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Description

The following analytic detects attempts to access or dump the contents of /etc/passwd and /etc/shadow files on Linux systems. It leverages data from Linux Auditd, focusing on processes like 'cat', 'nano', 'vim', and 'vi' accessing these files. This activity is significant as it may indicate credential dumping, a technique used by adversaries to gain persistence or escalate privileges. If confirmed malicious, privileges. If confirmed malicious, attackers could obtain hashed passwords for offline cracking, leading to unauthorized access and potential system compromise.

  • Type: Anomaly

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-09-04
  • Author: Teoderick Contreras, Splunk
  • ID: 0419cb7a-57ea-467b-974f-77c303dfe2a3

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1003.008 /etc/passwd and /etc/shadow Credential Access
T1003 OS Credential Dumping Credential Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`linux_auditd` `linux_auditd_normalized_proctitle_process` 
| rename host as dest 
| where (LIKE (process_exec, "%shadow%") OR LIKE (process_exec, "%passwd%")) AND (LIKE (process_exec, "%cat %") OR LIKE (process_exec, "%nano %")OR LIKE (process_exec, "%vim %") OR LIKE (process_exec, "%vi %")) 
| stats count min(_time) as firstTime max(_time) as lastTime by process_exec proctitle normalized_proctitle_delimiter dest 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)`
| `linux_auditd_possible_access_to_credential_files_filter`

Macros

The SPL above uses the following Macros:

:information_source: linux_auditd_possible_access_to_credential_files_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
  • proctitle

How To Implement

To implement this detection, the process begins by ingesting auditd data, that consist SYSCALL, TYPE, EXECVE and PROCTITLE events, which captures command-line executions and process details on Unix/Linux systems. These logs should be ingested and processed using Splunk Add-on for Unix and Linux (https://splunkbase.splunk.com/app/833), which is essential for correctly parsing and categorizing the data. The next step involves normalizing the field names to match the field names set by the Splunk Common Information Model (CIM) to ensure consistency across different data sources and enhance the efficiency of data modeling. This approach enables effective monitoring and detection of linux endpoints where auditd is deployed

Known False Positives

Administrator or network operator can execute this command. Please update the filter macros to remove false positives.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
25.0 50 50 A [$process_exec$] event occurred on host - [$dest$] to access or dump the contents of /etc/passwd and /etc/shadow files.

: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

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