tactic for their attacks. Upon opening the document, it leveraged the ability of Microsoft Word to retrieve a remote template to then load a malicious macro document as seen in Figure 4.
Figure 4 Microsoft Word attempting to download the remote template
If the C2 server is active at the time the document is opened, it will successfully retrieve the malicious macro and load it in the same Microsoft Word session. The victim will then see a prompt to Enable Content as with any malicious macro document as seen in Figure 5. If the C2 server is not active at this time, the download will fail and the victim will not receive a prompt to Enable Content as no macro is downloaded.
Figure 5 Remote template document requesting the user to click "Enable Content" to run macro
The delivery documents used in the October and November waves shared a large number of similarities, as seen in Table 1, which allowed us to cluster the activity together. Most notably, the author name Joohn was used repeatedly in each delivery document. There was a slight deviation in the November grouping, where the three samples we collected still used the Joohn author name for the last modified field but reverted to a default USER/user author name for the creator field.
|Hash||Filename||Created By||Last Modified By||Remote Template Location||Remote Template Hash|
|40318f3593..||DN_325_170428_DEA Basic Narcotics Investigation Course invitation.docx||Joohn||Joohn||145.249.105[.]165||2da5a388b8..|
|2cfc4b3686..||crash list(Lion Air Boeing 737).docx||Joohn||Joohn||188.241.58[.]170||f1e2bceae8..|
|34bdb5b364..||Rocket attacks on Israel.docx||user||Joohn||109.248.148[.]42||ed8f52cdfc..|
DIP 89 OIC Condemns 14 Nov Attacks.docx
Table 1 Delivery documents seen in the Dear Joohn attack campaign
The remote template documents retrieved by the delivery documents in Table 1 also shared a common author name, using the string xxx.Table 2 shows the remote templates downloaded by delivery documents in this attack campaign. In the tables and text of this report, we are referring to samples by a shortened version of their SHA256 hash to improve readability. The full hashes and metadata are available in CSV format here.
|Created||Last Modified||Hosted on IP|
|f1e2bceae8..||office.dotm||xxx||10/31/18 10:52||10/31/18 10:52||188.241.58[.]170|
|86bb3b00bc..||Note_template.dotm||xxx||10/17/18 05:35||10/17/18 05:35||185.203.118[.]198|
|2da5a388b8..||release.dotm||xxx||10/25/18 07:06||10/25/18 07:06||145.249.105[.]165|
|0d7b945b9c..||message_template.dotm||xxx||10/23/18 13:55||10/23/18 13:55||145.249.105[.]165|
|fc69fb278e..||documents.dotm||xxx||11/01/18 05:00||11/01/18 05:06||188.241.58[.]170|
|ed8f52cdfc..||templates.dotm||xxx||11/13/18 10:52||11/13/18 10:52||109.248.148[.]42|
|b9f3af84a6..||attachedTemplate.dotm||xxx||11/15/18 05:35||11/15/18 05:35||109.248.148[.]42|
Table 2 Remote templates downloaded by Dear Joohn delivery documents
As seen in Table 1, the delivery documents accessed their respective remote templates from four C2 servers at the following IP addresses:
These initial C2 IP addresses not only hosted the remote templates that subsequently load the first-stage Zebrocy or Cannon payloads, but the IP addresses also hosted the C2 server for the first-stage payloads themselves. All C2s used in the Dear Joohn campaign were IP-based and examining the infrastructure did not provide significant overlap or relationships with previous Zebrocy or Sofacy infrastructure. A visual representation of the Dear Joohn campaign can be seen in Figure 6.
Figure 6 Relational diagram of artifacts
We created a timeline of the activity based off the data we collected, and found that the attack dates were tightly clustered into two waves in mid- to late-October and in mid-November as we see in Figure 7 using the timestamps from Table 3.
|Filename||Created On||Last Modified||First Seen||Total Time (In Days)|
|9/11/18 04:22||10/13/18 08:21||10/18/18 07:38||37.1|
|DN_325_170428_DEA...invitation.docx||9/11/18 04:22||10/13/18 08:21||10/25/18 08:15||44.12|
|crash list(Lion Air Boeing 737).docx
|9/11/18 04:22||10/13/18 08:21||11/01/18 06:50||51.1|
|Заявление.docx||9/11/18 04:22||10/13/18 08:21||11/01/18 11:41||51.3|
|1500029.docx||10/18/18 06:59||10/18/18 07:00||10/18/18 08:47||0.4|
|2018_10_13_17_15_21.docx||10/18/18 06:59||10/18/18 07:00||10/24/18 07:38||6.2|
|Rocket attacks on Israel.docx||11/13/18 12:17||11/13/18 10:46||11/14/18 05:14||0.7|
DIP 89 OIC Condemns 14 Nov Attacks.docx
|11/14/18 14:17||11/15/18 04:50||11/15/18 06:28||0.8|
|201811131257.docx||11/14/18 14:33||11/15/18 04:50||11/15/18 12:31||0.9|
Table 3 Timestamps of delivery documents (all times in UTC)
Figure 7 Dear Joohn timeline
Based off the timestamps we have, four delivery documents were initially created on September 11, 2018 04:22 UTC. These four were then all modified on the same date and time on October 13, 2018 08:21. Having three different C2 locations embedded inside these delivery documents while maintaining the exact same timestamping may indicate the use of an automated tool. Using a command line based penetration testing toolkit such as Phishery could allow for simple scripting to generate multiple documents all at the same time with different inputs. From there, there was an average of a two-week gap until these documents were first seen in the wild. In total, these four documents had an average of roughly 46 days from initial creation to attack. Based on the modular nature of the Dear Joohn campaign attacks, the lengthy amount of time from initial creation to attack may suggest the campaign was not yet ready for deployment due to additional development required for the remote templates, payloads, or infrastructure. Another possible scenario is that the adversary may have had a certain timeframe they desired to execute the attack, and from the timeline it is clear there were two distinct targeting time frames, one from mid to late October 2018 and the other in mid-November 2018. As the campaign progressed, the operational tempo of the Dear Joohn campaign increased, with the total time from document creation to first seen dropping down to an average of roughly two days.
