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Entry via Sentry: Analyzing the Exploitation of a Critical Vulnerability in Ivanti Sentry

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20

Dec 2023

20

Dec 2023

In late August 2023, Darktrace observed malicious actors exploiting vulnerabilities on Ivanti Sentry servers within customer networks. Following these successful exploits, a variety of cryptomining and reconnaissance tools were delivered. In this blog, we will provide details of these chains of activity, along with details of Darktrace/Network’s coverage of the steps involved in them.

In an increasingly interconnected digital landscape, the prevalence of critical vulnerabilities in internet-facing systems stands as an open invitation to malicious actors. These vulnerabilities serve as a near limitless resource, granting attackers a continually array of entry points into targeted networks.

In the final week of August 2023, Darktrace observed malicious actors validating exploits for one such critical vulnerability, likely the critical RCE vulnerability, CVE-2023-38035, on Ivanti Sentry servers within multiple customer networks. Shortly after these successful tests were carried out, malicious actors were seen delivering crypto-mining and reconnaissance tools onto vulnerable Ivanti Sentry servers.

Fortunately, Darktrace DETECT™ was able to identify this post-exploitation activity on the compromised servers at the earliest possible stage, allowing the customer security teams to take action against affected devices. In environments where Darktrace RESPOND™ was enabled in autonomous response mode, Darktrace was further able inhibit the identified post-exploitation activity and stop malicious actors from progressing towards their end goals.

Exploitation of Vulnerabilities in Ivanti Products

The software provider, Ivanti, offers a variety of widely used endpoint management, service management, and security solutions. In July and August 2023, the Norwegian cybersecurity company, Mnemonic, disclosed three vulnerabilities in Ivanti products [1]/[2]/[3]; two in Ivanti's endpoint management solution, Ivanti Endpoint Manager Mobile (EPMM) (formerly called 'MobileIron Core'), and one in Ivanti’s security gateway solution, Ivanti Sentry (formerly called 'MobileIron Sentry'):

CVE-2023-35078

CVSS Score: 10.0
Affected Product: Ivanti EPMM
Details from Ivanti: [4]/[5]/[6]
Vulnerability type: Authentication bypass

CVE-2023-35081

CVSS Score: 7.2
Affected Product: Ivanti EPMM
Details from Ivanti: [7]/[8]/[9]
Vulnerability type: Directory traversal

CVE-2023-38035

CVSS Score:
Affected Product: Ivanti Sentry
Details from Ivanti: [10]/[11]/[12]
Vulnerability type: Authentication bypass

At the beginning of August 2023, the Cybersecurity and Infrastructure Security Agency (CISA) and the Norwegian National Cyber Security Centre (NCSC-NO) provided details of advanced persistent threat (APT) activity targeting EPMM systems within Norwegian private sector and government networks via exploitation of CVE-2023-35078 combined with suspected exploitation of CVE-2023-35081.

In an article published in August 2023 [12], Ivanti disclosed that a very limited number of their customers had been subjected to exploitation of the Ivanti Sentry vulnerability, CVE-2023-38035, and on the August 22, 2023, CISA added the Ivanti Sentry vulnerability, CVE-2023-38035 to its ‘Known Exploited Vulnerabilities Catalogue’. CVE-2023-38035 is a critical authentication bypass vulnerability affecting the System Manager Portal of Ivanti Sentry systems. The System Manager Portal, which is accessible by default on port 8433, is used for administration of the Ivanti Sentry system. Through exploitation of CVE-2023-38035, an unauthenticated actor with access to the System Manager Portal can achieve Remote Code Execution (RCE) on the underlying Ivanti Sentry system.

Observed Exploitation of CVE-2023-38035

On August 24, Darktrace observed Ivanti Sentry servers within several customer networks receiving successful SSL connections over port 8433 from the external endpoint, 34.77.65[.]112. The usage of port 8433 indicates that the System Manager Portal was accessed over the connections. Immediately after receiving these successful connections, Ivanti Sentry servers made GET requests over port 4444 to 34.77.65[.]112. The unusual string ‘Wget/1.14 (linux-gnu)’ appeared in the User-Agent headers of these requests, indicating that the command-line utility, wget, was abused to initiate the requests.

