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This has been advantageous to CrowdStrike incident responders in that, through investigating victim O365 environments, they could gain an accurate accounting of time, account and source IP address of adversary victimization of the O365 tenant. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In multiple engagements, this led CrowdStrike incident responders to identify that the malicious authentications into victim O365 tenants had originated from within the victim’s own network. | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Armed with this information, CrowdStrike investigators were able to identify from which systems in these internal networks the threat actor was making authentications to O365. | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
These authentications would typically occur from servers in the environment, leading to natural investigative questions: Why would a user authenticate into O365 from a domain controller or other infrastructure server? | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
What credentials were used as part of the session from which the O365 authentication occurred? | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This led our responders to identify the occurrence of “credential hopping,” where the threat actor leveraged different credentials for each step while moving laterally through the victim’s network. | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
While this particular technique is not necessarily unique to the StellarParticle campaign, it indicates a more advanced threat actor and may go unnoticed by a victim. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Below is an example of how a threat actor performs credential hopping: Gain access to the victim’s network by logging into a public-facing system via Secure Shell (SSH) using a local account <user sftp> acquired during previous credential theft activities. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Use port forwarding capabilities built into SSH on the public-facing system to establish a Remote Desktop Protocol (RDP) session to an internal server (Server 1) using a domain service account. | [
"T1021.001",
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
From Server 1, establish another RDP session to a different internal server (Server 2) using a domain administrator’s account. | [
"T1021.001",
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Log in to O365 as a user with privileged access to cloud resources. | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Example of “credential hopping” technique This technique could be hard to identify in environments where defenders have little visibility into identity usage. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In the example shown in Figure 1, the threat actor leveraged a service interactively, which should generate detections for defenders to investigate. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
However, the threat actor could have easily used a second domain administrator account or any other combination of accounts that would not be easily detected. | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
A solution such as CrowdStrike Falcon:registered: Identity Threat Detection would help identify these anomalous logons — and especially infrequent destinations for accounts. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
(Read how CrowdStrike incident responders leverage the module in investigations in this blog: Credentials, Authentications and Hygiene: Supercharging Incident Response with Falcon Identity Threat Detection.) | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
But how had the threat actor succeeded in authenticating into victim O365 tenants, when multifactor authentication (MFA) had been enabled for every O365 user account at each victim organization investigated by CrowdStrike? Cookie Theft to Bypass MFA Even though the victims required MFA to access cloud resources from al... | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The threat actor accomplished this by using administrative accounts to connect via SMB to targeted users, and then copy their Chrome profile directories as well as data protection API (DPAPI) data. | [
"T1078",
"T1570"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In Windows, Chrome cookies and saved passwords are encrypted using DPAPI. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The user-specific encryption keys for DPAPI are stored under C:\Users\<user>\AppData\Roaming\Microsoft\Protect\. To leverage these encryption keys, the threat actor must first decrypt them, either by using the user account’s Windows password, or, in Active Directory environments, by using a DPAPI domain backup key that... | [
"T1140"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Once the threat actor had a Chrome cookies file from a user that had already passed an MFA challenge recently (for example, a timeout was 24 hours), they decrypted the cookies file using the user’s DPAPI key. | [
"T1140"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The cookies were then added to a new session using a “Cookie Editor” Chrome extension that the threat actor installed on victim systems and removed after using. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Shellbags, Falcon Telemetry and RDP Bitmap Cache From a forensic standpoint, the use of the Cookie Editor Chrome extension would have been challenging to identify, due to the threat actor’s penchant for strict operational security. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This activity was identified via a NewScriptWritten event within Falcon when a JavaScript file was written to disk by a threat actor-initiated Chrome process. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This event captured the unique extension ID associated with the extension, thereby allowing CrowdStrike incident responders to validate via the Chrome Store that the JavaScript file was associated with the “Cookie Editor” plugin. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This extension permitted bypassing MFA requirements, as the cookies, replayed through the Cookie Editor extension, allowed the threat actor to hijack the already MFA-approved session of a targeted user. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Shellbags were also instrumental in identifying the cookie theft activity. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This artifact very clearly showed the threat actor accessing targeted users’ machines in sequence and browsing to the Chrome and DPAPI directories one after another. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Parsing Shellbags for an administrative account leveraged by the threat actor resulted in entries similar to the below. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Shellbag artifacts showing targeting of Chrome directories CrowdStrike identified forensic evidence that showed the entire attack path: browsing to a target user’s Chrome and DPAPI directories via administrative share, installing the Cookie Editor extension, and using Chrome to impersonate the targeted user in the vict... | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The decryption of the cookies is believed to have taken place offline after exfiltrating the data via the clipboard in the threat actor’s RDP session. | [
"T1021.001",
"T1140"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Representation of lateral movement to cookie theft to O365 authentication CrowdStrike identified a similar TTP where the threat actor connected via RDP to a user’s workstation with the workstation owner’s account (e.g., connecting via RDP to user1-pc using the account user1). | [