When comparing the provided timestamps of the delivery documents to the timestamps for the remote template documents from Table 2, we find that the time to attack is directly correlated to the last time the templates are modified. On average, there was a 13.8 hour gap between when the template document was last touched by the operator and when the delivery document is first observed in the wild. This leads us to believe that the generation of the delivery documents were indeed part of a staging effort, first with the initial creation of the document, modification to it to communicate with a C2, then generating a remote template document just prior to launching the actual attack.
Analysis using timestamps is not always conclusive however. One of the documents we examined with the filename Rocket attacks on Israel.docx (SHA256: 34bdb5b364..) contained inconsistent creation and last modified timestamps, with the last modified timestamp occurring before the creation timestamp. A possible explanation for this is that the document was copied to another system with an incorrectly set system time, then saved with the incorrect time. This document was also the first of the mid-November cluster which used the user/USER author name instead of Joohn, further supporting the scenario of the document being copied between systems.
The delivery documents in this attack campaign loaded remote templates whose macros installed a variety of first-stage payloads. With the notable exception of the Cannon tool, the first-stage tools are all variants of the Zebrocy Trojan. The Zebrocy variants delivered in this campaign were written in several different languages, including Delphi, C# and VB.NET. Information on the first-stage payloads delivered in this attack are listed in Table 4.
Table 4 Payloads delivered in related attacks
The Delphi variant of Zebrocy delivered in this attack campaign are very similar to the Delphi downloader discussed in our previous Zebrocy research published in June 2018. While this Delphi variant was known, the C# and VB.NET variants delivered in this attack campaign were previously unknown. An interesting note on these payloads is that all the Delphi payloads delivered in this campaign were packed with UPX, while none of the other payloads were packed. While we can only speculate on the specific reason, it is likely Sofacy packed only the Delphi variants in an attempt to increase evasion as the Delphi variant of Zebrocy is known and has been widely analyzed.
By collecting and analyzing additional Cannon samples, we believe we have also found a Cannon variant written in Delphi. We have seen Sofacy using multiple languages to create variants of the Zebrocy Trojan, so it seems fitting that the group would create additional variants of Cannon in multiple programming languages as well.
Since our initial blog that introduced the Cannon tool, we were able to collect more samples of Cannon to get a better understanding of its origins. It appears that the first known sample of Cannon was created on April 18, 2018 and since then there has been at least seven additional samples. Table 5 shows the known Cannon samples, their compilation time and the email accounts used for its C2 communications.
|SHA256||Compiled||C2 account||POP3S Account||SMTPS Accounts|
Table 5 Gathered C# Cannon samples
As mentioned in our initial blog, the actor controlled email address acting as the C2 was sahro.bella7[at]post.cz, but all previous samples of Cannon used sym777.g[at]post.cz. Also, all previous samples of Cannon used an account name of kae.mezhnosh to receive emails from the actor, while using the accounts vebek.morozh30, g0r7tsa45s and marvel.polezha to send emails to the actor.
As we reported in our previous analysis of Cannon, the tool logs into an email account using POP3S and checks for emails with a specific filename that it will save to the system and execute. The initial sample we analyzed looked for an attachment with a filename of auddevc.txt, but other Cannon samples have looked for the following filenames instead:
While searching for additional Cannon samples, we discovered another tool that used emails for its C2 communications. The initial overlap was based on the filename wmssl.exe, which was seen as an executable name that Cannon would move the wmssl.txt attachment to install and execute a secondary payload. Initial analysis indicated this may have been a tenuous connection; however, after we gathered additional samples of Delphi Cannon, we discovered additional relationships. Table 6 shows Delphi Cannon samples we gathered, including the sample 215f7c08c2.. that is very similar to the Trojan discussed in ESET’s research.
|SHA256||Compiled||C2 email||POP3S Account||SMTPS Accounts|
Table 6 Gathered Delphi Cannon Samples
The compilation times in Table 6 suggests that the Delphi variant of Cannon predates the originally reported version, as the first known Delphi sample was compiled in January 2018 and the first known Cannon sample was compiled in April 2018. The Delphi variant of Cannon does not use legitimate web-based email services for its C2 communications, instead opting to use email accounts at an actor owned domain, ambcomission[.]com. This actor controlled domain links to a larger Sofacy infrastructure as reported by ThreatConnect. Even though Delphi Cannon uses POP3S and SMTPS for its C2 communications like Cannon, it is arguably easier to defend against as it uses an actor owned domain that defenders can easily block and not a legitimate email provider such as Seznam.