Figure 1: Event Log data for an Ivanti Sentry system showing the device breaching a range of DETECT models after contacting 34.77.65[.]112.The suspicious behavior highlighted by DETECT was subsequently investigated by Darktrace’s Cyber AI Analyst™, which was able to weave together these separate behaviors into single incidents representing the whole attack chain.

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Figure 2: AI Analyst Incident representing a chain of suspicious activities from an Ivanti Sentry server.

In cases where Darktrace RESPOND was enabled in autonomous response mode, RESPOND was able to automatically enforce the Ivanti Sentry server’s normal pattern of life, thus blocking further exploit testing.

Figure 3: Event Log for an Ivanti Sentry server showing the device receiving a RESPOND action immediately after trying to 34.77.65[.]112.

The GET requests to 34.77.65[.]112 were responded to with the following HTML document:

Figure 4: Snapshot of the HTML document returned by 34.77.65[.]112.

None of the links within this HTML document were functional. Furthermore, the devices’ downloads of these HTML documents do not appear to have elicited further malicious activities. These facts suggest that the observed 34.77.65[.]112 activities were representative of a malicious actor validating exploits (likely for CVE-2023-38035) on Ivanti Sentry systems.

Over the next 24 hours, these Ivanti Sentry systems received successful SSL connections over port 8433 from a variety of suspicious external endpoints, such as 122.161.66[.]161. These connections resulted in Ivanti Sentry systems making HTTP GET requests to subdomains of ‘oast[.]site’ and ‘oast[.]live’. Strings containing ‘curl’ appeared in the User-Agent headers of these requests, indicating that the command-line utility, cURL, was abused to initiate the requests.

These ‘oast[.]site’ and ‘oast[.]live’ domains are used by the out-of-band application security testing (OAST) service, Interactsh. Malicious actors are known to abuse this service to carry out out-of-band (OOB) exploit testing. It, therefore, seems likely that these activities were also representative of a malicious actor validating exploits for CVE-2023-38035 on Ivanti Sentry systems.

Figure 5: Event Log for Ivanti Sentry system showing the device contacting an 'oast[.]site' endpoint after receiving connections from the suspicious, external endpoint 122.161.66[.]161.

The actors seen validating exploits for CVE-2023-38035 may have been conducting such activities in preparation for their own subsequent malicious activities. However, given the variety of attack chains which ensued from these exploit validation activities, it is also possible that they were carried out by Initial Access Brokers (IABs) The activities which ensued from exploit validation activities identified by Darktrace fell into two categories: internal network reconnaissance and cryptocurrency mining.

Reconnaissance Activities

In one of the reconnaissance cases, immediately after receiving successful SSL connections over port 8443 from the external endpoints 190.2.131[.]204 and 45.159.248[.]179, an Ivanti Sentry system was seen making a long SSL connection over port 443 to 23.92.29[.]148, and making wget GET requests over port 4444 with the Target URIs '/ncat' and ‘/TxPortMap’ to the external endpoints, 45.86.162[.]147 and 195.123.240[.]183.

Figure 6: Event Log data for an Ivanti Sentry system showing the device making connections to the external endpoints, 45.86.162[.]147, 23.92.29[.]148, and 195.123.240[.]183, immediately after receiving connections from rare external endpoints.

The Ivanti Sentry system then went on to scan for open SMB ports on systems within the internal network. This activity likely resulted from an attacker dropping a port scanning utility on the vulnerable Ivanti Sentry system.

Figure 7: Event Log data for an Ivanti Sentry server showing the device breaching several DETECT models after downloading a port scanning tool from 195.123.240[.]183.

In another reconnaissance case, Darktrace observed multiple wget HTTP requests with Target URIs such as ‘/awp.tar.gz’ and ‘/resp.tar.gz’ to a suspicious, external server (78.128.113[.]130). Shortly after making these requests, the Ivanti Sentry system started to scan for open SMB ports and to respond to LLMNR queries from other internal devices. These behaviors indicate that the server may have installed an LLMNR poisoning tool, such as Responder. The Ivanti Sentry server also went on to conduct further information-gathering activities, such as LDAP reconnaissance, HTTP-based vulnerability scanning, HTTP-based password searching, and RDP port scanning.