"T1021.001"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In cases where the user had only locked their screen and not signed out, the threat actor was able to take over the user’s Windows session, as the RDP session would connect to the existing session of the same user. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
By examining RDP Bitmap Cache files, CrowdStrike was able to demonstrate that the threat actor had opened Chrome and exported all of the user’s saved passwords as plaintext in a CSV file during these sessions. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Figure 4. RDP Bitmap Cache reconstruction showing exportation of Chrome passwords In addition, the threat actor visited sensitive websites that the user had access to, which in one instance allowed them to browse and download a victim’s customer list. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
After this, the threat actor navigated to the user’s Chrome history page and deleted the specific history items related to threat actor activity, leaving the rest of the user’s Chrome history intact. | [
"T1070.004"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
O365 Delegated Administrator Abuse CrowdStrike also identified a connection between StellarParticle-related campaigns and the abuse of Microsoft Cloud Solution Partners’ O365 tenants. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This threat actor abused access to accounts in the Cloud Solution Partner’s environment with legitimate delegated administrative privileges to then gain access to several customers’ O365 environments. | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
By analyzing Azure AD sign-ins, CrowdStrike was able to use known indicators of compromise (IOCs) to identify several threat actor logins to customer environments. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
These cross-tenant sign-ins were identified by looking for values in the resourceTenantId attribute that did not match the Cloud Solution Partner’s own Azure tenant ID. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
CrowdStrike also identified a limitation within Microsoft’s Delegated Administration capabilities for Microsoft Cloud Solution Partners. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
While a normal O365 administrator can be provided dozens of specific administrative roles to limit the privileges granted, this same degree of customization cannot be applied to Microsoft Cloud Solution Partners that use the delegated administrator functionality in O365. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
For Microsoft Cloud Solution Partners, there are only two substantial administrative options today when managing a customer’s environment, Admin agent or Helpdesk agent.2 | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The Helpdesk agent role provides very limited access that is equivalent to a password admin role, whereas the Admin agent role provides broad access more equivalent to global administrator. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This limitation is scheduled to be resolved in 2022 via Microsoft’s scheduled feature, Granular Delegated Admin Privileges (GDAP).3 User Access Logging (UAL) | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The Windows User Access Logging (UAL) database is an extremely powerful artifact that has played an instrumental role in the investigation of StellarParticle-linked cases. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In particular, UAL has helped our responders identify earlier malicious account usage that ultimately led to the identification of the aforementioned TrailBlazer implant and Linux version of the GoldMax variant. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The UAL database is available by default on Server editions of Windows starting with Server 2012. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This database stores historical information on user access to various services (or in Windows parlance, Roles) on the server for up to three years (three years minus one day) by default. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
UAL contains information on the type of service accessed, the user that accessed the service and the source IP address from which the access occurred. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
One of the most useful roles recorded by UAL is the File Server role, which includes SMB access, though other role types can also be very helpful. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
An overview of UAL, what information it contains and how it can be leveraged in forensic investigations can be found here. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In multiple StellarParticle-related cases, because the threat actor used the same set of accounts during their operations in the environment, CrowdStrike was able to identify previous malicious activity going back multiple years, based solely on UAL data. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Even though it’s only available on Server 2012 and up, UAL can still be used to trace evidence of threat actor activity on legacy systems as long as the activity on the legacy system involves some (deliberate or unintentional) access to a 2012+ system. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
For example, in addition to tracking SMB activity, UAL databases on Domain Controllers track Active Directory access. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This allowed CrowdStrike to demonstrate that a given user account was also authenticating to Active Directory from a given source IP address two years prior. | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Because the user account was known to have recently been abused by the threat actor, and the source IP of the system in question was not one that account would typically be active on, the investigation led to the source system and ultimately resulted in the timeline of malicious activity being pushed back by years, wit... | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
TrailBlazer and GoldMax Throughout StellarParticle-related investigations, CrowdStrike has identified two sophisticated malware families that were placed on victim systems in the mid-2019 timeframe: a Linux variant of GoldMax and a completely new family CrowdStrike refers to as TrailBlazer. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
TrailBlazer Attempted to blend in with a file name that matched the system name it resided on Configured for WMI persistence (generally uncommon in 2019) Used likely compromised infrastructure for C2 Masquerades its command-and-control (C2) traffic as legitimate Google Notifications HTTP requests TrailBlazer is a sophi... | [
"T1036.005",
"T1047",
"T1071.001"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The malware shares high-level functionality with other malware families. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In particular, the use of random identifier strings for C2 operations and result codes, and attempts to hide C2 communications in seemingly legitimate web traffic, were previously observed tactics, techniques and procedures (TTPs) in GoldMax and SUNBURST. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
TrailBlazer persists on a compromised host using WMI event subscriptions4 — a technique also used by SeaDuke — although this persistence mechanism is not exclusive to COZY BEAR.5 WMI event filter SELECT * FROM __ | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
InstanceModificationEvent | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
WITHIN 60 WHERE TargetInstance ISA 'Win32_PerfFormattedData_PerfOS_System' AND TargetInstance.SystemUpTime | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
>= 180 AND TargetInstance. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
