Blog
Einblicke in das SOC-Team
RESPOND
To be Xor Not to Be: How RESPOND could have stopped a surprise DDoS incident
When is the best time to be hit with a cyber-attack?
The answer that springs to most is ‘Never’, however in today’s threat landscape, this is often wishful thinking. The next best answer is ‘When we’re ready for it’. Yet, this does not take into account the intention of those committing attacks. The reality is that the best time for a cyber-attack is when no one else is around to stop it.
When do cyber attacks happen?
Previous analysis from Mandiant reveals that over half of ransomware compromises occur at out of work hours, a trend Darktrace has also witnessed in the past two years [1]. This is deliberate, as the fewer people that are online, the harder it is to get ahold of security teams and the higher the likelihood there is of an attacker achieving their goals. Given this landscape, it is clear that autonomous response is more important than ever. In the absence of human resources, autonomous security can fill in the gap long enough for IT teams to begin remediation.
This blog will detail an incident where autonomous response provided by Darktrace RESPOND would have entirely prevented an infection attempt, despite it occurring in the early hours of the morning. Because the customer had RESPOND in human confirmation mode (AI response must first be approved by a human), the attempt by XorDDoS was ultimately successful. Given that the attack occurred in the early hours of the morning, there was likely no one around to confirm Darktrace RESPOND actions and prevent the attack.
XorDDoS Primer
XorDDoS is a botnet, a type of malware that infects devices for the purpose of controlling them as a collective to carry out specific actions. In the case of XorDDoS, it infects devices in order to carry out denial of service attacks using said devices. This year, Microsoft has reported a substantial increase in activity from this malware strain, with an increased focus on Linux based operating systems [2]. XorDDoS most commonly finds its way onto systems via SSH brute-forcing, and once deployed, encrypts its traffic with an XOR cipher. XorDDoS has also been known to download additional payloads such as backdoors and cryptominers. Needless to say, this is not something you have on a corporate network.
Initial Intrusion of XorDDoS
The incident begins with a device first coming online on 10th August. The device appeared to be internet facing and Darktrace saw hundreds of incoming SSH connections to the device from a variety of endpoints. Over the course of the next five days, the device received thousands of failed SSH connections from several IP addresses that, according to OSINT, may be associated with web scanners [3]. Successful SSH connections were seen from internal IP addresses as well as IP addresses associated with IT solutions relevant to Asia-Pacific (the customer’s geographic location). On midnight of 15th August, the first successful SSH connection occurred from an IP address that has been associated with web scanning. This connection lasted around an hour and a half, and the external IP uploaded around 3.3 MB of data to the client device. Given all of this, and what the industry knows about XorDDoS, it is likely that the client device had SSH exposed to the Internet which was then brute-forced for initial access.
There were a few hours of dwell until the device downloaded a ZIP file from an Iraqi mirror site, mirror[.]earthlink[.]iq at around 6AM in the customer time zone. The endpoint had only been seen once before and was 100% rare for the network. Since there has been no information on OSINT around this particular endpoint or the ZIP files downloaded from the mirror site, the detection was based on the unusualness of the download.
Following this, Darktrace saw the device make a curl request to the external IP address 107.148.210[.]218. This was highlighted as the user agent associated with curl had not been seen on the device before, and the connection was made directly to an IP address without a hostname (suggesting that the connection was scripted). The URIs of these requests were ‘1.txt’ and ‘2.txt’.
The ‘.txt’ extensions on the URIs were deceiving and it turned out that both were executable files masquerading as text files. OSINT on both of the hashes revealed that the files were likely associated with XorDDoS. Additionally, judging from packet captures of the connection, the true file extension appeared to be ‘.ELF’. As XorDDoS primarily affects Linux devices, this would make sense as the true extension of the payload.
C2 Connections
Immediately after the ‘.ELF’ download, Darktrace saw the device attempting C2 connections. This included connections to DGA-like domains on unusual ports such as 1525 and 8993. Luckily, the client’s firewall seems to have blocked these connections, but that didn’t stop XorDDoS. XorDDoS continued to attempt connections to C2 domains, which triggered several Proactive Threat Notifications (PTNs) that were alerted by SOC. Following the PTNs, the client manually quarantined the device a few hours after the initial breach. This lapse in actioning was likely due to an early morning timing with the customer’s employees not being online yet. After the device was quarantined, Darktrace still saw XorDDoS attempting C2 connections. In all, hundreds of thousands of C2 connections were detected before the device was removed from the network sometime on 7th September.