Figure 8: Event Log data for an Ivanti Sentry system showing the device making connections to 78.128.113[.]130, scanning for an open SMB port on internal endpoints, and responding to LLMNR queries from internal endpoints.

In cases where Darktrace RESPOND was active, reconnaissance activities resulted in RESPOND enforcing the Ivanti Sentry server’s pattern of life.

Figure 9: Event Log data for an Ivanti Sentry system receiving a RESPOND action as a result of its SMB port scanning activity.

Figure 10: Event Log data for an Ivanti Sentry system receiving a RESPOND action as a result of its LDAP reconnaissance activity.

Crypto-Mining Activities

In one of the cryptomining cases, Darktrace detected an Ivanti Sentry server making SSL connections to aelix[.]xyz and mining pool endpoints after receiving successful SSL connections over port 8443 from the external endpoint, 140.228.24[.]160.

Figure 11: Event Log data for an Ivanti Sentry system showing the device contacting aelix[.]xyz and mining pool endpoints immediately after receiving connections from the external endpoint, 140.228.24[.]160.

In a cryptomining case on another customer’s network, an Ivanti Sentry server was seen making GET requests indicative of Kinsing malware infection. These requests included wget GET requests to 185.122.204[.]197 with the Target URIs ‘/unk.sh’ and ‘/se.sh’ and a combination of GET and POST requests to 185.221.154[.]208 with the User-Agent header ‘Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.51 Safari/537.36’ and the Target URIs, ‘/mg’, ‘/ki’, ‘/get’, ‘/h2’, ‘/ms’, and ‘/mu’. These network-based artefacts have been observed in previous Kinsing infections [13].

Figure 12: Event Log data for an Ivanti Sentry system showing the device displaying likely Kinsing C2 activity.

On customer environments where RESPOND was active, Darktrace was able to take swift autonomous action by blocking cryptomining connection attempts to malicious command-and-control (C2) infrastructure, in this case Kinsing servers.

Figure 13: Event Log data for an Ivanti Sentry server showing the device receiving a RESPOND action after attempting to contact Kinsing C2 infrastructure.

Fortunately, due to Darktrace DETECT+RESPOND prompt identification and targeted actions against these emerging threats, coupled with remediating steps taken by affected customers’ security teams, neither the cryptocurrency mining activities nor the network reconnaissance activities led to significant disruption.

Figure 14: Timeline of observed malicious activities.

Conclusion The inevitable presence of critical vulnerabilities in internet-facing systems underscores the perpetual challenge of defending against malicious intrusions. The near inexhaustible supply of entry routes into organizations’ networks available to malicious actors necessitates a more proactive and vigilant approach to network security.

While it is, of course, essential for organizations to secure their digital environments through the regular patching of software and keeping abreast of developing vulnerabilities that could impact their network, it is equally important to have a safeguard in place to mitigate against attackers who do manage to exploit newly discovered vulnerabilities.

In the case of Ivanti Sentry, Darktrace observed malicious actors validating exploits against affected servers on customer networks just a few days after the public disclosure of the critical vulnerability. This activity was followed up by a variety of malicious and disruptive, activities including cryptocurrency mining and internal network reconnaissance.

Darktrace DETECT immediately detected post-exploitation activities on compromised Ivanti Sentry servers, enabling security teams to intervene at the earliest possible stage. Darktrace RESPOND, when active, autonomously inhibited detected post-exploitation activities. These DETECT detections, along with their accompanying RESPOND interventions, prevented malicious actors from being able to progress further towards their likely harmful objectives.

