CrowdStrike Falcon Platform Detects and Prevents Active Intrusion Campaign Targeting 3CXDesktopApp Customers

Note: Content from this post first appeared in r/CrowdStrike

3/31 UPDATE After review and reverse engineering by the CrowdStrike Intelligence team, the signed MSI (aa124a4b4df12b34e74ee7f6c683b2ebec4ce9a8edcf9be345823b4fdcf5d868) is malicious.

The MSI will drop three files, with the primary fulcrum being the compromised binary ffmpeg.dll (7986bbaee8940da11ce089383521ab420c443ab7b15ed42aed91fd31ce833896).

Once active, the HTTPS beacon structure and encryption key match those observed by CrowdStrike in a March 7, 2023 campaign attributed with high confidence to DPRK-nexus threat actor LABYRINTH CHOLLIMA.

All Falcon customers can view our actor profile on LABYRINTH CHOLLIMA (US-1 | US-2 | EU-1 | US-GOV-1)

CrowdStrike Intelligence Premium subscribers can view the following reports for full technical details:

• CSA-230387: LABYRINTH CHOLLIMA Uses TxRLoader and Vulnerable Drivers to Target Financial and Energy Sectors (US-1 | US-2 | EU-1 | US-GOV-1)
• CSA-230489: LABYRINTH CHOLLIMA Suspected of Conducting Supply Chain Attack with 3CX Application (US-1 | US-2 | U-1 | US-GOV-1)
• CSA-230494: ArcfeedLoader Malware Used in Supply Chain Attack Leveraging Trojanized 3CX Installers Confirms Attribution to LABYRINTH CHOLLIMA (US-1 | US-2 | U-1 | US-GOV-1)

CrowdStrike recommends removing the 3CX software from endpoints until advised by the vendor that future installers and builds are safe.

Falcon Spotlight customers can search for CVE-2023-3CX to identify vulnerable versions of 3CX software. Spotlight will automatically highlight this vulnerability in your vulnerability feed.

Original Post

On March 29, 2023, CrowdStrike observed unexpected malicious activity emanating from a legitimate, signed binary, 3CXDesktopApp — a softphone application from 3CX. The malicious activity includes beaconing to actor-controlled infrastructure, deployment of second-stage payloads, and, in a small number of cases, hands-on-keyboard activity.

The CrowdStrike Falcon^® platform has behavioral preventions and atomic indicator detections targeting the abuse of 3CXDesktopApp. In addition, CrowdStrike^® Falcon OverWatch™ helps customers stay vigilant against hands-on-keyboard activity.

CrowdStrike customers can log into the customer support portal and follow the latest updates in Trending Threats & Vulnerabilities: Intrusion Campaign Targeting 3CX Customers

The 3CXDesktopApp is available for Windows, macOS, Linux and mobile. At this time, activity has been observed on both Windows and macOS.

CrowdStrike Intelligence has assessed there is suspected nation-state involvement by the threat actor LABYRINTH CHOLLIMA. CrowdStrike Intelligence customers received an alert this morning on this active intrusion.

Get fast and easy protection with built-in threat intelligence — request a free trial of CrowdStrike Falcon^® Pro today.

CrowdStrike Falcon Detection and Protection

Watch how the CrowdStrike Falcon platform detects and prevents an active intrusion campaign targeting 3CXDesktopApp users.

The CrowdStrike Falcon platform protects customers from this attack and has coverage utilizing behavior-based indicators of attack (IOAs) and indicators of compromise (IOCs) based detections targeting malicious behaviors associated with 3CX on both macOS and Windows.

Customers should ensure that prevention policies are properly configured with Suspicious Processes enabled.

Figure 1. CrowdStrike’s indicator of attack (IOA) identifies and blocks the malicious behavior in macOS (click to enlarge)

Figure 2. CrowdStrike’s indicator of attack (IOA) identifies and blocks the malicious behavior in Windows (click to enlarge)

Hunting in the CrowdStrike Falcon Platform

Falcon Discover CrowdStrike Falcon^® Discover customers can use the following link: US-1 | US-2 | EU-1 | US-GOV-1 to look for the presence of 3CXDesktopApp in their environment.