An Alternate Timeline
Although the device was ultimately removed, this attack would have been entirely prevented had RESPOND/Network not been in human confirmation mode. Autonomous response would have kicked in once the device downloaded the ‘.ZIP file’ from the Iraqi mirror site and blocked all outgoing connections from the breach device for an hour:
The model breach in Figure 3 would have prevented the download of the XorDDoS executables, and then prevented the subsequent C2 connections. This hour would have been crucial, as it would have given enough time for members of the customer’s security team to get back online should the compromised device have attempted anything else. With everyone attentive, it is unlikely that this activity would have lasted as long as it did. Had the attack been allowed to progress further, the infected device would have at the very least been an unwilling participant in a future DDoS attack. Additionally, the device could have a backdoor placed within it, and additional malware such as cryptojackers might have been deployed.
Conclusions
Unfortunately, we do not exist in the alternate timeline that autonomous response would have prevented this whole series of events.Luckily, although it was not in place, the PTN alerts provided by Darktrace’s SOC team still sped up the process of remediation in an event that was never intended to be discovered given the time it occurred. Unusual times of attack are not just limited to ransomware, so organizations need to have measures in place for the times that are most inconvenient to them, but most convenient to attackers. With Darktrace/RESPOND however, this is just one click away.
Thanks to Brianna Leddy for their contribution.
Appendices
Darktrace Model Detections
Below is a list of model breaches in order of trigger. The Proactive Threat Notification models are in bold and only the first Antigena [RESPOND] breach that would have prevented the initial compromise has been included. A manual quarantine breach has also been added to show when the customer began remediation.
- Compliance / Incoming SSH, August 12th 23:39 GMT +8
- Anomalous File / Zip or Gzip from Rare External Location, August 15th, 6:07 GMT +8
- Antigena / Network / External Threat / Antigena File then New Outbound Block, August 15th 6:36 GMT +8 [part of the RESPOND functionality]
- Anomalous Connection / New User Agent to IP Without Hostname, August 15th 6:59 GMT +8
- Anomalous File / Numeric Exe Download, August 15th 6:59 GMT +8
- Anomalous File / Masqueraded File Transfer, August 15th 6:59 GMT +8
- Anomalous File / EXE from Rare External Location, August 15th 6:59 GMT +8
- Device / Internet Facing Device with High Priority Alert, August 15th 6:59 GMT +8
- Compromise / Rare Domain Pointing to Internal IP, August 15th 6:59 GMT +8
- Device / Initial Breach Chain Compromise, August 15th 6:59 GMT +8
- Compromise / Large Number of Suspicious Failed Connections, August 15th 7:01 GMT +8
- Compromise / High Volume of Connections with Beacon Score, August 15th 7:04 GMT +8
- Compromise / Fast Beaconing to DGA, August 15th 7:04 GMT +8
- Compromise / Suspicious File and C2, August 15th 7:04 GMT +8
- Antigena / Network / Manual / Quarantine Device, August 15th 8:54 GMT +8 [part of the RESPOND functionality]
List of IOCs
MITRE ATT&CK Mapping
Reference List
[1] They Come in the Night: Ransomware Deployment Trends
[2] Rise in XorDdos: A deeper look at the stealthy DDoS malware targeting Linux devices
[3] Alien Vault: Domain Navicatadvvr & https://www.virustotal.com/gui/domain/navicatadvvr.com & https://maltiverse.com/hostname/navicatadvvr.com
Sie mögen das und wollen mehr?
More in this series
Blog
Einblicke in das SOC-Team
PurpleFox in a Henhouse: How Darktrace Hunted Down a Persistent and Dynamic Rootkit
Versatile Malware: PurpleFox
As organizations and security teams across the world move to bolster their digital defenses against cyber threats, threats actors, in turn, are forced to adopt more sophisticated tactics, techniques and procedures (TTPs) to circumvent them. Rather than being static and predictable, malware strains are becoming increasingly versatile and therefore elusive to traditional security tools.