Credit to Sam Lister, Senior Cyber Analyst, and Trent Kessler, SOC Analyst

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Appendices

MITRE ATT&CK Mapping

Initial Access techniques:

Exploit Public-Facing Application (T1190)

Credential Access techniques:

Unsecured Credentials: Credentials In Files (T1552.001)
Adversary-in-the-Middle: LLMNR/NBT-NS Poisoning and SMB Relay (T1557.001)

Discovery

Network Service Discovery (T1046)
Remote System Discovery (T1018)
Account Discovery: Domain Account (T1087.002)

Command and Control techniques:

Application Layer Protocol: Web Protocols (T1071.001)
Ingress Tool Transfer (T1105)
Non-Standard Port (T1571)
Encrypted Channel: Asymmetric Cryptography (T1573.002)

Impact techniques

Resource Hijacking (T1496)

List of IoCs

Exploit testing IoCs:

· 34.77.65[.]112

· Wget/1.14 (linux-gnu)

· cjjovo7mhpt7geo8aqlgxp7ypod6dqaiz.oast[.]site • 178.128.16[.]97

· curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.27.1 zlib/1.2.3 libidn/1.18 libssh2/1.4.2

· cjk45q1chpqflh938kughtrfzgwiofns3.oast[.]site • 178.128.16[.]97

· curl/7.29.0

Kinsing-related IoCs:

· 185.122.204[.]197

· /unk.sh

· /se.sh

· 185.221.154[.]208

· 185.221.154[.]208

· 45.15.158[.]124

· Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.51 Safari/537.36

· /mg

· /ki

· /get

· /h2

· /ms

· /mu

· vocaltube[.]ru • 185.154.53[.]140

· 92.255.110[.]4

· 194.87.254[.]160

Responder-related IoCs:

· 78.128.113[.]130

· 78.128.113[.]34

· /awp.tar.gz

· /ivanty

· /resp.tar.gz

Crypto-miner related IoCs:

· 140.228.24[.]160

· aelix[.]xyz • 104.21.60[.]147 / 172.67.197[.]200

· c8446f59cca2149cb5f56ced4b448c8d (JA3 client fingerprint)

· b5eefe582e146aed29a21747a572e11c (JA3 client fingerprint)

· pool.supportxmr[.]com

· xmr.2miners[.]com

· xmr.2miners[.]com

· monerooceans[.]stream

· xmr-eu2.nanopool[.]org

Port scanner-related IoCs:

· 122.161.66[.]161

· 192.241.235[.]32

· 45.86.162[.]147

· /ncat

· Wget/1.14 (linux-gnu)

· 45.159.248[.]179

· 142.93.115[.]146

· 23.92.29[.]148

· /TxPortMap

· 195.123.240.183

· 6935a8d379e086ea1aed159b8abcb0bc8acf220bd1cbc0a84fd806f14014bca7 (SHA256 hash of downloaded file)

Darktrace DETECT Model Breaches

· Anomalous Server Activity / New User Agent from Internet Facing System

· Device / New User Agent

· Anomalous Connection / New User Agent to IP Without Hostname

· Device / New User Agent and New IP

· Anomalous Connection / Application Protocol on Uncommon Port

· Anomalous Connection / Callback on Web Facing Device

· Compromise / High Volume of Connections with Beacon Score

· Compromise / Large Number of Suspicious Failed Connections

· Compromise / High Volume of Connections with Beacon Score

· Compromise / Beacon for 4 Days

· Compromise / Agent Beacon (Short Period)

