Ransomware protection and incident response is a constant battle for IT, security engineers and analysts under normal circumstances, but with the number of people working from home during the COVID-19 pandemic that challenge reaches new heights. How do you ensure an equivalent level of adaptable malware protection on or off the corporate network? How do you enable remote services securely? How long will it take you to recover remote end user systems and data encrypted by ransomware?
As remote workers and IT engineers increasingly use Remote Desktop Protocol (RDP) to access internal resources, attackers are finding more weaknesses to exploit. Attackers are exploiting weak authentication or security controls and even resorting to buying RDP passwords in the underground markets. Exploiting these weaknesses can give an attacker admin access and an easy path to install ransomware or other types of malware, then find their way around the corporate network. To see some examples of how attackers are exploiting RDP weaknesses, check out additional blog posts from McAfee Advanced Threat Research (ATR)
- Organizations Leave Backdoors Open to Cheap Remote Desktop Protocol Attacks
- RDP Stands for “Really DO Patch!” – Understanding the Wormable RDP Vulnerability CVE-2019-0708
- Cybercriminals Actively Exploiting RDP to Target Remote Organizations
In this blog, we will show how you can leverage Endpoint Security or ENS, McAfee’s Endpoint Protection Platform (EPP), led by some of the new capabilities in ENS 10.7 and MVISION Endpoint Detection and Response (EDR), to do just that.
ENS 10.7, with Threat Prevention, Firewall, Web Control and Adaptive Threat Protection modules backed up by Global Threat Intelligence (GTI) provides adaptable, defense in depth capability against the techniques used in targeted ransomware attacks. For more examples of these techniques, see McAfee ATR’s recent blog on LockBit. Pairing ENS 10.7 with MVISION EDR gives the SOC analysts a powerful toolset to quickly identify attempts to steal credentials and lateral move further into the network.
Finally, McAfee ePolicy Orchestrator (ePO) provides a central management console for endpoint security policy, event collection and reporting on your protected systems on or off the corporate network. Let’s explore some of the key defensive steps you can take to lower your risk against targeted ransomware.
Prevent Initial Access with Threat Prevention
The Endpoint Security Threat Prevention module contains several capabilities including signature scanning and exploit prevention through behavior blocking and reputation analysis, to prevent an attacker gaining access to the system. The first step is to ensure you have the minimum level of security in place. This includes following best practice for on-access and on-demand scanning policies, up to date DAT Files and Engine, and Exploit Prevention content, as well as Global Threat Intelligence access enabled. Targeted ransomware attacks may also leverage file-less exploit techniques which could bypass file-based signature scans and reputation checks. Exploit Prevention rules can be configured to either log or block PowerShell behavior.
However, PowerShell is a legitimate system administration tool and we recommend a period of observation and testing before setting any of these rules to block. For some best practice, you can review this guide as a starting point or check with support for the latest documents.
Restrict RDP as an Initial Attack Vector with Endpoint Security Firewall
If RDP is needed to access internal resources on a server or to troubleshoot a remote system, the best practice is to restrict access to the service using a firewall. This will prevent attackers from leveraging RDP as the initial access vector. ENS 10.7 contains a stateful firewall fully managed via McAfee ePolicy Orchestrator (ePO). You can create policies to restrict RDP access to a remote client to only authorized IP addresses, restrict outbound usage to prevent lateral movement by RDP or block access to that port altogether. Here is an example configuration to restrict inbound access to a remote system on RDP.
- Open your Firewall Rules policy and locate the default rule under Network Tools.
- If you are using a non-standard port for RDP adjust the local port for this rule appropriately.
- Modify the rule by adding authorized IP addresses as remote networks (these are the remote addresses authorized to connect to your endpoints).
- Save the changes and apply the policy to endpoints to restrict RDP access.
For additional security create an identical rule but set to block rather than allow, position it below the above rule, and remove the remote IP addresses (so that it applies to all RDP connections not matching the above rule).
- Set this rule as an intrusion so that it logs all denied events and forwards them to ePO.
Security analysts in the SOC can then monitor and report on unauthorized access attempts through ePO dashboards. The event logs are useful for early warning, trend analysis and for threat detection and response.
