Darktrace threat finds: Abusing off-the-shelf tools to deploy ransomware
16
Aug 2020
16
Aug 2020
The increased use of off-the-shelf tools is lowering the barrier to entry for cyber-criminals. This blog explores an incident in which a low-skilled threat actor was able to successfully deploy ransomware in a retail organization by connecting to the domain controller.
Key takeaways
A retail organization based in Africa was recently targeted with ransomware
The general lack of obfuscation and use of no custom malware suggest a low-level threat actor
Threat actors of all levels increasingly use common administrative tools such as PsExec for stealth purposes
The company was relatively small, but no organization is immune to being targeted by ransomware
Attack details
Darktrace recently detected a form of ransomware at an African retailer. In the threat find that follows, the attacker connected to the organization’s domain controllers via a commonly used administrative tool and then began communicating to another C2 host.
Approximately an hour after the initial beaconing behavior, unusual RDP/SMB occurred on the network, followed by unusual service control activity. Darktrace detected each stage of the attack’s life cycle and would have automatically neutralized the attack had Darktrace Antigena been configured in active mode. However, because Autonomous Response was set up in passive mode, requiring confirmation from the human security team, the attack was able to escalate past its opening stages.
The ransomware activity commenced over the weekend, four days after the first beaconing activity. The timeline of the attack is shown below.
Timeline of attack: Overall dwell time around seven days
Figure 1: A timeline of events
How did the attack bypass the rest of the security stack?
This attack abused off-the-shelf tools that were already used by the client. This tactic, which targeted the domain controller as the initial vector, made the malware deployment easy and effective.
AI Analyst coverage
Darktrace’s Cyber AI analyst identified that the SQL server was writing a number of unusual files to shared drives, which appear to have specifically been binary executables for deployment of ransomware.
Figure 2: Darktrace’s Cyber AI Analyst revealing the unusual files
Overview of infected device
The graph below details the anomalous connections and other forms of unusual activity that occurred over a 10-hour period. Darktrace’s Enterprise Immune system first detected this activity in the compliance/remote management tool on the server, and then saw it spread laterally to other devices within the organization’s cyber-ecosystem.
Figure 3: A graph showing the number of external connections on the domain controller and anomalies detected
Concluding thoughts
In this attack, the C2 domain has an accessible array of standard PHP, including /phpMyAdmin and /p.php. The latter details the server time to be UTC+8, the time zone of mainland China.
Figure 4: The C2 domain
Here, multiple factors suggest a lower-level threat actor, including the lack of obfuscation, the reliance on off-the-shelf tools, and the comparatively small size of the target organization. With the rise of Ransomware-as-a-Service (RaaS), automated domain generation, and other tools that lower the barrier to entry for attackers, it comes as no surprise that even a low-level threat actor could breach a corporate network. This also means that smaller organizations that would have been ignored by advanced cyber-criminals may find themselves targeted by attacks launched by low-level threat actors.
Indeed, convenient and widely used tools can often be abused for access, and the tools for ransomware are fairly common and easy to deploy once a foothold has been established. This calls for a proactive response to cyber security, and full visibility into networks, to be able to spot and stop threats before they escalate into crisis.
Deploying ransomware over the weekend is a common technique to maximize chances of success for the attacker, as response times from security teams are generally slower. This falls into a broader trend of ‘out of hours’ attacks that are becoming increasingly common and shines a light on the need for defensive technology that can act autonomously and contain a threat without relying on humans. With over a dozen AI models firing, there is no doubt that in this case Darktrace’s Autonomous Response technology would have taken a targeted and proportionate response to contain the threat. In addition to Autonomous Response, AI that can investigate an incident and provide actionable intelligence so a security team can quickly take action to fully remediate an incident or address a vulnerability is critical to staying ahead of fast-changing threats.
Thanks to Darktrace analyst Roberto Romeu for his insights on the above threat find.
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.