Falcon Insight customers can assess if the 3CXDesktopApp is running in their environment with the following query:

Event Search — Application Search

event_simpleName IN (PeVersionInfo, ProcessRollup2) FileName IN ("3CXDesktopApp.exe", "3CX Desktop App")
| stats dc(aid) as endpointCount by event_platform, FileName, SHA256HashData

Falcon Long Term Repository (LTR) powered by Falcon LogScale — Application Search

#event_simpleName=/^(PeVersionInfo|ProcessRollup2)$/ AND (event_platform=Win ImageFileName=/\\3CXDesktopApp\.exe$/i) OR (event_platform=Mac ImageFileName=/\/3CX\sDesktop\sApp/i)
| ImageFileName = /.+(\\|\/)(?<FileName>.+)$/i
| groupBy(, function=count(aid, distinct=true, as=endpointCount))

Atomic Indicators

The following domains have been observed beaconing, which should be considered an indication of malicious intent.

akamaicontainer<.>com
akamaitechcloudservices<.>com
azuredeploystore<.>com
azureonlinecloud<.>com
azureonlinestorage<.>com
dunamistrd<.>com
glcloudservice<.>com
journalide<.>org
msedgepackageinfo<.>com
msstorageazure<.>com
msstorageboxes<.>com
officeaddons<.>com
officestoragebox<.>com
pbxcloudeservices<.>com
pbxphonenetwork<.>com
pbxsources<.>com
qwepoi123098<.>com
sbmsa<.>wiki
sourceslabs<.>com
visualstudiofactory<.>com
zacharryblogs<.>com

CrowdStrike Falcon^® Insight customers, regardless of retention period, can search for the presence of these domains in their environment spanning back one year using Indicator Graph: US-1 | US-2 | EU-1 | US-GOV-1. Event Search — Domain Search

event_simpleName=DnsRequest DomainName IN (akamaicontainer.com, akamaitechcloudservices.com, azuredeploystore.com, azureonlinecloud.com, azureonlinestorage.com, dunamistrd.com, glcloudservice.com, journalide.org, msedgepackageinfo.com, msstorageazure.com, msstorageboxes.com, officeaddons.com, officestoragebox.com, pbxcloudeservices.com, pbxphonenetwork.com, pbxsources.com, qwepoi123098.com, sbmsa.wiki, sourceslabs.com, visualstudiofactory.com, zacharryblogs.com)
| stats dc(aid) as endpointCount, earliest(ContextTimeStamp_decimal) as firstSeen, latest(ContextTimeStamp_decimal) as lastSeen by DomainName
| convert ctime(firstSeen) ctime(lastSeen)

Falcon LTR — Domain Search

#event_simpleName=DnsRequest
| in(DomainName, values=)
| groupBy(, function=())
| firstSeen := firstSeen * 1000 | formatTime(format="%F %T.%L", field=firstSeen, as="firstSeen")
| lastSeen := lastSeen * 1000 | formatTime(format="%F %T.%L", field=lastSeen, as="lastSeen")
| sort(endpointCount, order=desc)

File Details

Recommendations

The current recommendation for all CrowdStrike customers is:

1. Locate the presence of 3CXDesktopApp software in your environment by using the queries outlined above.
2. Ensure Falcon is deployed to applicable systems.
3. Ensure “Suspicious Processes” is enabled in applicable Prevention Policies.
4. Hunt for historical presence of atomic indicators in third-party tooling (if available).

CrowdStrike Intelligence Confidence Assessment

High Confidence: Judgments are based on high-quality information from multiple sources. High confidence in the quality and quantity of source information supporting a judgment does not imply that that assessment is an absolute certainty or fact. The judgment still has a marginal probability of being inaccurate.

Moderate Confidence: Judgments are based on information that is credibly sourced and plausible, but not of sufficient quantity or corroborated sufficiently to warrant a higher level of confidence. This level of confidence is used to express that judgments carry an increased probability of being incorrect until more information is available or corroborated.

Low Confidence: Judgments are made where the credibility of the source is uncertain, the information is too fragmented or poorly corroborated enough to make solid analytic inferences, or the reliability of the source is untested. Further information is needed for corroboration of the information or to fill known intelligence gaps.

Additional Resources

• Request a free CrowdStrike Intelligence threat briefing and learn how to stop adversaries targeting your organization.
• The industry-leading CrowdStrike Falcon platform sets the new standard in cybersecurity. Watch this demo to see the Falcon platform in action.
• Experience how the industry-leading CrowdStrike Falcon platform protects against modern threats. Start your 15-day free trial today.
• Find more information on this situation on our Trending Threats & Vulnerabilities: Intrusion Campaign Targeting 3CX Customers tracking page.