The oldest known sample of the Delphi variant (SHA256: 5a02d4e5f6…) provided us a much stronger linkage between this Delphi Cannon and Cannon, as this sample collects system information and sends it to the C2 email address, which includes the path of the running process appended to the string Running place. The screenshot in Figure 8 of the inf method within a Cannon sample (SHA256: 4405cfbf28...) shows the information gathered that is exfiltrated to the C2 via email, specifically with RunningPlace and LogicalDrives header strings:
Figure 8 inf method used by Cannon
When comparing the two Cannon variants, we found a method within a Delphi Cannon sample (SHA256: 5a02d4e5f6...) showing the use of Running place and Logical_Drivers as header strings to the system information it is collecting and sending to the C2 via email. While not an exact match, Figure 9 shows these similar header strings and strengthens our hypothesis that the two variants are indeed related:
Figure 9 Similarities of Delphi Cannon and Cannon
As seen in Table 6, one of the Delphi Cannon samples (SHA256: cac630c11c..) does not have any associated email addresses, as the sample does not seem to have any C2 functionality. Instead, this sample reads “tasks” from a file named ta.bin that another unknown tool then must write to and handle C2 functionality. It is also interesting that this specific sample has the same resource name (L30) that contains the same encrypted email addresses as the other samples in Table 6 using heatlth500@ambcomission[.]com as a C2 email (such as ecc5805898..) but does not contain any code to access the resource or decrypt its contents.
VB.NET Zebrocy Variant
The VB.NET variant (SHA256: e5aece694d..) is very similar to other known Zebrocy variants. It includes the storage volume serial number within the URL it uses as its C2 beacon, which it obtains using the Scripting.FileSystemObject object to call GetDriveName from the path stored in Environment.SpecialFolder.LocalApplicationData. It then uses the storage volume obtained from the GetDriveName function and calls GetDrive to get the SerialNumber of the storage device. The VB.NET variant then gathers system information and running processes like other Zebrocy variants by running the following commands:
systeminfo & tasklist
The URL used to send the system information, running processes and a screenshot to the C2 server is:
The VB.NET variant of Zebrocy uses an HTTP POST request to the URL above to transmit the gathered data, of which is included within the HTTP POST data that is structured as follows (notice the spaces before and after ampersand “&”):
data=[system information and running processes] & arg=[screenshot in BMP format]
C# Zebrocy Variant
The C# variant of Zebrocy is similar to other variants in functionality, but also has several unique attributes that are worth discussing. Like other Zebrocy tools, the C# variant gathers the storage volume serial number to use in outbound beacons to the C2 server. In this particular variant, the tool uses the Windows API function GetVolumeInformation to get the serial number of the C: drive. This variant of Zebrocy also takes a screenshot that it will transmit to the C2 server in JPEG format.
The most notable change to this variant of Zebrocy, other than the programming language used, is the way the tool gathers the system information and running processes. Instead of using systeminfo and tasklist commands, the C# variant of Zebrocy uses WMI queries to gather this information. The tool runs the following list of WMI queries:
- wmic logicaldisk get Caption, Description,VolumeSerialNumber,Size,FreeSpace
- wmic diskdrive get Model, SerialNumber
- wmic computersystem get Manufacturer, Model, Name, SystemTypec
- wmic os get Caption, OSArchitecture, OSLanguage,SystemDrive,MUILanguages
- wmic process get Caption,ExecutablePath
The URL used to send the system information, running processes and a screenshot to the C2 server is:
The C# variant of Zebrocy uses an HTTP POST request to the URL above to transmit the gathered data, of which is included within the HTTP POST data that is structured as follows:
spp=[system information from WMI queries] &spvg=[screenshot in JPEG format]
The Sofacy group continues their attacks on organizations across the globe using similar tactics and techniques. We observed them carrying out attacks via spear-phishing emails in late October through November, often leveraging current events within filenames to entice recipients to open the malicious attachments. The group clearly shows a preference for using a simple downloader like Zebrocy as first-stage payloads in these attacks. The group continues to develop new variations of Zebrocy by adding a VB.NET and C# version, and it appears that they also have used different variants of the Cannon tool in past attack campaigns.
Palo Alto Networks customers are protected by attacks discussed in this blog by:
- All delivery documents and payloads discussed are detected with malicious verdicts in WildFire
- Traps blocks the macro laden documents as Suspicious macro detected
- C2 URLs have been classified as Command and Control
- AutoFocus customers may learn more via the Zebrocy and Cannon tags
Indicators of Compromise
Remote Template Hashes
Remote Template URLs
Zebrocy C2 URLs
Cannon Related Emails
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