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A l'intérieur du SOC
Comment l'IA a découvert l'opération secrète d'extraction de crypto-monnaies d'Outlaw.
Infamy is a paradoxical calling for cyber-criminals. While for some, bragging rights are a motivation for cyber-crime in and of themselves, notoriety is usually not a sensible goal for those hoping to avoid detection. This is what threat actors behind the prolific Emotet botnet learned earlier in 2021, for instance, when a coordinated effort was launched by eight national law enforcement agencies to take down their operation. There are, however, certain names which appear again and again in cyber security media and consistently avoid detection – names like Outlaw.
How Outlaw plans an ambush
Despite being active since 2018, very little is known about the hacking group Outlaw, which has staged numerous botnet and crypto-jacking attacks in China and internationally. The group is recognized by a variety of calling cards, be they repeated filenames or a tendency to illicitly mine Monero cryptocurrency, but its success ultimately lies in its tendency to adapt and evolve during months of dormancy between attacks.
Outlaw’s attacks are marked by constant changes and updates, which they work on in relative silence, before targeting security systems which are too-often defeated by the unfamiliarity of the threat.
In 2020, Outlaw gained attention when they updated their botnet toolset to find and eradicate other criminals’ crypto-jacking software, maximizing their own payout from infected devices. While it might come as no surprise that there’s no honor among cyber-thieves, this update also implemented more troubling changes which allowed Outlaw’s malware to evade traditional security defenses.
By switching disguises between each big robbery, and laying low with the loot, Outlaw ensures that traditional security systems which rely on historical attack data will never be ready for them, no matter how much notoriety is attached to their name. When organizations move beyond these systems’ rules-based approaches, however, adopting Self-Learning AI to protect their digital estates, they can begin to turn the tables on groups like Outlaw.
This blog explores how two pre-infected zombie devices in two very different parts of the world were activated by Outlaw’s botnet in the summer of 2021, and how Darktrace was able to detect the activity despite the devices being pre-infected.
Bounty hunting: First signs of attack
Figure 1: Timeline of the attack.
When a new device was added to the network of a Central American telecomms company in July, Darktrace detected a series of regular connections to two suspicious endpoints which it identified as beaconing behavior. The same behavior was noticed independently, but almost simultaneously, at a financial company in the APAC region, which was implementing Darktrace for the first time. Darktrace’s Self-Learning AI was able to identify the pre-infected devices by clustering similarly-behaving devices into peer groups within the local digital estates and therefore recognize that both were acting unusually based on a range of behaviors.
The first sign that the zombie devices had been activated by Outlaw was the initiation of cryptocurrency mining. Both devices, despite their geographical distance, were discovered to be connected to a single crypto-account, exemplifying the indiscriminate and exponential nature by which a botnet grows.
Outlaw has in the past restricted its activities to devices within China in what was assumed to be a show of caution, but recent activities like this one speak to a growing confidence.
The botnet recruitment process
The subsequent initiation of Internet Relay Chat (IRC) connections across port 443, a port more often associated with HTTPS activity, was perfectly characteristic of the Outlaw botnet’s earlier activity in 2020. IRC is a tool regularly used for communication between botmasters and zombie devices, but by using port 443 the attacker was attempting to blend into normal Internet traffic.
Soon after this exchange, the devices downloaded a shell script. Darktrace’s Cyber AI Analyst was able to intercept and recreate this shell script as it passed through the network, revealing its full function. Intriguingly, the script identified and excluded devices utilizing ARM architecture from the botnet. Due to its notably low battery consumption, ARM architecture is used primarily by portable mobile devices.
This selectivity is evidence that malicious crypto-mining remains Outlaw’s primary objective. By circumventing smaller devices which offer limited crypto-mining capabilities, this shell script focuses the botnet on the most high-powered, and therefore profitable, devices, such as desktop computers and servers. In this way, it reduces the Indicators of Compromise (IOCs) left behind by the wider botnet without greatly affecting the scale of its crypto-mining operation.
The two devices in question did not employ ARM architecture, and minutes later received a secondary payload containing a file named dota3[.]tar[.]gz, a sequel of sorts to the previous incarnation of the Outlaw botnet, ‘dota2’, which itself referenced a popular video game of the same name. With the arrival of this file, the devices appear to have been updated with the latest version of Outlaw’s world-spanning botnet.
