crowdstrike-falcon-queries

A collection of Splunk's Search Processing Language (SPL) for Threat Hunting with CrowdStrike Falcon

Developed and maintained by Intelligent Response team, i-secure co., Ltd.

Execution of Renamed Executables
List of Living Off The Land Binaries with Network Connections
Suspicious Network Connections from Processes
Suspicious PowerShell Process, Spawned from Explorer, with Network Connections

Execution of Renamed Executables

This query is inspired by Red Canary's research. For explanation in Thai, please find in our blog.

Idea:

Identify if there are any events with file renaming activity — found that CrowdStrike Falcon already had a specific field name for executables, NewExecutableRenamed.
Correlate TargetFileName field on NewExecutableRenamed event with a filename available on ImageFileName field on ProcessRollup2 event.
Create a result table with ComputerName, timestamp, ImageFileName, and CommandLine as columns.

event_simpleName="NewExecutableRenamed"
| rename TargetFileName as ImageFileName
| join ImageFileName 
    [ search event_simpleName="ProcessRollup2" ]
| table ComputerName SourceFileName ImageFileName CommandLine

List of Living Off The Land Binaries with Network Connections

This query is inspired by Red Canary's research. For explanation in Thai, please find in our blog.

Idea:

Identify if there are any events relating to network activity — found that CrowdStrike Falcon has DnsRequest and NetworkConnectIP4 events. We’re going to use the DnsRequest event in this query.
Correlate ContextProcessId field from DnsRequest event with TargetProcessId on ProcessRollup2 event.
Create a sub-search to filter only known LOLBas files.
Create a result table with ComputerName, timestamp, ImageFileName, and CommandLine as columns.

Because our hunting query required a list of known LOL binaries/files for filtering, we need to enumerate a list of files available on LOLBAS-Project/LOLBas, which can simple by done by a grep expression: grep -Poh "(?<=Name:\s)[A-Za-z0-9_-]+.exe$" OSBinaries/

event_simpleName="DnsRequest"
| rename ContextProcessId as TargetProcessId
| join TargetProcessId 
    [ search event_simpleName="ProcessRollup2" (FileName=Atbroker.exe OR FileName=Bash.exe OR FileName=Bitsadmin.exe OR FileName=Certutil.exe OR FileName=Cmd.exe OR FileName=Cmstp.exe OR FileName=Control.exe OR FileName=Cscript.exe OR FileName=Csc.exe OR FileName=Dfsvc.exe OR FileName=Diskshadow.exe OR FileName=Dnscmd.exe OR FileName=Esentutl.exe OR FileName=Eventvwr.exe OR FileName=Expand.exe OR FileName=Extexport.exe OR FileName=Extrac32.exe OR FileName=Findstr.exe OR FileName=Forfiles.exe OR FileName=Ftp.exe OR FileName=Gpscript.exe OR FileName=Hh.exe OR FileName=Ie4uinit.exe OR FileName=Ieexec.exe OR FileName=Infdefaultinstall.exe OR FileName=Installutil.exe OR FileName=Jsc.exe OR FileName=Makecab.exe OR FileName=Mavinject.exe OR FileName=Mmc.exe OR FileName=Msconfig.exe OR FileName=Msdt.exe OR FileName=Mshta.exe OR FileName=Msiexec.exe OR FileName=Odbcconf.exe OR FileName=Pcalua.exe OR FileName=Pcwrun.exe OR FileName=Presentationhost.exe OR FileName=Print.exe OR FileName=Regasm.exe OR FileName=Regedit.exe OR FileName=Register-cimprovider.exe OR FileName=Regsvcs.exe OR FileName=Regsvr32.exe OR FileName=Reg.exe OR FileName=Replace.exe OR FileName=Rpcping.exe OR FileName=Rundll32.exe OR FileName=Runonce.exe OR FileName=Runscripthelper.exe OR FileName=Schtasks.exe OR FileName=Scriptrunner.exe OR FileName=Sc.exe OR FileName=SyncAppvPublishingServer.exe OR FileName=Verclsid.exe OR FileName=Wab.exe OR FileName=Wmic.exe OR FileName=Wscript.exe OR FileName=Wsreset.exe OR FileName=Xwizard.exe) ] 
| table ComputerName timestamp ImageFileName DomainName CommandLine

Suspicious Network Connections from Processes

This query is inspired by Red Canary's research. For explanation in Thai, please find in our blog.

Idea:

Identify network activities recorded by CrowdStrike falcon with the DNSRequest or NetworkConnectIP4 event, in this query we will use NetworkConnectIP4.
Correlate ContextProcessId_decimal with TargetProcessId_decimal on ProcessRollup2 events
Create a result table with RemoteIP, RemotePort_decimal, ImageFileName, UserName and UserSid_readable.

event_simpleName="NetworkConnectIP4"
| rename ContextProcessId_decimal as TargetProcessId_decimal
| join TargetProcessId_decimal 
    [ search event_simpleName=ProcessRollup2 ]
| table RemoteIP RemotePort_decimal ImageFileName UserName UserSid_readabl

Suspicious PowerShell Process, Spawned from Explorer, with Network Connections

This query is inspired by Red Canary's research. For explanation in Thai, please find in our blog.

Idea:

Identify network activities recorded by CrowdStrike falcon with the DNSRequest event
Correlate ContextProcessId field on DNSRequest with TargetProcessId on ProcessRollup2 and SyntheticProcessRollup2 events
With a combination of rename-join-subsearch, the outer nested sub-search will be created and responsible for identifying a TargetProcessId_decimal of Explorer.exe from ProcessRollup2 event, and then join with the inner nested sub-search that responsible to find PowerShell.exe which has the same ParentProcessId_decimal as TargetProcessId_decimal of Explorer.exe
Create a result table with ComputerName, timestamp, ImageFileName, DomainName, and CommandLine

Be aware that whenever ParentProcessId_decimal is used, you may need to extend a search scope longer than usual. Because some processes, especially system processes, usually have high uptime but been abused recently.

event_simpleName="DnsRequest"
| rename ContextProcessId as TargetProcessId
| join TargetProcessId 
    [ search (event_simpleName="ProcessRollup2" OR event_simpleName="SyntheticProcessRollup2") AND FileName="explorer.exe" 
    | rename TargetProcessId_decimal as ParentProcessId_decimal 
    | join ParentProcessId_decimal 
        [ search event_simpleName="ProcessRollup2" FileName="powershell.exe" ]] 
| table ComputerName timestamp ImageFileName DomainName CommandLine

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