One such example is PurpleFox. First observed in 2018, PurpleFox is a combined fileless rootkit and backdoor trojan known to target Windows machines. PurpleFox is known for consistently adapting its functionalities over time, utilizing different infection vectors including known vulnerabilities (CVEs), fake Telegram installers, and phishing. It is also leveraged by other campaigns to deliver ransomware tools, spyware, and cryptocurrency mining malware. It is also widely known for using Microsoft Software Installer (MSI) files masquerading as other file types.
The Evolution of PurpleFox
The Original Strain
First reported in March 2018, PurpleFox was identified to be a trojan that drops itself onto Windows machines using an MSI installation package that alters registry values to replace a legitimate Windows system file [1]. The initial stage of infection relied on the third-party toolkit RIG Exploit Kit (EK). RIG EK is hosted on compromised or malicious websites and is dropped onto the unsuspecting system when they visit browse that site. The built-in Windows installer (MSIEXEC) is leveraged to run the installation package retrieved from the website. This, in turn, drops two files into the Windows directory – namely a malicious dynamic-link library (DLL) that acts as a loader, and the payload of the malware. After infection, PurpleFox is often used to retrieve and deploy other types of malware.
Subsequent Variants
Since its initial discovery, PurpleFox has also been observed leveraging PowerShell to enable fileless infection and additional privilege escalation vulnerabilities to increase the likelihood of successful infection [2]. The PowerShell script had also been reported to be masquerading as a .jpg image file. PowerSploit modules are utilized to gain elevated privileges if the current user lacks administrator privileges. Once obtained, the script proceeds to retrieve and execute a malicious MSI package, also masquerading as an image file. As of 2020, PurpleFox no longer relied on the RIG EK for its delivery phase, instead spreading via the exploitation of the SMB protocol [3]. The malware would leverage the compromised systems as hosts for the PurpleFox payloads to facilitate its spread to other systems. This mode of infection can occur without any user action, akin to a worm.
The current iteration of PurpleFox reportedly uses brute-forcing of vulnerable services, such as SMB, to facilitate its spread over the network and escalate privileges. By scanning internet-facing Windows computers, PurpleFox exploits weak passwords for Windows user accounts through SMB, including administrative credentials to facilitate further privilege escalation.
Darktrace detection of PurpleFox
In July 2023, Darktrace observed an example of a PurpleFox infection on the network of a customer in the healthcare sector. This observation was a slightly different method of downloading the PurpleFox payload. An affected device was observed initiating a series of service control requests using DCE-RPC, instructing the device to make connections to a host of servers to download a malicious .PNG file, later confirmed to be the PurpleFox rootkit. The device was then observed carrying out worm-like activity to other external internet-facing servers, as well as scanning related subnets.
Darktrace DETECT™ was able to successfully identify and track this compromise across the cyber kill chain and ensure the customer was able to take swift remedial action to prevent the attack from escalating further.
While the customer in question did have Darktrace RESPOND™, it was configured in human confirmation mode, meaning any mitigative actions had to be manually applied by the customer’s security team. If RESPOND had been enabled in autonomous response mode at the time of the attack, it would have been able to take swift action against the compromise to contain it at the earliest instance.
Attack Overview
Initial Scanning over SMB
On July 14, 2023, Darktrace detected the affected device scanning other internal devices on the customer’s network via port 445. The numerous connections were consistent with the aforementioned worm-like activity that has been reported from PurpleFox behavior as it appears to be targeting SMB services looking for open or vulnerable channels to exploit.
This initial scanning activity was detected by Darktrace DETECT, specifically through the model breach ‘Device / Suspicious SMB Scanning Activity’. Darktrace’s Cyber AI Analyst™ then launched an autonomous investigation into these internal connections and tied them into one larger-scale network reconnaissance incident, rather than a series of isolated connections.
As Darktrace RESPOND was configured in human confirmation mode, it was unable to autonomously block these internal connections. However, it did suggest blocking connections on port 445, which could have been manually applied by the customer’s security team.
Privilege Escalation
The device successfully logged in via NTLM with the credential, ‘administrator’. Darktrace recognized that the endpoint was external to the customer’s environment, indicating that the affected device was now being used to propagate the malware to other networks. Considering the lack of observed brute-force activity up to this point, the credentials for ‘administrator’ had likely been compromised prior to Darktrace’s deployment on the network, or outside of Darktrace’s purview via a phishing attack.