This download was made possible in part by the attacker’s use of ‘Living off the Land’ tactics. By using only common Linux programs already present on the devices (‘curl’ and ‘Wget’ respectively), Outlaw had avoided having its activity flagged by traditional security systems. Wget, for instance, is ostensibly a reputable program used for retrieving content from web servers, and was never previously recorded as part of Outlaw’s TTPs (Tactics, Techniques, and Procedures).
By evolving and adapting its approach, Outlaw is continually able to outsmart and outrun rules-based security. Darktrace’s Self-Learning AI, however, kept pace, immediately identifying this Wget connection as suspicious and advising further investigation.
Figure 2: Cyber AI Analyst identifies Wget use on the morning of July 15 as suspicious and begins investigating potentially related HTTP connections made on the morning of July 14. In this way, it builds a complete picture of the attack.
The botnet unchained
In the following 36 hours, Darktrace detected over 6 million TCP and SSH connections directed to rare external IP addresses using ports often associated with SSH, such as 22, 2222, and 2022.
Exactly what the botnet was undertaking with these connections can only be speculated on. The devices may have been made part of a DDoS (Distributed Denial of Service) attack, bruteforce attempts on targeted SSH accounts, or simply have taken up the task of seeking and infecting new targets, further expanding the botnet. Darktrace recognized that neither device had made SSH connections prior to this event and, had Antigena been in active mode, would have enacted measures to stop them.
Figure 3: The behavior on the device before and after the bot was activated on July 14, 2021. The large spike in model breaches shows clear deviation from the established ‘pattern of life’.
Thankfully, the owners of both devices responded to Darktrace’s detection alerts soon enough to prevent any serious damage to their own digital estates. Had these devices remained under the influence of the botnet, the ramifications may have been far graver.
The use of SSH protocol would have allowed Outlaw to pivot into any number of activities, potentially compromising each device’s network further and causing data or monetary loss to their respective organizations.
Call the sheriff: Self-Learning AI
Rules-based security solutions operate much like the ‘wanted’ posters of the old west, looking out for the criminals who came through town last week without preparing for those riding over the hill today. When black hats and outlaws are adopting new looks and employing new techniques with every attack, a new way of responding to threats is needed.
Darktrace doesn’t need to know the name ‘Outlaw’, or the group’s history of evolving attacks, in order to stop them. With its fundamental self-learning approach, Darktrace learns its surroundings from the ground up, and identifies subtle deviations indicative of a cyber-threat. And with Autonomous Response, it will even take targeted action to neutralize the threat at machine speed, without the need for human intervention.
Thanks to Darktrace analyst Jun Qi Wong for his insights on the above threat find.
Learn more about how Cyber AI Analyst sheds light on complex attacks
Technical details
Darktrace model detections
- Compliance / Crypto Currency Mining Activity
- Compromise / High Priority Crypto Currency Mining [Enhanced Monitoring]
- Anomalous Connection / New User Agent to IP Without Hostname
- Anomalous File / Zip or Gzip from Rare External Location
- Anomalous Connection / Application Protocol on Uncommon Port
- Device / Increased External Connectivity
- Unusual Activity / Unusual External Activity
- Compromise / SSH Beacon
- Compromise / High Frequency SSH Beacon
- Anomalous Connection / Multiple Connections to New External TCP Port
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A l'intérieur du SOC
Protecting Prospects: How Darktrace Detected an Account Hijack Within Days of Deployment
Cloud Migration Expanding the Attack Surface
Cloud migration is here to stay – accelerated by pandemic lockdowns, there has been an ongoing increase in the use of public cloud services, and Gartner has forecasted worldwide public cloud spending to grow around 20%, or by almost USD 600 billion [1], in 2023. With more and more organizations utilizing cloud services and moving their operations to the cloud, there has also been a corresponding shift in malicious activity targeting cloud-based software and services, including Microsoft 365, a prominent and oft-used Software-as-a-Service (SaaS).
With the adoption and implementation of more SaaS products, the overall attack surface of an organization increases – this gives malicious actors additional opportunities to exploit and compromise a network, necessitating proper controls to be in place. This increased attack surface can leave organization’s open to cyber risks like cloud misconfigurations, supply chain attacks and zero-day vulnerabilities [2]. In order to achieve full visibility over cloud activity and prevent SaaS compromise, it is paramount for security teams to deploy sophisticated security measures that are able to learn an organization’s SaaS environment and detect suspicious activity at the earliest stage.