· Device / Large Number of Model Breaches

· Anomalous Server Activity / Rare External from Server

· Compromise / Large Number of Suspicious Successful Connections

· Compromise / Monero Mining

· Compromise / High Priority Crypto Currency Mining

· Compromise / Sustained TCP Beaconing Activity To Rare Endpoint

· Device / Internet Facing Device with High Priority Alert

· Device / Suspicious SMB Scanning Activity

· Device / Internet Facing Device with High Priority Alert

· Device / Network Scan

· Device / Unusual LDAP Bind and Search Activity

· Compliance / Vulnerable Name Resolution

· Device / Anomalous SMB Followed By Multiple Model Breaches

· Device / New User Agent To Internal Server

· Anomalous Connection / Suspicious HTTP Activity

· Anomalous Connection / Unusual Internal Connections

· Anomalous Connection / Suspicious HTTP Activity

· Device / RDP Scan

· Device / Large Number of Model Breaches

· Compromise / Beaconing Activity To External Rare

· Compromise / Beacon to Young Endpoint

· Anomalous Connection / Suspicious HTTP Activity

· Compromise / Suspicious Internal Use Of Web Protocol

· Anomalous File / EXE from Rare External Location

· Anomalous File / Internet Facing System File Download

· Device / Suspicious SMB Scanning Activity

· Device / Internet Facing Device with High Priority Alert

· Device / Network Scan

· Device / Initial Breach Chain Compromise

References

[1] https://www.mnemonic.io/resources/blog/ivanti-endpoint-manager-mobile-epmm-authentication-bypass-vulnerability/
‍[2] https://www.mnemonic.io/resources/blog/threat-advisory-remote-file-write-vulnerability-in-ivanti-epmm/
‍[3] https://www.mnemonic.io/resources/blog/threat-advisory-remote-code-execution-vulnerability-in-ivanti-sentry/
‍[4] https://www.ivanti.com/blog/cve-2023-35078-new-ivanti-epmm-vulnerability
‍[5] https://forums.ivanti.com/s/article/CVE-2023-35078-Remote-unauthenticated-API-access-vulnerability?language=en_US
‍[6] https://forums.ivanti.com/s/article/KB-Remote-unauthenticated-API-access-vulnerability-CVE-2023-35078?language=en_US
‍[7] https://www.ivanti.com/blog/cve-2023-35081-new-ivanti-epmm-vulnerability
‍[8] https://forums.ivanti.com/s/article/CVE-2023-35081-Arbitrary-File-Write?language=en_US
‍[9] https://forums.ivanti.com/s/article/KB-Arbitrary-File-Write-CVE-2023-35081?language=en_US
‍[10] https://www.ivanti.com/blog/cve-2023-38035-vulnerability-affecting-ivanti-sentry
‍[11] https://forums.ivanti.com/s/article/CVE-2023-38035-API-Authentication-Bypass-on-Sentry-Administrator-Interface?language=en_US
‍[12] https://forums.ivanti.com/s/article/KB-API-Authentication-Bypass-on-Sentry-Administrator-Interface-CVE-2023-38035?language=en_US
‍[13] https://isc.sans.edu/diary/Your+Business+Data+and+Machine+Learning+at+Risk+Attacks+Against+Apache+NiFi/29900

INSIDE THE SOC

Darktrace cyber analysts are world-class experts in threat intelligence, threat hunting and incident response, and provide 24/7 SOC support to thousands of Darktrace customers around the globe. Inside the SOC is exclusively authored by these experts, providing analysis of cyber incidents and threat trends, based on real-world experience in the field.

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Sam Lister

SOC Analyst

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Appleby law firm uses Darktrace and Microsoft for proactive cyber resilience and compliance

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May 2024

Security Challenges for Appleby law firm

Appleby is an international law firm that provides offshore legal advice to clients. As such, assuring confidentiality is one of our priorities. I regularly discuss cybersecurity with our clients and prospects who want to know that their data will be protected.

Like all security teams, we are working to keep ahead of the evolving cyber threat landscape while also managing our internal tools and infrastructure.

Although we already applied security philosophies like defense-in-depth and multi-tiered protection, we wanted to expand our coverage especially given the increase in working from home. These improvements would be especially impactful given our lean security team, which must provide 24/7 coverage for our 10 offices around the globe that span several jurisdictions and time zones.

Given these challenges and goals, we turned to Darktrace.

Going beyond an XDR with Darktrace and Microsoft

We wanted to move away from point solutions, and after doing extensive research, we chose to consolidate around Darktrace and Microsoft. This helped us achieve increased coverage, seamless security operations, and even reduced costs.

While considering our upgrade from E3 to E5, we went through an extensive TCO exercise. After reviewing our stack, we were able to sunset legacy tools and consolidate our vendors into an integrated and cost-efficient modern platform built around Darktrace and Microsoft. We now have a single portal to manage security for all our coverage areas, improving upon what we had with our legacy eXtended Detection and Response (XDR) tool.

Darktrace’s AI-led understanding of our business operations, people, processes, and technology has helped us automate so our small team can easily achieve continuous detection, investigation, and response across our systems. This has helped us save time and overcome resource limitations, giving us comprehensive cyber resilience and new opportunities to move past firefighting to take proactive measures that harden our environment.

