File Download or Read to Pipe Execution
Description
The following analytic detects the use of download or file reading utilities from Windows, Linux or MacOS to download or read the contents of a file from a remote or local source and pipe it directly to a shell for execution. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions. This activity is significant as it is commonly associated with malicious actions like coinminers and exploits such as CVE-2021-44228 in Log4j. If confirmed malicious, this behavior could allow attackers to execute arbitrary code, potentially leading to system compromise and unauthorized access to sensitive data.
Query · spl
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
as lastTime
from datamodel=Endpoint.Processes where
``` This aims to cover download utilities and file reading ones ```
Processes.process IN (
"*.DownloadFile(*",
"*.DownloadString(*",
"*ASCII.GetString*",
"*bitsadmin*",
"*certutil*",
"*curl*",
"*Invoke-RestMethod*",
"*Invoke-WebRequest*",
"*irm*",
"*iwr *",
"*mshta*",
"*wget*"
)
Processes.process IN ("*|*")
(
``` Linux / MacOS ```
Processes.process IN (
"*bash*",
"*csh*",
"*dash*",
"*fish*",
"*ksh*",
"*rbash*",
"*tcsh*",
"*zsh*"
)
OR
``` Because the "sh" string can overlap and is a short atom we treat it in a special case ```
Processes.process IN (
"*|sh"
"* sh*"
)
OR
``` Windows ```
Processes.process IN ("*IEX*", "*Invoke-Expression*")
)
by Processes.action Processes.dest Processes.original_file_name Processes.parent_process
Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id
Processes.parent_process_name Processes.parent_process_path Processes.process
Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id
Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user
Processes.user_id Processes.vendor_product
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `file_download_or_read_to_pipe_execution_filter`
Implementation guide
The detection is based on data that originates from Endpoint Detection
and Response (EDR) agents. These agents are designed to provide security-related
telemetry from the endpoints where the agent is installed. To implement this search,
you must ingest logs that contain the process GUID, process name, and parent process.
Additionally, you must ingest complete command-line executions. These logs must
be processed using the appropriate Splunk Technology Add-ons that are specific to
the EDR product. The logs must also be mapped to the Processes node of the Endpoint
data model. Use the Splunk Common Information Model (CIM) to normalize the field
names and speed up the data modeling process.
Known false positives
- False positives should be limited, however filtering may be required.
Analyst notes
Known false positives: False positives should be limited, however filtering may be required.