Darktrace Immediately Detects Hijacked Account
In May 2023, Darktrace observed a chain of suspicious SaaS activity on the network of a customer who was about to begin their trial of Darktrace/Cloud™ and Darktrace/Email™. Despite being deployed on the network for less than a week, Darktrace DETECT™ recognized that the legitimate SaaS account, belonging to an executive at the organization, had been hijacked. Darktrace/Email was able to provide full visibility over inbound and outbound mail and identified that the compromised account was subsequently used to launch an internal spear-phishing campaign.
If Darktrace RESPOND™ were enabled in autonomous response mode at the time of this compromise, it would have been able to take swift preventative action to disrupt the account compromise and prevent the ensuing phishing attack.
Account Hijack Attack Overview
Unusual External Sources for SaaS Credentials
On May 9, 2023, Darktrace DETECT/Cloud detected the first in a series of anomalous activities performed by a Microsoft 365 user account that was indicative of compromise, namely a failed login from an external IP address located in Virginia.
Just a few minutes later, Darktrace observed the same user credential being used to successfully login from the same unusual IP address, with multi-factor authentication (MFA) requirements satisfied.
A few hours after this, the user credential was once again used to login from a different city in the state of Virginia, with MFA requirements successfully met again. Around the time of this activity, the SaaS user account was also observed previewing various business-related files hosted on Microsoft SharePoint, behavior that, taken in isolation, did not appear to be out of the ordinary and could have represented legitimate activity.
The following day, May 10, however, there were additional login attempts observed from two different states within the US, namely Texas and Florida. Darktrace understood that this activity was extremely suspicious, as it was highly improbable that the legitimate user would be able to travel over 2,500 miles in such a short period of time. Both login attempts were successful and passed MFA requirements, suggesting that the malicious actor was employing techniques to bypass MFA. Such MFA bypass techniques could include inserting malicious infrastructure between the user and the application and intercepting user credentials and tokens, or by compromising browser cookies to bypass authentication controls [3]. There have also been high-profile cases in the recent years of legitimate users mistakenly (and perhaps even instinctively) accepting MFA prompts on their token or mobile device, believing it to be a legitimate process despite not having performed the login themselves.
New Email Rule
On the evening of May 10, following the successful logins from multiple US states, Darktrace observed the Microsoft 365 user creating a new inbox rule, named “.’, in Microsoft Outlook from an IP located in Florida. Threat actors are often observed naming new email rules with single characters, likely to evade detection, but also for the sake of expediency so as to not expend any additional time creating meaningful labels.
In this case the newly created email rules included several suspicious properties, including ‘AlwaysDeleteOutlookRulesBlob’, ‘StopProcessingRules’ and “MoveToFolder”.
Firstly, ‘AlwaysDeleteOutlookRulesBlob’ suppresses or hides warning messages that typically appear if modifications to email rules are made [4]. In this case, it is likely the malicious actor was attempting to implement this property to obfuscate the creation of new email rules.
The ‘StopProcessingRules’ rule meant that any subsequent email rules created by the legitimate user would be overridden by the email rule created by the malicious actor [5]. Finally, the implementation of “MoveToFolder” would allow the malicious actor to automatically move all outgoing emails from the “Sent” folder to the “Deleted Items” folder, for example, further obfuscating their malicious activities [6]. The utilization of these email rule properties is frequently observed during account hijackings as it allows attackers to delete and/or forward key emails, delete evidence of exploitation and launch phishing campaigns [7].
In this incident, the new email rule would likely have enabled the malicious actor to evade the detection of traditional security measures and achieve greater persistence using the Microsoft 365 account.
Account Update
A few hours after the creation of the new email rule, Darktrace observed the threat actor successfully changing the Microsoft 365 user’s account password, this time from a new IP address in Texas. As a result of this action, the attacker would have locked out the legitimate user, effectively gaining full access over the SaaS account.
Phishing Emails
The compromised SaaS account was then observed sending a high volume of suspicious emails to both internal and external email addresses. Darktrace was able to identify that the emails attempting to impersonate the legitimate service DocuSign and contained a malicious link prompting users to click on the text “Review Document”. Upon clicking this link, users would be redirected to a site hosted on Adobe Express, namely hxxps://express.adobe[.]com/page/A9ZKVObdXhN4p/.
Adobe Express is a free service that allows users to create web pages which can be hosted and shared publicly; it is likely that the threat actor here leveraged the service to use in their phishing campaign. When clicked, such links could result in a device unwittingly downloading malware hosted on the site, or direct unsuspecting users to a spoofed login page attempting to harvest user credentials by imitating legitimate companies like Microsoft.