Darktrace and Microsoft have allowed us to simplify workflows and reduce costs without compromising security. In fact, it’s now stronger than ever.

Proactive protection with Darktrace PREVENT/Attack Surface Management™

I come from a physical security background, so I’ve always been keen on the prevention side. You would always rather prevent somebody from entering in the first place than deal with them once they are inside. With that mindset, we’re pushing our strongest controls to the boundary to stop threat actors before they gain access to our systems.

To help us with that, we use Darktrace PREVENT/Attack Surface Management™ (ASM). With just our brand name, it was able to reveal our entire attack surface, including shadow IT we didn’t know was there. PREVENT/ASM continuously monitors our exposures with AI and reports its findings to my team with actionable insights that contain key metrics and prioritizations based on critical risk. This enables us to maximize our impact with limited time and resources.

PREVENT/ASM has already identified typo squatting domains that threat actors set up to impersonate our brand in phishing attacks. Finding this type of brand abuse not only defends our company from attackers who could damage our reputation, but also protects our clients and vendors who could be targeted with these imitations. PREVENT/ASM even collects the necessary data needed for my team to file a Notice and Takedown order.

In addition to finding vulnerabilities such as brand abuse, PREVENT/ASM integrates with our other Darktrace products to give us platform-wide coverage. This is key because an attacker will never hit only one point, they’re going to hit a sequence of targets to try to get in.

Now, we can easily understand vulnerabilities and attacks because of the AI outputs flowing across the Darktrace platform as part of the comprehensive, interconnected system. I have already made a practice of seeing an alert in Darktrace DETECT/Network and clicking through to the PREVENT/ASM interface to get more context.

Achieving compliance standards for our clients

We work hard to ensure confidentiality for our clients and prospects and we also frequently work with regulated entities, so we must demonstrate that we have controls in place.

With Darktrace in our security stack, we have 24/7 coverage and can provide evidence of how autonomous responses have successfully blocked malicious activity in the past. When I have demonstrated how Darktrace works to regulators, it ticks several of their boxes. Our Darktrace coverage has been critical in helping us achieve ISO27001 compliance, the world’s best-known standard for information security management systems.

Darktrace continues to prove its value. Last year, we brought a red team into our office for penetration testing. As soon as the first tester plugged into our network, Darktrace shut him out. We spent hours clearing the alerts and blocks to let the red team continue working, which validated that Darktrace stopped them at every step.

The red team reported that our controls are effective and even in the top 10% of all companies they had ever tested. That feedback, when presented to ISO auditors, regulators, and clients, immediately answers a lot of their more arduous questions and concerns.

Darktrace helps us meet compliance frameworks while reassuring both my team and our clients that our digital infrastructure is safe.

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About the author

Michael Hughes

CISO, Appleby (guest contributor)

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Inside the SOC

Detecting Attacks Across Email, SaaS, and Network Environments with Darktrace’s AI Platform Approach

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Apr 2024

The State of AI in Cybersecurity

In a recent survey outlined in Darktrace’s State of AI Cyber Security whitepaper, 95% of cyber security professionals agree that AI-powered security solutions will improve their organization’s detection of cyber-threats [1]. Crucially, a combination of multiple AI methods is the most effective to improve cybersecurity; improving threat detection, accelerating threat investigation and response, and providing visibility across an organization’s digital environment.

In March 2024, Darktrace’s AI-led security platform was able to detect suspicious activity affecting a customer’s email, Software-as-a-Service (SaaS), and network environments, whilst its applied supervised learning capability, Cyber AI Analyst, autonomously correlated and connected all of these events together in one single incident, explained concisely using natural language processing.

Attack Overview

Following an initial email attack vector, an attacker logged into a compromised SaaS user account from the Netherlands, changed inbox rules, and leveraged the account to send thousands of phishing emails to internal and external users. Internal users fell victim to the emails by clicking on contained suspicious links that redirected them to newly registered suspicious domains hosted on same IP address as the hijacked SaaS account login. This activity triggered multiple alerts in Darktrace DETECT™ on both the network and SaaS side, all of which were correlated into one Cyber AI Analyst incident.