AUTHOR
ABOUT ThE AUTHOR
Max Heinemeyer
Chief Product Officer
Max is a cyber security expert with over a decade of experience in the field, specializing in a wide range of areas such as Penetration Testing, Red-Teaming, SIEM and SOC consulting and hunting Advanced Persistent Threat (APT) groups. At Darktrace, Max is closely involved with Darktrace’s strategic customers & prospects. He works with the R&D team at Darktrace, shaping research into new AI innovations and their various defensive and offensive applications. Max’s insights are regularly featured in international media outlets such as the BBC, Forbes and WIRED. Max holds an MSc from the University of Duisburg-Essen and a BSc from the Cooperative State University Stuttgart in International Business Information Systems.
Darktrace has been named as Microsoft UK Partner of the Year for 2024! The Microsoft Partner Awards recognize winners for their commitment to customers, impact of solutions, and exemplary use of Microsoft technologies.
Whilst the award was granted based on our innovations combining Darktrace/Email and Microsoft Defender for Office 365, our shared values go beyond technology. Darktrace stood out for the integration of our products to deliver exceptional security value to customers, as well as our investment in partnerships, marketplace and go to market. Microsoft was also impressed with our strong commitment to diversity and inclusion and our broader contribution to both the UK economy and the UK tech sector.
Microsoft Defender for Office 365 + Darktrace/Email leave attackers nowhere to hide
The email threat landscape is constantly evolving. Attacks are becoming more sophisticated, more targeted and increasing in multi-stage payload attacks. Across the Darktrace customer base in 2023 alone, we have seen a 135% increase in ‘novel social engineering attacks’, corresponding with the rise of ChatGPT, 45% of phishing emails were identified as spear phishing attempts and a 59% increase in multi-stage payload attacks.
Legacy defenses were built to address a high volume of unsophisticated attacks, but generative AI has shifted the threats towards lower quantity yet very sophisticated, high impact targeted attacks. Microsoft Defender for Office 365’s rapid innovation has outpaced the Secure Email Gateway’s rule and signature based historical data approach. Customers no longer need email gateways which duplicate workflows and add expense native to their Defender for O365 solution.
Point email solutions overlap with Microsoft in 3 key areas: detection approach, workflows, capabilities
Detection - Microsoft receives trillions threat signals daily, giving customers the broadest scope of the attack landscape. Darktrace combined with Microsoft unites business and attack centric approaches
Workflows – any Microsoft configurations are reflected automatically in Darktrace/Email. Users can keep daily workflow in Microsoft, while a traditional SEG requires duplicated workflows
Capabilities – Microsoft handles foundational elements like archiving/encryption/signature matching while Darktrace handles advanced threat security
Darktrace/Email is built to elevate, not duplicate, Microsoft email security – removing the burden of operating legacy point solutions and blocking 25% more threats. Robust account takeover protections to stop the 38% of sophisticated threats other tools miss. Customers can seamlessly correlate activity and insights across Microsoft email, DMARC and Teams to stop threats on average 13 days earlier.
Azure Marketplace
Microsoft Azure customers can access Darktrace in the Azure Marketplace to take advantage of the scalability, reliability, and agility of Azure to drive rapid IT operations and security integrations across the enterprise. Customers can leverage their Microsoft Azure Consumption Commitments (MACC), making procurement simple. As UK Partner of the Year winner, customers know they have a trusted partner with Darktrace and a proven solution to work seamlessly with Azure.
Following up on our Conversation: Detecting & Containing a LinkedIn Phishing Attack with Darktrace
25
Jun 2024
Note: Real organization, domain and user names have been modified and replaced with fictitious names to maintain anonymity.
Social media cyber-attacks
Social media is a known breeding ground for cyber criminals to easily connect with a near limitless number of people and leverage the wealth of personal information shared on these platforms to defraud the general public. Analysis suggests even the most tech savvy ‘digital natives’ are vulnerable to impersonation scams over social media, as criminals weaponize brands and trends, using the promise of greater returns to induce sensitive information sharing or fraudulent payments [1].
LinkedIn phishing
As the usage of a particular social media platform increases, cyber criminals will find ways to exploit the increasing user base, and this trend has been observed with the rise in LinkedIn scams in recent years [2]. LinkedIn is the dominant professional networking site, with a forecasted 84.1million users by 2027 [3]. This platform is data-driven, so users are encouraged to share information publicly, including personal life updates, to boost visibility and increase job prospects [4] [5]. While this helps legitimate recruiters to gain a good understanding of the user, an attacker could also leverage the same personal content to increase the sophistication and success of their social engineering attempts.