Exploitation
Darktrace then detected a series of service control requests over DCE-RPC using the credential ‘admin’ to make SVCCTL Create Service W Requests. A script was then observed where the controlled device is instructed to launch mshta.exe, a Windows-native binary designed to execute Microsoft HTML Application (HTA) files. This enables the execution of arbitrary script code, VBScript in this case.
There are a few MSIEXEC flags to note:
- /i : installs or configures a product
- /Q : sets the user interface level. In this case, it is set to ‘No UI’, which is used for “quiet” execution, so no user interaction is required
Evidently, this was an attempt to evade detection by endpoint users as it is surreptitiously installed onto the system. This corresponds to the download of the rootkit that has previously been associated with PurpleFox. At this stage, the infected device continues to be leveraged as an attack device and scans SMB services over external endpoints. The device also appeared to attempt brute-forcing over NTLM using the same ‘administrator’ credential to these endpoints. This activity was identified by Darktrace DETECT which, if enabled in autonomous response mode would have instantly blocked similar outbound connections, thus preventing the spread of PurpleFox.
Installation
On August 9, Darktrace observed the device making initial attempts to download a malicious .PNG file. This was a notable change in tactics from previously reported PurpleFox campaigns which had been observed utilizing .MOE files for their payloads [3]. The .MOE payloads are binary files that are more easily detected and blocked by traditional signatured-based security measures as they are not associated with known software. The ubiquity of .PNG files, especially on the web, make identifying and blacklisting the files significantly more difficult.
The first connection was made with the URI ‘/test.png’. It was noted that the HTTP method here was HEAD, a method similar to GET requests except the server must not return a message-body in the response.
The metainformation contained in the HTTP headers in response to a HEAD request should be identical to the information sent in response to a GET request. This method is often used to test hypertext links for validity and recent modification. This is likely a way of checking if the server hosting the payload is still active. Avoiding connections that could possibly be detected by antivirus solutions can help keep this activity under-the-radar.
The server responds with a status code of 200 before the download begins. The HEAD request could be part of the attacker’s verification that the server is still running, and that the payload is available for download. The ‘/test.png’ HEAD request was sent twice, likely for double confirmation to begin the file transfer.
Subsequent analysis using a Packet Capture (PCAP) tool revealed that this connection used the Windows Installer user agent that has previously been associated with PurpleFox. The device then began to download a payload that was masquerading as a Microsoft Word document. The device was thus able to download the payload twice, from two separate endpoints.
By masquerading as a Microsoft Word file, the threat actor was likely attempting to evade the detection of the endpoint user and traditional security tools by passing off as an innocuous text document. Likewise, using a Windows Installer user agent would enable threat actors to bypass antivirus measures and disguise the malicious installation as legitimate download activity.
Darktrace DETECT identified that these were masqueraded file downloads by correctly identifying the mismatch between the file extension and the true file type. Subsequently, AI Analyst was able to correctly identify the file type and deduced that this download was indicative of the device having been compromised.
In this case, the device attempted to download the payload from several different endpoints, many of which had low antivirus detection rates or open-source intelligence (OSINT) flags, highlighting the need to move beyond traditional signature-base detections.
If Darktrace RESPOND was enabled in autonomous response mode at the time of the attack it would have acted by blocking connections to these suspicious endpoints, thus preventing the download of malicious files. However, as RESPOND was in human confirmation mode, RESPOND actions required manual application by the customer’s security team which unfortunately did not happen, as such the device was able to download the payloads.
Schlussfolgerung
The PurpleFox malware is a particularly dynamic strain known to continually evolve over time, utilizing a blend of old and new approaches to achieve its goals which is likely to muddy expectations on its behavior. By frequently employing new methods of attack, malicious actors are able to bypass traditional security tools that rely on signature-based detections and static lists of indicators of compromise (IoCs), necessitating a more sophisticated approach to threat detection.
Darktrace DETECT’s Self-Learning AI enables it to confront adaptable and elusive threats like PurpleFox. By learning and understanding customer networks, it is able to discern normal network behavior and patterns of life, distinguishing expected activity from potential deviations. This anomaly-based approach to threat detection allows Darktrace to detect cyber threats as soon as they emerge.
