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Description

The following analytic identifies the execution of suspicious processes typically associated with webshell activity on web servers. It detects when processes like cmd.exe, powershell.exe, or bash.exe are spawned by web server processes such as w3wp.exe or nginx.exe. This behavior is significant as it may indicate an adversary exploiting a web application vulnerability to install a webshell, providing persistent access and command execution capabilities. If confirmed malicious, this activity could allow attackers to maintain control over the compromised server, execute arbitrary commands, and potentially escalate privileges or exfiltrate sensitive data.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2024-05-20
  • Author: Steven Dick
  • ID: 22597426-6dbd-49bd-bcdc-4ec19857192f

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1505 Server Software Component Persistence
T1505.003 Web Shell Persistence
Kill Chain Phase
  • Installation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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| tstats `security_content_summariesonly` count max(_time) as lastTime, min(_time) as firstTime from datamodel=Endpoint.Processes where (Processes.process_name IN ("arp.exe","at.exe","bash.exe","bitsadmin.exe","certutil.exe","cmd.exe","cscript.exe", "dsget.exe","dsquery.exe","find.exe","findstr.exe","fsutil.exe","hostname.exe","ipconfig.exe","ksh.exe","nbstat.exe", "net.exe","net1.exe","netdom.exe","netsh.exe","netstat.exe","nltest.exe","nslookup.exe","ntdsutil.exe","pathping.exe", "ping.exe","powershell.exe","pwsh.exe","qprocess.exe","query.exe","qwinsta.exe","reg.exe","rundll32.exe","sc.exe", "scrcons.exe","schtasks.exe","sh.exe","systeminfo.exe","tasklist.exe","tracert.exe","ver.exe","vssadmin.exe", "wevtutil.exe","whoami.exe","wmic.exe","wscript.exe","wusa.exe","zsh.exe") AND Processes.parent_process_name IN ("w3wp.exe", "http*.exe", "nginx*.exe", "php*.exe", "php-cgi*.exe","tomcat*.exe")) by Processes.dest,Processes.user,Processes.parent_process,Processes.parent_process_name,Processes.process,Processes.process_name 
| `drop_dm_object_name("Processes")` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `detect_webshell_exploit_behavior_filter`

Macros

The SPL above uses the following Macros:

:information_source: detect_webshell_exploit_behavior_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Processes.dest
  • Processes.user
  • Processes.parent_process
  • Processes.parent_process_name
  • Processes.process
  • Processes.process_name

How To Implement

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

Legitimate OS functions called by vendor applications, baseline the environment and filter before enabling. Recommend throttle by dest/process_name

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
80.0 100 80 Webshell Exploit Behavior - $parent_process_name$ spawned $process_name$ on $dest$.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 3