From 676bbd9b8eab6b32895c44ebed4bd134df9e6b5e Mon Sep 17 00:00:00 2001 From: Michael Haag <5632822+MHaggis@users.noreply.github.com> Date: Mon, 2 Dec 2024 11:01:06 -0700 Subject: [PATCH 1/2] Update linux_auditd_file_permission_modification_via_chmod.yml MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Update based on feedback from Ivar Nygård Thank you! --- .../linux_auditd_file_permission_modification_via_chmod.yml | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/detections/endpoint/linux_auditd_file_permission_modification_via_chmod.yml b/detections/endpoint/linux_auditd_file_permission_modification_via_chmod.yml index 3e4d9f7bc6..402ddd043f 100644 --- a/detections/endpoint/linux_auditd_file_permission_modification_via_chmod.yml +++ b/detections/endpoint/linux_auditd_file_permission_modification_via_chmod.yml @@ -1,14 +1,14 @@ name: Linux Auditd File Permission Modification Via Chmod id: 5f1d2ea7-eec0-4790-8b24-6875312ad492 -version: 2 -date: '2024-09-30' +version: 3 +date: '2024-12-02' author: Teoderick Contreras, Splunk status: production type: Anomaly description: The following analytic detects suspicious file permission modifications using the `chmod` command, which may indicate an attacker attempting to alter access controls on critical files or directories. Such modifications can be used to grant unauthorized users elevated privileges or to conceal malicious activities by restricting legitimate access. By monitoring for unusual or unauthorized `chmod` usage, this analytic helps identify potential security breaches, allowing security teams to respond promptly to prevent privilege escalation, data tampering, or other unauthorized actions on the system. data_source: - Linux Auditd Proctitle -search: '`linux_auditd` `linux_auditd_normalized_proctitle_process` | rename host as dest | where LIKE(process_exec, "%chmod%") AND (LIKE(process_exec, "% 777 %") OR LIKE(process_exec, "% 755 %") OR LIKE(process_exec, "%x%") OR LIKE(process_exec, "% 754 %") OR LIKE(process_exec, "% 700 %")) | stats count min(_time) as firstTime max(_time) as lastTime by process_exec proctitle dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`| `linux_auditd_file_permission_modification_via_chmod_filter`' +search: '`linux_auditd` `linux_auditd_normalized_proctitle_process` | rename host as dest | where LIKE(process_exec, "%chmod%") AND (LIKE(process_exec, "% 777 %") OR LIKE(process_exec, "% 755 %") OR LIKE(process_exec, "%+%x%") OR LIKE(process_exec, "% 754 %") OR LIKE(process_exec, "% 700 %")) | stats count min(_time) as firstTime max(_time) as lastTime by process_exec proctitle dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`| `linux_auditd_file_permission_modification_via_chmod_filter`' 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 use this application for automation purposes. Please update the filter macros to remove false positives. references: From 798c27c8448e7be4267c1c5ddd13a35345a502aa Mon Sep 17 00:00:00 2001 From: Michael Haag <5632822+MHaggis@users.noreply.github.com> Date: Tue, 3 Dec 2024 11:02:08 -0700 Subject: [PATCH 2/2] reference --- .../linux_auditd_file_permission_modification_via_chmod.yml | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/detections/endpoint/linux_auditd_file_permission_modification_via_chmod.yml b/detections/endpoint/linux_auditd_file_permission_modification_via_chmod.yml index 402ddd043f..d5e6e552c8 100644 --- a/detections/endpoint/linux_auditd_file_permission_modification_via_chmod.yml +++ b/detections/endpoint/linux_auditd_file_permission_modification_via_chmod.yml @@ -2,7 +2,7 @@ name: Linux Auditd File Permission Modification Via Chmod id: 5f1d2ea7-eec0-4790-8b24-6875312ad492 version: 3 date: '2024-12-02' -author: Teoderick Contreras, Splunk +author: Teoderick Contreras, Splunk, Ivar Nygård status: production type: Anomaly description: The following analytic detects suspicious file permission modifications using the `chmod` command, which may indicate an attacker attempting to alter access controls on critical files or directories. Such modifications can be used to grant unauthorized users elevated privileges or to conceal malicious activities by restricting legitimate access. By monitoring for unusual or unauthorized `chmod` usage, this analytic helps identify potential security breaches, allowing security teams to respond promptly to prevent privilege escalation, data tampering, or other unauthorized actions on the system.