By combining DETECT with the autonomous response capabilities of RESPOND, Darktrace customers are able to effectively safeguard their digital environments and ensure that emerging threats can be identified and shut down at the earliest stage of the kill chain, regardless of the tactics employed by would-be attackers.
Credit to Piramol Krishnan, Cyber Analyst, Qing Hong Kwa, Senior Cyber Analyst & Deputy Team Lead, Singapore
Appendices
Darktrace Model Detections
- Device / Increased External Connectivity
- Device / Large Number of Connections to New Endpoints
- Device / SMB Session Brute Force (Admin)
- Compliance / External Windows Communications
- Anomalous Connection / New or Uncommon Service Control
- Compromise / Unusual SVCCTL Activity
- Compromise / Rare Domain Pointing to Internal IP
- Anomalous File / Masqueraded File Transfer
RESPOND Models
- Antigena / Network / Significant Anomaly / Antigena Breaches Over Time Block
- Antigena / Network / External Threat / Antigena Suspicious Activity Block
- Antigena / Network / Significant Anomaly / Antigena Significant Anomaly from Client Block
- Antigena / Network / Significant Anomaly / Antigena Enhanced Monitoring from Client Block
- Antigena / Network / External Threat / Antigena Suspicious File Block
- Antigena / Network / External Threat / Antigena File then New Outbound Block
List of IoCs
IoC - Type - Description
/C558B828.Png - URI - URI for Purple Fox Rootkit [4]
5b1de649f2bc4eb08f1d83f7ea052de5b8fe141f - File Hash - SHA1 hash of C558B828.Png file (Malware payload)
190.4.210[.]242 - IP - Purple Fox C2 Servers
218.4.170[.]236 - IP - IP for download of .PNG file (Malware payload)
180.169.1[.]220 - IP - IP for download of .PNG file (Malware payload)
103.94.108[.]114:10837 - IP - IP from Service Control MSIEXEC script to download PNG file (Malware payload)
221.199.171[.]174:16543 - IP - IP from Service Control MSIEXEC script to download PNG file (Malware payload)
61.222.155[.]49:14098 - IP - IP from Service Control MSIEXEC script to download PNG file (Malware payload)
178.128.103[.]246:17880 - IP - IP from Service Control MSIEXEC script to download PNG file (Malware payload)
222.134.99[.]132:12539 - IP - IP from Service Control MSIEXEC script to download PNG file (Malware payload)
164.90.152[.]252:18075 - IP - IP from Service Control MSIEXEC script to download PNG file (Malware payload)
198.199.80[.]121:11490 - IP - IP from Service Control MSIEXEC script to download PNG file (Malware payload)
MITRE ATT&CK Mapping
Tactic - Technique
Reconnaissance - Active Scanning T1595, Active Scanning: Scanning IP Blocks T1595.001, Active Scanning: Vulnerability Scanning T1595.002
Resource Development - Obtain Capabilities: Malware T1588.001
Initial Access, Defense Evasion, Persistence, Privilege Escalation - Valid Accounts: Default Accounts T1078.001
Initial Access - Drive-by Compromise T1189
Defense Evasion - Masquerading T1036
Credential Access - Brute Force T1110
Discovery - Network Service Discovery T1046
Command and Control - Proxy: External Proxy T1090.002
References
- https://blog.360totalsecurity.com/en/purple-fox-trojan-burst-out-globally-and-infected-more-than-30000-users/
- https://www.trendmicro.com/en_us/research/19/i/purple-fox-fileless-malware-with-rookit-component-delivered-by-rig-exploit-kit-now-abuses-powershell.html
- https://www.akamai.com/blog/security/purple-fox-rootkit-now-propagates-as-a-worm
- https://www.foregenix.com/blog/an-overview-on-purple-fox
- https://www.trendmicro.com/en_sg/research/21/j/purplefox-adds-new-backdoor-that-uses-websockets.html
Blog
OT
$70 Million in Cyber Security Funding for Electric Cooperatives & Utilities
What is the Bipartisan Infrastructure Deal?