The malicious site hosted on Adobe Express was subsequently taken down by Adobe, possibly in response to user reports of maliciousness. Unfortunately though, platforms like this that offer free webhosting services can easily and repeatedly be abused by malicious actors. Simply by creating new pages hosted on different IP addresses, actors are able to continue to carry out such phishing attacks against unsuspecting users.
In addition to the suspicious SaaS and email activity that took place between May 9 and May 10, Darktrace/Email also detected the compromised account sending and receiving suspicious emails starting on May 4, just two days after Darktrace’s initial deployment on the customer’s environment. It is probable that the SaaS account was compromised around this time, or even prior to Darktrace’s deployment on May 2, likely via a phishing and credential harvesting campaign similar to the one detailed above.
Darktrace Coverage
As the customer was soon to begin their trial period, Darktrace RESPOND was set in “human confirmation” mode, meaning that any preventative RESPOND actions required manual application by the customer’s security team.
If Darktrace RESPOND had been enabled in autonomous response mode during this incident, it would have taken swift mitigative action by logging the suspicious user out of the SaaS account and disabling the account for a defined period of time, in doing so disrupting the attack at the earliest possible stage and giving the customer the necessary time to perform remediation steps. As it was, however, these RESPOND actions were suggested to the customer’s security team for them to manually apply.
Nevertheless, with Darktrace DETECT/Cloud in place, visibility over the anomalous cloud-based activities was significantly increased, enabling the swift identification of the chain of suspicious activities involved in this compromise.
In this case, the prospective customer reached out to Darktrace directly through the Ask the Expert (ATE) service. Darktrace’s expert analyst team then conducted a timely and comprehensive investigation into the suspicious activity surrounding this SaaS compromise, and shared these findings with the customer’s security team.
Conclusion
Ultimately, this example of SaaS account compromise highlights Darktrace’s unique ability to learn an organization’s digital environment and recognize activity that is deemed to be unexpected, within a matter of days.
Due to the lack of obvious or known indicators of compromise (IoCs) associated with the malicious activity in this incident, this account hijack would likely have gone unnoticed by traditional security tools that rely on a rules and signatures-based approach to threat detection. However, Darktrace’s Self-Learning AI enables it to detect the subtle deviations in a device’s behavior that could be indicative of an ongoing compromise.
Despite being newly deployed on a prospective customer’s network, Darktrace DETECT was able to identify unusual login attempts from geographically improbable locations, suspicious email rule updates, password changes, as well as the subsequent mounting of a phishing campaign, all before the customer’s trial of Darktrace had even begun.
When enabled in autonomous response mode, Darktrace RESPOND would be able to take swift preventative action against such activity as soon as it is detected, effectively shutting down the compromise and mitigating any subsequent phishing attacks.
With the full deployment of Darktrace’s suite of products, including Darktrace/Cloud and Darktrace/Email, customers can rest assured their critical data and systems are protected, even in the case of hybrid and multi-cloud environments.
Credit: Samuel Wee, Senior Analyst Consultant & Model Developer
Appendices
References
[2] https://www.upguard.com/blog/saas-security-risks
[4] https://learn.microsoft.com/en-us/powershell/module/exchange/disable-inboxrule?view=exchange-ps
[7] https://blog.knowbe4.com/check-your-email-rules-for-maliciousness
Darktrace Model Detections
Darktrace DETECT/Cloud and RESPOND Models Breached:
SaaS / Access / Unusual External Source for SaaS Credential Use
SaaS / Unusual Activity / Multiple Unusual External Sources for SaaS Credential
Antigena / SaaS / Antigena Unusual Activity Block (RESPOND Model)
SaaS / Compliance / New Email Rule
Antigena / SaaS / Antigena Significant Compliance Activity Block
SaaS / Compromise / Unusual Login and New Email Rule (Enhanced Monitoring Model)
Antigena / SaaS / Antigena Suspicious SaaS Activity Block (RESPOND Model)
SaaS / Compromise / SaaS Anomaly Following Anomalous Login (Enhanced Monitoring Model)
SaaS / Compromise / Unusual Login and Account Update
Antigena / SaaS / Antigena Suspicious SaaS Activity Block (RESPOND Model)
IoC – Type – Description & Confidence
hxxps://express.adobe[.]com/page/A9ZKVObdXhN4p/ - Domain – Probable Phishing Page (Now Defunct)
37.19.221[.]142 – IP Address – Unusual Login Source
35.174.4[.]92 – IP Address – Unusual Login Source
MITRE ATT&CK Mapping
Tactic - Techniques
INITIAL ACCESS, PRIVILEGE ESCALATION, DEFENSE EVASION, PERSISTENCE
T1078.004 – Cloud Accounts
DISCOVERY
T1538 – Cloud Service Dashboards
CREDENTIAL ACCESS
T1539 – Steal Web Session Cookie
RESOURCE DEVELOPMENT
T1586 – Compromise Accounts
PERSISTENCE
T1137.005 – Outlook Rules
Blog
Darktrace/Email in Action: Why AI-Driven Email Security is the Best Defense Against Sustained Phishing Campaigns
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Stopping the bad while allowing the good
Since its inception, email has been regarded as one of the most important tools for businesses, revolutionizing communication and allowing global teams to become even more connected. But besides organizations heavily relying on email for their daily operations, threat actors have also recognized that the inbox is one of the easiest ways to establish an initial foothold on the network.