In this instance, Darktrace RESPOND™ was not active on any of the customer’s environments, meaning the compromise was able to escalate until their security team acted on the alerts raised by DETECT. Had RESPOND been enabled at the time of the attack, it would have been able to apply swift actions to contain the attack by blocking connections to suspicious endpoints on the network side and disabling users deviating from their normal behavior on the customer’s SaaS environment.

Nevertheless, thanks to DETECT and Cyber AI Analyst, Darktrace was able to provide comprehensive visibility across the customer’s three digital estate environments, decreasing both investigation and response time which enabled them to quickly enact remediation during the attack. This highlights the crucial role that Darktrace’s combined AI approach can play in anomaly detection cyber defense

Attack Details & Darktrace Coverage

Attack timeline

1. Email: the initial attack vector

The initial attack vector was likely email, as on March 18, 2024, Darktrace observed a user device making several connections to the email provider “zixmail[.]net”, shortly before it connected to the first suspicious domain. Darktrace/Email identified multiple unusual inbound emails from an unknown sender that contained a suspicious link. Darktrace recognized these emails as potentially malicious and locked the link, ensuring that recipients could not directly click it.

Suspected initial compromise email from an unknown sender, containing a suspicious link, which was locked by Darktrace/Email. — Figure 1: Suspected initial compromise email from an unknown sender, containing a suspicious link, which was locked by Darktrace/Email.

2. Escalation to Network

Later that day, despite Darktrace/Email having locked the link in the suspicious email, the user proceeded to click on it and was directed to a suspicious external location, namely “rz8js7sjbef[.]latovafineart[.]life”, which triggered the Darktrace/Network DETECT model “Suspicious Domain”. Darktrace/Email was able to identify that this domain had only been registered 4 days before this activity and was hosted on an IP address based in the Netherlands, 193.222.96[.]9.

3. SaaS Account Hijack

Just one minute later, Darktrace/Apps observed the user’s Microsoft 365 account logging into the network from the same IP address. Darktrace understood that this represented unusual SaaS activity for this user, who had only previously logged into the customer’s SaaS environment from the US, triggering the “Unusual External Source for SaaS Credential Use” model.

4. SaaS Account Updates

A day later, Darktrace identified an unusual administrative change on the user’s Microsoft 365 account. After logging into the account, the threat actor was observed setting up a new multi-factor authentication (MFA) method on Microsoft Authenticator, namely requiring a 6-digit code to authenticate. Darktrace understood that this authentication method was different to the methods previously used on this account; this, coupled with the unusual login location, triggered the “Unusual Login and Account Update” DETECT model.

5. Obfuscation Email Rule

On March 20, Darktrace detected the threat actor creating a new email rule, named “…”, on the affected account. Attackers are typically known to use ambiguous or obscure names when creating new email rules in order to evade the detection of security teams and endpoints users.

The parameters for the email rule were:

“AlwaysDeleteOutlookRulesBlob: False, Force: False, MoveToFolder: RSS Feeds, Name: ..., MarkAsRead: True, StopProcessingRules: True.”

This rule was seemingly created with the intention of obfuscating the sending of malicious emails, as the rule would move sent emails to the "RSS Feeds” folder, a commonly used tactic by attackers as the folder is often left unchecked by endpoint users. Interestingly, Darktrace identified that, despite the initial unusual login coming from the Netherlands, the email rule was created from a different destination IP, indicating that the attacker was using a Virtual Private Network (VPN) after gaining a foothold in the network.

Hijacked SaaS account making an anomalous login from the unusual Netherlands-based IP, before creating a new email rule. — Figure 2: Hijacked SaaS account making an anomalous login from the unusual Netherlands-based IP, before creating a new email rule.

6. Outbound Phishing Emails Sent

Later that day, the attacker was observed using the compromised customer account to send out numerous phishing emails to both internal and external recipients. Darktrace/Email detected a significant spike in inbound emails on the compromised account, with the account receiving bounce back emails or replies in response to the phishing emails. Darktrace further identified that the phishing emails contained a malicious DocSend link hidden behind the text “Click Here”, falsely claiming to be a link to the presentation platform Prezi.

Figure 3: Darktrace/Email detected that the DocSend link displayed via text “Click Here”, was embedded in a Prezi link.