SystemUpTime < 480 WMI Event consumer (CommandLineTemplate) C:\Program Files (x86)\Common Files\Adobe\<FILENAME>.exe Filter to consumer binding CommandLineEventConsumer. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Name="<GUID1>"|__EventFilter.Name="<GUID2>" Table 1. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
TrailBlazer WMI Persistence In the obfuscated example above, TrailBlazer (<FILENAME>.exe) would be executed when the system’s uptime was between 180 and 480 seconds. | [
"T1047"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
GoldMax (Linux variant) Attempted to blend in with a file name that matched the system name it resided on Configured for persistence via a crontab entry with a @reboot line Used likely compromised infrastructure for C2 GoldMax was first observed during post-exploitation activity in the campaign leveraging the SolarWind... | [
"T1036.005"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Previously identified samples of GoldMax were built for the Windows platform, with the earliest identified timestamp indicating a compilation in May 2020, but a recent CrowdStrike investigation discovered a GoldMax variant built for the Linux platform that the threat actor deployed in mid-2019. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This variant extends the backdoor’s known history and shows that the threat actor has used the malware in post-exploitation activity targeting other platforms than Windows. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The 2019 Linux variant of the GoldMax backdoor is almost identical in functionality and implementation to the previously identified May 2020 Windows variant. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The very few additions to the backdoor between 2019 and 2020 likely reflect its maturity and longstanding evasion of detections. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
It is likely GoldMax has been used as a long-term persistence backdoor during StellarParticle-related compromises, which would be consistent with the few changes made to the malware to modify existing functions or support additional functionality. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Persistence was established via a crontab entry for a non-root user. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
With the binary named to masquerade as a legitimate file on the system and placed in a hidden directory, a crontab entry was created with a @reboot line so the GoldMax binary would execute again upon system reboot. | [
"T1036.005",
"T1564.001"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Additionally, the threat actor used the nohup command to ignore any hangup signals, and the process will continue to run even if the terminal session was terminated. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Crontab entry for GoldMax persistence Enumeration Tools/Unique Directory Structure Throughout our StellarParticle investigations, CrowdStrike identified what appeared to be a VBScript-based Active Directory enumeration toolkit. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
While the script’s contents have not been recovered to date, CrowdStrike has observed identical artifacts across multiple StellarParticle engagements that suggest the same or similar tool was used. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In each instance the tool was used, Shellbags data indicated that directories with random names of a consistent length were navigated to by the same user that ran the tool. | [
"T1083"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
After two levels of randomly named directories, Shellbags proved the existence of subdirectories named after the FQDNs for the victims’ various domains. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In addition, the randomly named directories are typically created in a previously existing directory that’s one level off of the root of the C drive. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The randomly named directories have a consistent length where the first directory is six characters and the next directory is three characters. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
To date, the names of the directories have always been formed from lowercase alphanumeric characters. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
For example, Shellbags indicated that directories matching the naming patterns below were browsed to (where “XX” is a previously existing directory on the system): C:\XX\[a-z0-9]{6} C:\XX\[a-z0-9]{6}\[a-z0-9]{3} C:\XX\[a-z0-9]{6}\[a-z0-9]{3}\domain. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
FQDN C:\XX\[a-z0-9]{6}\[a-z0-9]{3}\domain-2.FQDN | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In each case, immediately prior to the creation of the directories referenced above, there was evidence of execution of a VBScript file by the same user that browsed to the directories. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This evidence typically came from a UserAssist entry for wscript.exe, as well as RecentApps entries for wscript.exe (that would also include the VBScript filename). | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In addition, the Jump List for wscript.exe contained evidence of the VBScript files. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The name of the VBScript files varied across engagements and was generally designed to look fairly innocuous and blend in. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Two examples are env.vbs and WinNet.vbs. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Due to the subdirectories that are named after the FQDNs for victim domains, CrowdStrike assesses with moderate confidence that the scripts represent an AD enumeration tool used by the adversary. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Internal Wiki Access Across multiple StellarParticle investigations, CrowdStrike identified unique reconnaissance activities performed by the threat actor: access of victims’ internal knowledge repositories.6 Wikis are commonly used across industries to facilitate knowledge sharing and as a source of reference for a va... | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
While operating in the victim’s internal network, the threat actor accessed sensitive information specific to the products and services that the victim organization provided. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
This information included items such as product/service architecture and design documents, vulnerabilities and step-by-step instructions to perform various tasks. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
Additionally, the threat actor viewed pages related to internal business operations such as development schedules and points of contact. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
In some instances these points of contact were subsequently targeted for further data collection. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The threat actor’s wiki access could be considered an extension of “Credential Hopping” described earlier. | [] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
The threat actor established RDP sessions to internal servers using privileged accounts and then accessed the wiki using a different set of credentials. | [
"T1021.001",
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
CrowdStrike observed the threat actor accessing the wiki as users who would be considered “non-privileged” from an Active Directory perspective but had access to sensitive data specific to the victim’s products or services. | [
"T1078"
] | Early Bird Catches the Wormhole Observations from the StellarParticle Campaign |
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