| ID | Technique | Tactic |
|---|---|---|
| T1548.003 | Sudo and Sudo Caching | Defense Evasion |
| T1548 | Abuse Elevation Control Mechanism | Privilege Escalation |
Detection: Linux Sudoers Tmp File Creation
Description
The following analytic detects the creation of the "sudoers.tmp" file, which occurs when editing the /etc/sudoers file using visudo or another editor on a Linux platform. This detection leverages filesystem data to identify the presence of "sudoers.tmp" files. Monitoring this activity is crucial as adversaries may exploit it to gain elevated privileges on a compromised host. If confirmed malicious, this activity could allow attackers to modify sudoers configurations, potentially granting them unauthorized access to execute commands as other users, including root, thereby compromising the system's security.
Search
1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_path IN ("*sudoers.tmp*") by Filesystem.dest Filesystem.file_name Filesystem.process_guid Filesystem.file_path
3| `drop_dm_object_name(Filesystem)`
4| `security_content_ctime(lastTime)`
5| `security_content_ctime(firstTime)`
6| `linux_sudoers_tmp_file_creation_filter`
Data Source
| Name | Platform | Sourcetype | Source | Supported App |
|---|---|---|---|---|
| Sysmon for Linux EventID 11 |  Linux |
'sysmon:linux' |
'Syslog:Linux-Sysmon/Operational' |
N/A |
Macros Used
| Name | Value |
|---|---|
| security_content_ctime | convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$) |
| linux_sudoers_tmp_file_creation_filter | search * |
linux_sudoers_tmp_file_creation_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
MITRE ATT&CK
Kill Chain Phases
NIST
CIS
Threat Actors
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
| Setting | Value |
|---|---|
| Disabled | true |
| Cron Schedule | 0 * * * * |
| Earliest Time | -70m@m |
| Latest Time | -10m@m |
| Schedule Window | auto |
| Creates Risk Event | True |
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.
Implementation
To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you can use the Add-on for Linux Sysmon from Splunkbase.
Known False Positives
administrator or network operator can execute this command. Please update the filter macros to remove false positives.
Associated Analytic Story
Risk Based Analytics (RBA)
| Risk Message | Risk Score | Impact | Confidence |
|---|---|---|---|
| A file $file_name$ is created in $file_path$ on $dest$ | 72 | 80 | 90 |
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
References
Detection Testing
| Test Type | Status | Dataset | Source | Sourcetype |
|---|---|---|---|---|
| Validation | ✅ Passing | N/A | N/A | N/A |
| Unit | ✅ Passing | Dataset | Syslog:Linux-Sysmon/Operational |
sysmon:linux |
| Integration | ✅ Passing | Dataset | Syslog:Linux-Sysmon/Operational |
sysmon:linux |
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: GitHub | Version: 2