Darktrace detection of LinkedIn phishing
Darktrace detected a Software-as-a-Service (SaaS) compromise affecting a construction company, where the attack vector originated from LinkedIn (outside the monitoring of corporate security tools), but then pivoted to corporate email where a credential harvesting payload was delivered, providing the attacker with credentials to access a corporate file storage platform.
Because LinkedIn accounts are typically linked to an individual’s personal email and are most commonly accessed via the mobile application [6] on personal devices that are not monitored by security teams, it can represent an effective initial access point for attackers looking to establish an initial relationship with their target. Moreover, user behaviors to ignore unsolicited emails from new or unknown contacts are less frequently carried over to platforms like LinkedIn, where interactions with ‘weak ties’ as opposed to ‘strong ties’ are a better predictor of job mobility [7]. Had this attack been allowed to continue, the threat actor could have leveraged access to further information from the compromised business cloud account to compromise other high value accounts, exfiltrate sensitive data, or defraud the organization.
LinkedIn phishing attack details
Reconnaissance
The initial reconnaissance and social engineering occurred on LinkedIn and was thus outside the purview of corporate security tools, Darktrace included.
However, the email domain “hausconstruction[.]com” used by the attacker in subsequent communications appears to be a spoofed domain impersonating a legitimate construction company “haus[.]com”, suggesting the attacker may have also impersonated an employee of this construction company on LinkedIn. In addition to spoofing the domain, the attacker seemingly went further to register “hausconstruction.com” on a commercial web hosting platform. This is a technique used frequently not just to increase apparent legitimacy, but also to bypass traditional security tools since newly registered domains will have no prior threat intelligence, making them more likely to evade signature and rules-based detections [8]. In this instance, open-source intelligence (OSINT) sources report that the domain was created several months earlier, suggesting this may have been part of a targeted attack on construction companies.
Initial Intrusion
It was likely that during the correspondence over LinkedIn, the target user was solicited into following up over email regarding a prospective construction project, using their corporate email account. In a probable attempt to establish a precedent of bi-directional correspondence so that subsequent malicious emails would not be flagged by traditional security tools, the attacker did not initially include suspicious links, attachments or use solicitous or inducive language within their initial emails.
Figure 1: Example of bi-directional email correspondence between the target and the attacker impersonating a legitimate employee of the construction company haus.com.
Figure 2: Cyber AI Analyst investigation into one of the initial emails the target received from the attacker.
To accomplish the next stage of their attack, the attacker shared a link, hidden behind the inducing text “VIEW ALL FILES”, to a malicious file using the Hightail cloud storage service. This is also a common method employed by attackers to evade detection, as this method of file sharing does not involve attachments that can be scanned by traditional security tools, and legitimate cloud storage services are less likely to be blocked.
OSINT analysis on the malicious link link shows the file hosted on Hightail was a HTML file with the associated message “Following up on our LinkedIn conversation”. Further analysis suggests the file contained obfuscated Javascript that, once opened, would automatically redirect the user to a malicious domain impersonating a legitimate Microsoft login page for credential harvesting purposes.
Figure 3: The malicious HTML file containing obfuscated Javascript, where the highlighted string references the malicious credential harvesting domain.
Figure 4: Screenshot of fraudulent Microsoft Sign In page hosted on the malicious credential harvesting domain.
Although there was prior email correspondence with the attacker, this email was not automatically deemed safe by Darktrace and was further analyzed for unusual properties and unusual communications for the recipient and the recipient’s peer group.
Darktrace determined that:
It was unusual for this file storage solution to be referenced in communications to the user and the wider network
Textual properties of the email body suggested a high level of inducement from the sender, with a high level of focus on the phishing link.
The full link contained suspicious properties suggesting it is high risk.
Figure 5: Darktrace’s analysis of the phishing email, presenting key information about the unusual characteristics of this email, information on highlighted content, and an overview of actions that were initially applied.
Based on these anomalies, Darktrace initially moved the phishing email to the junk folder and locked the link, preventing the user from directly accessing the malicious file hosted on Hightail. However, the customer’s security team released the email, likely upon end-user request, allowing the target user to access the file and ultimately enter their credentials into that credential harvesting domain.