7. Suspicious Domains and Redirects

After the phishing emails were sent, multiple other internal users accessed the DocSend link, which directed them to another suspicious domain, “thecalebgroup[.]top”, which had been registered on the same day and was hosted on the aforementioned Netherlands-based IP, 193.222.96[.]91. At the time of the attack, this domain had not been reported by any open-source intelligence (OSINT), but it has since been flagged as malicious by multiple vendors [2].

External Sites Summary showing the suspicious domain that had never previously been seen on the network. A total of 11 “Suspicious Domain” models were triggered in response to this activity. — Figure 4: External Sites Summary showing the suspicious domain that had never previously been seen on the network. A total of 11 “Suspicious Domain” models were triggered in response to this activity.

8. Cyber AI Analyst’s Investigation

As this attack was unfolding, Darktrace’s Cyber AI Analyst was able to autonomously investigate the events, correlating them into one wider incident and continually adding a total of 14 new events to the incident as more users fell victim to the phishing links.

Cyber AI Analyst successfully weaved together the initial suspicious domain accessed in the initial email attack vector (Figure 5), the hijack of the SaaS account from the Netherlands IP (Figure 6), and the connection to the suspicious redirect link (Figure 7). Cyber AI Analyst was also able to uncover other related activity that took place at the time, including a potential attempt to exfiltrate data out of the customer’s network.

By autonomously analyzing the thousands of connections taking place on a network at any given time, Darktrace’s Cyber AI Analyst is able to detect seemingly separate anomalous events and link them together in one incident. This not only provides organizations with full visibility over potential compromises on their networks, but also saves their security teams precious time ensuring they can quickly scope out the ongoing incident and begin remediation.

Figure 5: Cyber AI Analyst correlated the attack’s sequence, starting with the initial suspicious domain accessed in the initial email attack vector.

Figure 6: As the attack progressed, Cyber AI Analyst correlated and appended additional events to the same incident, including the SaaS account hijack from the Netherlands-based IP.

Cyber AI Analyst correlated and appended additional events to the same incident, including additional users connecting to the suspicious redirect link following the outbound phishing emails being sent. — Figure 7: Cyber AI Analyst correlated and appended additional events to the same incident, including additional users connecting to the suspicious redirect link following the outbound phishing emails being sent.

Conclusion

In this scenario, Darktrace demonstrated its ability to detect and correlate suspicious activities across three critical areas of a customer’s digital environment: email, SaaS, and network.

It is essential that cyber defenders not only adopt AI but use a combination of AI technology capable of learning and understanding the context of an organization’s entire digital infrastructure. Darktrace’s anomaly-based approach to threat detection allows it to identify subtle deviations from the expected behavior in network devices and SaaS users, indicating potential compromise. Meanwhile, Cyber AI Analyst dynamically correlates related events during an ongoing attack, providing organizations and their security teams with the information needed to respond and remediate effectively.

Credit to Zoe Tilsiter, Analyst Consulting Lead (EMEA), Brianna Leddy, Director of Analysis

Appendices

References

[1] https://darktrace.com/state-of-ai-cyber-security

[2] https://www.virustotal.com/gui/domain/thecalebgroup.top

Darktrace DETECT Model Coverage

SaaS Models

- SaaS / Access / Unusual External Source for SaaS Credential Use

- SaaS / Compromise / Unusual Login and Account Update

- SaaS / Compliance / Anomalous New Email Rule

- SaaS / Compromise / Unusual Login and New Email Rule

Network Models

- Device / Suspicious Domain

- Multiple Device Correlations / Multiple Devices Breaching Same Model

Cyber AI Analyst Incidents

- Possible Hijack of Office365 Account

- Possible SSL Command and Control

Indicators of Compromise (IoCs)

IoC – Type – Description

193.222.96[.]91 – IP – Unusual Login Source

thecalebgroup[.]top – Domain – Possible C2 Endpoint

rz8js7sjbef[.]latovafineart[.]life – Domain – Possible C2 Endpoint

https://docsend[.]com/view/vcdmsmjcskw69jh9 - Domain - Phishing Link

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About the author

Zoe Tilsiter

Cyber Analyst

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