CrowdStrike Falcon offers cloud-delivered solutions across endpoints, cloud workloads, identity and data; providing responders remote visibility across the enterprise and enabling instant access to the "who, what, when, where, and how" of a cyber attack. Several files were identified by this broad query, however, it was ultimately determined that only the file under \inetpub\wwwroot\aspnet_client\system_web directory was the malicious webshell. The issue persists and the desired executable cannot run. Whenever responding to activity like this, the Falcon Complete team puts an emphasis on understanding what has been detected, and how the activity can be contained and remediated to ensure our customers remain protected. In Windows Server 2016 and later, the predefined exclusions delivered by Security intelligence updates only exclude the default paths for a role or feature. As you are aware, falcon sensor does not work like traditional AV solutions. The following sections contain the exclusions that are delivered with automatic exclusions file paths and file types. Open Windows Defender Security Center. To do that, see the following articles: If you're looking for Antivirus related information for other platforms, see: More info about Internet Explorer and Microsoft Edge, Configure and validate exclusions based on file name, extension, and folder location, Configure and validate exclusions for files opened by processes, Onboard Windows servers to the Microsoft Defender for Endpoint service, Automatic exclusions on Windows Server 2016 or later, Configure the list of exclusions based on folder name or file extension, Use PowerShell cmdlets to configure and run Microsoft Defender Antivirus, Use PowerShell with Microsoft Defender Antivirus, Set preferences for Microsoft Defender for Endpoint on macOS, macOS Antivirus policy settings for Microsoft Defender Antivirus for Intune, Set preferences for Microsoft Defender for Endpoint on Linux, Configure Defender for Endpoint on Android features, Configure Microsoft Defender for Endpoint on iOS features, Exclusions for Microsoft Defender for Endpoint and Microsoft Defender Antivirus, Configure and validate exclusions for Microsoft Defender Antivirus scans, Common mistakes to avoid when defining exclusions, Customize, initiate, and review the results of Microsoft Defender Antivirus scans and remediation, Microsoft Defender Antivirus in Windows 10, Describes the two main types of automatic exclusions and includes a detailed list of automatic exclusions, Includes important considerations and procedures describing how to opt out of automatic exclusions, Provides links to how-to information for defining custom exclusions. Right-click the Group Policy Object you want to configure, and then select Edit. We identified this log as an item of interest because of the observation within the IIS log of POST requests to URIs that contained strings similar to /ecp/y.js. This document covers blacklisting and whitelisting steps. These POSTs corresponded to the command execution seen in the initial detections for the activity. Expand the tree to Windows components > Microsoft Defender Antivirus > Exclusions. This analysis included but was not limited to, analysis of IIS log files, ECP log files, and Event logs from the host., When investigating any web exploitation, parsing through the web logs is a valuable source of information. Enable or disable policies, and add granular inclusions and exclusions to control false alarms. Those methods include machine learning, exploit blocking, blacklisting and indicators of attack. As you can see here, if I double click the file in its current form, it will go ahead and open up. Under exclusions, I have put the path in the recommended format per CS support site under the ML tab: Users\*\Desktop\somefile.exe as well as scoped the exclusion to only affect one Group. Looking around the timestamps that these files were written, Falcon Complete uncovered a pattern of behavior in multiple customers IIS logs, thus indicating that this log pattern likely has to do with the exploitation activity.. This article describes the recommended antivirus exclusions for Hyper-V hosts for optimal operation. Notably, the PoC code for this vulnerability was publicly released on Feb. 15.. This article includes the following sections: On Windows Server 2016 or later, you should not need to define the following exclusions: Because Microsoft Defender Antivirus is built in, it does not require exclusions for operating system files on Windows Server 2016 or later. That's good to hear. Operating system exclusions and server role exclusions do not appear in the standard exclusion lists that are shown in the Windows Security app. This functionality greatly speeds the scan time and aids a responder in quickly pinpointing adversary activity on a suspect system. Detect, prevent, and respond to attacks even malware-free intrusionsat any stage, with next-generation endpoint protection. These exclusions do not appear in the standard exclusion lists that are shown in the Windows Security app. CrowdStrike Falcon offers cloud-delivered solutions across endpoints, cloud workloads, identity and data; providing responders remote visibility across the enterprise and enabling instant access to the "who, what, when, where, and how" of a cyber attack. In nearly all instances, the webshell dropped was observed to be a China Chopper-like webshell.. This folder is specified