You can find more information on Endpoint Security firewall features here.
Prevent Access to Malicious Websites with Web Control
Attackers often leverage watering holes and spear phishing with links to malicious sites to gain initial access or further infiltrate the network. When a user is on the corporate network, they are often behind a Web Proxy like McAfee Web Gateway. However, many of your mobile clients are going direct to the internet and not through the corporate VPN. This creates more exposure to web-based threats. The Endpoint Security Web Control module monitors web searching and browsing activity on client computers and protects against threats on webpages and in file downloads.
You use McAfee ePO to deploy and manage Web Control on client systems. Settings control access to sites based on their safety rating, reputation from Global Threat Intelligence, the type of content they contain, and their URL or domain name. The configuration settings allow you to adjust sensitivity to be more or less restrictive based on your risk appetite.
If you are a McAfee Web Gateway or Web Gateway Cloud Service customer, you should use McAfee Client Proxy (MCP). MCP works with Web Control to route traffic to the right proxy and provide a defense in depth capability for web protection for users on or off the corporate network.
The above are just a few examples of using Endpoint Security Threat Prevention, Web Control and Firewall to restrict initial attack vectors. To learn more about Endpoint Security best practice to restrict initial entry vectors, visit here.
Let’s look at a few more important steps to protect systems against targeted ransomware.
Lockdown the Security Crown Jewels
If an attacker gets on the system through RDP stolen accounts or vulnerability, they may try to modify, delete or disable security software. In ePO, you should ensure that Self Protection is ON to prevent McAfee services and files on the endpoint or server system from being stopped or modified.
Ensure that ENS is configured to require a password for uninstallation.
Security analysts should be on high alert for any system that has Self Protection disabled. ePO contains a default query entitled Endpoint Security: Self Protection Compliance Status which can be used to populate a continuous monitoring dashboard or be packaged into a daily report.
Disrupt and Visualize Attacker Behavior with Adaptive Threat Protection (ATP)
ATP adds several more capabilities, such as machine-learning, threat intelligence, script-scanning and application behavior analysis, to disrupt targeted attack techniques including file-based or file-less attacks.
For more information on how ATP remediates threats please review the product guide here.
One of the newest features of ENS 10.7 is the Story Graph. The Story Graph provides a visual representation of threat detections. Below is an example from a simulated file-less attack scenario where a Word document, delivered through spear-phishing, leverages a macro and PowerShell to provide command and control, then elevate privileges and perform lateral movement.
The visualization provides a timeline analysis and context around the event. It correctly captured the attack behavior including the communication to an external attacker IP address. With this visualization, an administrator or security analyst can quickly determine malicious behavior was stopped by ATP, preventing the follow-up activity intended by the attacker. The additional context, such as the originating process and a download IP address, can then be used for further investigations using other log sources, for example. It is important to note that in this example, if the Threat Prevention module as described above was set to block all PowerShell behavior, this attack would have been stopped earlier in the chain. Please read further to see what this attack scenario looks like in MVISION EDR.
For more information on how ATP protects against file-less attacks visit here.
Using a Word document and PowerShell is just one example of masquerading attacks in common files. For more examples of these techniques, see the ATR blog on LockBit ransomware.
ATP Brings Automatic File Recovery with Enhanced Remediation
If you have ever seen a ransom note, like the one from Wanna Decryptor below, you will know how big an issue it can be. It will cost you time, money and most likely lead to loss of data.
If this happens on a remote user system, it will lead to extended downtime, frustrated users and present significant challenges for recovery.
One of the new capabilities in ENS 10.7 is Enhanced Remediation. This feature monitors any process with an unknown reputation and backs up changes made by those processes. If the processes exhibit malicious behavior as determined by machine-learning analysis and reputation, enhanced remediation automatically rolls back those changes made to the system and documents to a previous state.
You can see how files impacted by ransomware can be restored through Enhanced Remediation in this video.
Enhanced Remediation requires that ATP is enabled and policies for Dynamic Application Containment are configured. Real Protect Dynamic scanning must also be enabled on the system. Real Protect Dynamic leverages machine learning in the cloud to identify suspicious behavior and is needed to determine a file reputation which is used to trigger an enhanced remediation action.