Today, not only are phishing campaigns and social engineering attacks becoming more prevalent, but the level of sophistication of these attacks are also increasing with the help of generative AI tools that allow for the creation of hyper-realistic emails with minimal errors, effectively lowering the barrier to entry for threat actors. These diverse and stealthy types of attacks evade traditional email security tools based on rules and signatures, because they are less likely to contain the low-sophistication markers of a typical phishing attack.
In a situation where the sky is the limit for attackers and security teams are lean, how can teams equip themselves to tackle these threats? How can they accurately detect increasingly realistic malicious emails and neutralize these threats before it is too late? And importantly, how can email security block these threats while allowing legitimate emails to flow freely?
Instead of relying on past attack data, Darktrace’s Self-Learning AI detects the slightest deviation from a user’s pattern of life and responds autonomously to contain potential threats, stopping novel attacks in their tracks before damage is caused. It doesn’t define ‘good’ and ‘bad’ like traditional email tools, rather it understands each user and what is normal for them – and what’s not.
This blog outlines how Darktrace/Email™ used its understanding of ‘normal’ to accurately detect and respond to a sustained phishing campaign targeting a real-life company.
Responding to a sustained phishing attack
Over the course of 24 hours, Darktrace detected multiple emails containing different subjects, all from different senders to different recipients in one organization. These emails were sent from different IP addresses, but all came from the same autonomous system number (ASN).
The emails themselves had many suspicious indicators. All senders had no prior association with the recipient, and the emails generated a high general inducement score. This score is generated by structural and non-specific content analysis of the email – a high score indicates that the email is trying to induce the recipient into taking a particular action, which may lead to account compromise.
Additionally, each email contained a visually prominent link to a file storage service, hidden behind a shortened bit.ly link. The similarities across all these emails pointed to a sustained campaign targeting the organization by a single threat actor.
With all these suspicious indicators, many models were breached. This drove up the anomaly score, causing Darktrace/Email to hold all suspicious emails from the recipients’ inboxes, safeguarding the recipients from potential account compromise and disallowing the threats from taking hold in the network.
Imagining a phishing attack without Darktrace/Email
So what could have happened if Darktrace had not withheld these emails, and the recipients had clicked on the links? File storage sites have a wide variety of uses that allow attackers to be creative in their attack strategy. If the user had clicked on the shortened link, the possible consequences are numerous. The link could have led to a login page for unsuspecting victims to input their credentials, or it could have hosted malware that would automatically download if the link was clicked. With the compromised credentials, threat actors could even bypass MFA, change email rules, or gain privileged access to a network. The downloaded malware might also be a keylogger, leading to cryptojacking, or could open a back door for threat actors to return to at a later time.
The limits of traditional email security tools
Secure email gateways (SEGs) and static AI security tools may have found it challenging to detect this phishing campaign as malicious. While Darktrace was able to correlate these emails to determine that a sustained phishing campaign was taking place, the pattern among these emails is far too generic for specific rules as set in traditional security tools. If we take the characteristic of the freemail account sender as an example, setting a rule to block all emails from freemail accounts may lead to more legitimate emails being withheld, since these addresses have a variety of uses.
With these factors in mind, these emails could have easily slipped through traditional security filters and led to a devastating impact on the organization.
Conclusion
As threat actors step up their attacks in sophistication, prioritizing email security is more crucial than ever to preserving a safe digital environment. In response to these challenges, Darktrace/Email offers a set-and-forget solution that continuously learns and adapts to changes in the organization.
Through an evolving understanding of every environment in which it is deployed, its threat response becomes increasingly precise in neutralizing only the bad, while allowing the good – delivering email security that doesn’t come at the expense of business growth.