in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\Printers\DefaultSpoolDirectory. This campaign is scanning and automatically exploiting multiple zero-day vulnerabilities (CVE-2021-26855, CVE-2021-26857, CVE-2021-26858 and CVE-2021-27065) to drop an ASPX-based webshell onto vulnerable Microsoft Exchange servers. The POST appears to be a central part of the exploit chain in being able to write the webshells to the hosts. Of note, Falcon Complete was unable to collect a copy of y.js from any of this activity to confirm the files purpose. Oversee all file changes with summary and detailed view dashboards - reduce alert fatigue by quickly targeting changes to critical files and systems. More information on associated patches can be found from in the following. Despite the remaining vulnerabilities, with no effective patch mitigations, Falcon Complete prevented and contained this second attempt as well. Im going to highlight both of them. This section lists the file and folder exclusions that are delivered automatically when you install the File and Storage Services role. High CPU utilization, application crash, take more to load etc. As you can see here, Windows is unable to execute the file. We will be releasing regularly scheduled additions over the coming months the same. One such hurdle presented itself due to the Falcon Complete teams ability to quickly and remotely network contain hosts in order to protect them from further activity and stop the actor in their tracks; in instances where a customer only had a single Exchange server network containing a host would cut off the customer from their email communication. Press J to jump to the feed. Starting Sunday, Feb. 28, the Falcon OverWatch team of threat hunters saw the first signs of a novel intrusion. Enable or disable policies, and add granular inclusions and exclusions to control false alarms. file3.exe) of c:\dir2\file2.exe by a file exclusion rule of c:\dir2\file2.exe? Today were going to show you how CrowdStrikes Falcon host offers simple blacklisting and whitelisting of files in your environment on your endpoints. This section lists the folder exclusions and the process exclusions that are delivered automatically when you install the Web Server role. In this case, we want to define the parent image filename as cmd.exe and the image filename as calc.exe. Gain central visibility into all critical file changes with relevant, intuitive dashboards displaying valuable information on what changes, who changed it, and how the files and folders were changed. To learn more, see, Server roles and any files that are added through server roles. CrowdResponse will allow the security community at large to consume some of the publically available indictors that we discuss in our frequent blog posts. And we are able to remotely connect to a machine thats also running the TeamViewer client. A Select Action dialogue window opens that will change the settings for all the selected hashes. The initial infection vector was still unknown at this point. In addition to understanding this critical data, being able to also understand the root cause of exploitation is extremely valuable as it helps to more clearly identify how exploitation occurred in the first place, and implement additional safeguards to prevent further exploitation in the future. On your Group Policy management computer, open the Group Policy Management Console. Assembly variation observed (Click to enlarge). The green shield confirms that the process was prevented as a result of the custom rule. The FRS Database log file folder is specified in the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Ntfrs\Parameters\DB Log File Directory, The FRS staging folder. This gives customers the ability to create behavioral detections based on what they know about their specific applications and environment.. You can find more information in our documentation (login required, not sure if you have one ahead of onboarding): https://falcon.crowdstrike.com/support/documentation/68/detection-and-prevention-policies#file-exclusions. The second I hit Apply, within seconds these two hashes will be prevented from executing in my environment moving forward. For wildcards, use current Windows operating system standards: Wildcards can be used for file and folder paths. It is unclear why they would execute this command, although it could simply be an indication their intent was to deny legitimate admins the capability to thwart their actions. Custom and duplicate exclusions do not conflict with automatic exclusions. processes writing and compiling temporary DLLs on disk. This integration can be used in two ways. In this case, we can see TeamViewer, maybe V&C, maybe BitTorrent, in my case. If you have folders and files types that you wish to exclude from the behaviour engine then these can be manually added in the management console. Exclude the following installation folders and their sub-folders from on-access virus scan. This section lists the file and folder exclusions and the process exclusions that are delivered automatically when you install the DNS Server role. Welcome to the CrowdStrike subreddit. Running Falcon Pro sensor on a couple of SQL servers currently. The majority of these cases involve the presence of Bitdefender Antivirus and are resolved by configuring the above Process-Specific Exclusions. 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crowdstrike file path exclusion