The Bipartisan Infrastructure Law passed by congress in 2021 aimed to upgrade power and infrastructure to deliver clean, reliable energy across the US to achieve zero-emissions. To date, the largest investment in clean energy, the deal will fund new programs to support the development and deployment of clean energy technology.
Why is it relevant to electric municipalities?
Section 40124 of the Bipartisan Infrastructure Law allocates $250 million over a 5-year period to create the Rural and Municipal Utility Cybersecurity (RMUC) Program to help electric cooperative, municipal, and small investor-owned utilities protect against, detect, respond to, and recover from cybersecurity threats.1 This act illuminates the value behind a full life-cycle approach to cyber security. Thus, finding a cyber security solution that can provide all aspects of security in one integrated platform would enhance the overall security posture and ease many of the challenges that arise with adopting multiple point solutions.
On November 16, 2023 the Office of Cybersecurity, Energy Security, and Emergency Response (CESER) released the Advanced Cybersecurity Technology (ACT) for electric utilities offering a $70 million funding opportunity that aims to enhance the cybersecurity posture of electric cooperative, municipal, and small investor-owned utilities.
Funding Details
10 projects will be funded with application submissions due November 29, 2023, 5:00 pm ET with $200,000 each in cash prizes in the following areas:
- Direct support for eligible utilities to make investments in cybersecurity technologies, tools, training, and improvements in utility processes and procedures;
- Funding to strengthen the peer-to-peer and not-for-profit cybersecurity technical assistance ecosystem currently serving eligible electric utilities; and
- Increasing access to cybersecurity technical assistance and training for eligible utilities with limited cybersecurity resources. 2
To submit for this award visit: https://www.herox.com/ACT1Prize
How can electric municipalities utilize the funding?
While the adoption of hybrid working patterns increase cloud and SaaS usage, the number of industrial IoT devices also continues to rise. The result is decrease in visibility for security teams and new entry points for attackers. Particularly for energy and utility organizations.
Electric cooperatives seeking to enhance their cyber security posture can aim to invest in cyber security tools that provide the following:
Compliance support: Consider finding an OT security solution that maps out how its solutions and features help your organization comply with relevant compliance mandates such as NIST, ISA, FERC, TSA, HIPAA, CIS Controls, and more.
Anomaly based detection: Siloed security solutions also fail to detect attacks that span
the entire organization. Anomaly-based detection enhances an organization’s cyber security posture by proactively defending against potential attacks and maintaining a comprehensive view of their attack surface.
Integration capabilities: Implementation of several point solutions that complete individual tasks runs the risk of increasing workloads for operators and creates additional challenges with compliance, budgeting, and technical support. Look for cyber security tools that integrate with your existing technologies.
Passive and active asset tracking: Active Identification offers accurate enumeration, real time updates, vulnerability assessment, asset validation while Passive Identification eliminates the risk of operational disruption, minimizes risk, does not generate additional network traffic. It would be ideal to find a security solution that can do both.
Can secure both IT and OT in unison: Given that most OT cyber-attacks actually start in IT networks before pivoting into OT, a mature security posture for critical infrastructure would include a single solution for both IT and OT. Separate solutions for IT and OT present challenges when defending network boundaries and detecting incidents when an attacker pivots from IT to OT. These independent solutions also significantly increase operator workload and materially diminish risk mitigation efforts.
Darktrace/OT for Electric Cooperatives and Utilities
For smaller teams with just one or two dedicated employees, Darktrace’s Cyber AI Analyst and Investigation features allow end users to spend less time in the platform as it compiles critical incidents into comprehensive actionable event reports. AI Analyst brings all the information into a centralized view with incident reporting in natural language summaries and can be generated for compliance reports specific to regulatory requirements.
For larger teams, Darktrace alerts can be forwarded to 3rd party platforms such as a SIEM, where security team decision making is augmented. Additionally, executive reports and autonomous response reduce the alert fatigue generally associated with legacy tools. Most importantly, Darktrace’s unique understanding of normal allows security teams to detect zero-days and signatureless attacks regardless of the size of the organization and how alerts are consumed.
Key Benefits of Darktrace/OT
- Anomaly-based detection and real-time response
- Secures IT, OT, and IoT in unison
- Active and Passive Asset Identification
- Automated security reporting
- Attack surface management and vulnerability assessment
- Covers all levels of the Purdue Model
.png)
References