For information on how to configure ATP, please review the product guide here. For more best practices on tuning Dynamic Application Containment rules, please review the knowledge base article here.
Once policies are established, ensure that you enable “Enhanced Remediation” and “Monitor and remediate deleted and changed files”
If a file is convicted by Real Protect Dynamic and Enhanced Remediation is enabled with the settings above, then recovery happens automatically. The setting “Monitor and remediate deleted or changed files” must be enabled to ensure any files modified by the ransomware are restored to the previous state.
For more information on how Enhanced Remediation works, please review the product guide here.
Continuous Monitoring with ePO Protection Workspace
Now that you have protection controls in place with Threat Prevention and Adaptive Threat Protection, you can monitor using the Compliance Dashboard in ePO to ensure all managed clients stay up to date.
In addition, events triggered by ATP can be sent to ePO. SOC analysts should monitor these events and use the Story Graph as well for additional investigative capability. For more information on reporting and querying events in ePO, please review the product guide here.
Proactive Monitoring and Hunting with MVISION EDR
One of the first questions a threat hunter needs to answer when a new threat is discovered is “are we exposed?” For example, you may have a policy that already prohibits or restricts RDP but how do you know it is enforced on every endpoint? With MVISION EDR, you can perform a real time search across all managed systems to see what is happening right now. The screenshot below shows a Real-time Search to verify if RDP is enabled or disabled on a system. This provides a view into systems potentially at risk and can also be useful context as part of an investigation.
Real-time Search can also identify systems with active connections on RDP…
MVISION EDR also maintains a history of network connections inbound and outbound from the client. Performing an historical search for network traffic could identify systems that actively communicated on port 3389 to unauthorized addresses, potentially detecting attempts at exploitation.
For a security analyst, EDR providers several benefits to accelerate threat detection and response. For more information on those benefits please review the product guide here. In our simulated file-less attack scenario described above, the story graph revealed a PowerShell connection to an external IP address. Suppose an alert ePO administrator created a ticket for further investigation. A first step by the analyst might be a search for the network activity.
Real-time Search in EDR of that network activity looks like this…
An historical search for the same PowerShell activity in EDR now reveals the encoded commands used in the initial entry vector…
EDR also enables proactive monitoring by a security analyst. The Monitoring Dashboard helps the analyst in the SOC quickly triage suspicious behavior. In this case, the attack leveraged Word and PowerShell to gain access and raise privileges. The attack scenario triggered a number of high threats and provides a lot of context for the analyst to make a quick determination that an attack has been attempted, requiring further action…
Our research into targeted ransomware attacks reveals that if an attacker successfully exploits a client, their next actions involve privilege escalation and lateral movement (see our blog on LockBit). Again, you can use MVISION EDR to quickly detect these techniques.
The Alerting Dashboard in EDR will help you quickly identify attempts at privilege escalation and other attack techniques as defined by the MITRE ATT&CK framework.
Lateral movement is usually the next step and that can involve many different techniques. Again, the Alerting Dashboard identifies lateral movement techniques with details into the specific activity that triggered the alert.
Ransomware and RDP are a dangerous combination. Protecting your remote end users requires a good, secure baseline configuration of Endpoint Security with a Firewall and Self Protection enabled and access to adaptable capability such as Adaptive Threat Protection with Enhanced Remediation. The Enhanced Remediation feature is only available starting in version ENS 10.7, so if you are running older versions of ENS or even VSE (yikes), then it is time to upgrade.
However, stopping targeted ransomware from having an impact on the business requires more than prevention. Both ePO and EDR provide the capability for proactive detection, faster investigations and continuous hunting.
Finally, adaptability requires threat intelligence. McAfee Advanced Threat Researchers and Labs are actively monitoring the threat landscape and continuously updating McAfee Global Threat Intelligence systems. Make sure your Endpoint Security and other McAfee products are using GTI for the latest protection.
For more information on targeted ransomware attacks and techniques, see ATR Blog.
For more details about how to securing RDP access in general, you can refer to a previous McAfee blog.
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