Figure 6: Darktrace alerts triggered by the malicious phishing email and the corresponding Autonomous Response actions.
Lateral Movement
Correspondence between the attacker and target continued for two days after the credential harvesting payload was delivered. Five days later, Darktrace detected an unusual login using multi-factor authentication (MFA) from a rare external IP and ASN that coincided with Darktrace/Email logs showing access to the credential harvesting link.
This attempt to bypass MFA, known as an Office365 Shell WCSS attack, was likely achieved by inducing the target to enter their credentials and legitimate MFA token into the fake Microsoft login page. This was then relayed to Microsoft by the attacker and used to obtain a legitimate session. The attacker then reused the legitimate token to log into Exchange Online from a different IP and registered the compromised device for MFA.
Figure 7: Screenshot within Darktrace/Email of the phishing email that was released by the security team, showing the recipient clicked the link to file storage where the malicious payload was stored.
Figure 8: Event Log showing a malicious login and MFA bypass at 17:57:16, shortly after the link was clicked. Highlighted in green is activity from the legitimate user prior to the malicious login, using Edge. Highlighted in orange and red is the malicious activity using Chrome.
The IP addresses used by the attacker appear to be part of anonymization infrastructure, but are not associated with any known indicators of compromise (IoCs) that signature-based detections would identify [9] [10].
In addition to logins being observed within half an hour of each other from multiple geographically impossible locations (San Francisco and Phoenix), the unexpected usage of Chrome browser, compared to Edge browser previously used, provided Darktrace with further evidence that this activity was unlikely to originate from the legitimate user. Although the user was a salesperson who frequently travelled for their role, Darktrace’s Self-Learning AI understood that the multiple logins from these locations was highly unusual at the user and group level, and coupled with the subsequent unexpected account modification, was a likely indicator of account compromise.
Accomplish mission
Although the email had been manually released by the security team, allowing the attack to propagate, additional layers of defense were triggered as Darktrace's Autonomous Response initiated “Disable User” actions upon detection of the multiple unusual logins and the unauthorized registration of security information.
However, the customer had configured Autonomous Response to require human confirmation, therefore no actions were taken until the security team manually approved them over two hours later. In that time, access to mail items and other SharePoint files from the unusual IP address was detected, suggesting a potential loss of confidentiality to business data.
Figure 9: Advanced Search query showing several FilePreviewed and MailItemsAccessed events from either the IPs used by the attacker, or using the software Chrome. Note some of the activity originated from Microsoft IPs which may be whitelisted by traditional security tools.
However, it appears that the attacker was able to maintain access to the compromised account, as login and mail access events from 199.231.85[.]153 continued to be observed until the afternoon of the next day.
Conclusion
This incident demonstrates the necessity of AI to security teams, with Darktrace’s ActiveAI Security Platform detecting a sophisticated phishing attack where human judgement fell short and initiated a real-time response when security teams could not physically respond as fast.
Security teams are very familiar with social engineering and impersonation attempts, but these attacks remain highly prevalent due to the widespread adoption of technologies that enable these techniques to be deployed with great sophistication and ease. In particular, the popularity of information-rich platforms like LinkedIn that are geared towards connecting with unknown people make it an attractive initial access point for malicious attackers.
In the second half of 2023 alone, over 200 thousand fake profiles were reported by members on LinkedIn [11]. Fake profiles can be highly sophisticated, use professional images, contain compelling descriptions, reference legitimate company listings and present believable credentials.
It is unrealistic to expect end users to defend themselves against such sophisticated impersonation attempts. Moreover, it is extremely difficult for human defenders to recognize every fraudulent interaction amidst a sea of fake profiles. Instead, defenders should leverage AI, which can conduct autonomous investigations without human biases and limitations. AI-driven security can ensure successful detection of fraudulent or malicious activity by learning what real users and devices look like and identifying deviations from their learned behaviors that may indicate an emerging threat.
Appendices
Darktrace Model Detections
DETECT/ Apps
SaaS / Compromise / SaaS Anomaly Following Anomalous Login
SaaS / Compromise / Unusual Login and Account Update
