Techniques
Sample rules
Linux Possible Append Cronjob Entry on Existing Cronjob File
- source: splunk
- technicques:
- T1053.003
Description
The following analytic detects potential tampering with cronjob files on a Linux system by identifying ’echo’ commands that append code to existing cronjob files. It leverages logs from Endpoint Detection and Response (EDR) agents, focusing on process names, parent processes, and command-line executions. This activity is significant because adversaries often use it for persistence or privilege escalation. If confirmed malicious, this could allow attackers to execute unauthorized code automatically, leading to system compromises and unauthorized data access, thereby impacting business operations and data integrity.
Detection logic
| tstats `security_content_summariesonly` count from datamodel=Endpoint.Processes where Processes.process = "*echo*" AND Processes.process IN("*/etc/cron*", "*/var/spool/cron/*", "*/etc/anacrontab*") 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)`
| `linux_possible_append_cronjob_entry_on_existing_cronjob_file_filter`
Linux Auditd Possible Append Cronjob Entry On Existing Cronjob File
- source: splunk
- technicques:
- T1053.003
Description
The following analytic detects potential tampering with cronjob files on a Linux system. It leverages logs from Linux Auditd, focusing on events of type PATH or CWD. This activity could be significant because adversaries often use it for persistence or privilege escalation. Correlate this with related EXECVE or PROCTITLE events to identify the process or user responsible for the access or modification. If confirmed malicious, this could allow attackers to execute unauthorized code automatically, leading to system compromises and unauthorized data access, thereby impacting business operations and data integrity.
Detection logic
`linux_auditd` (type=PATH OR type=CWD)
| rex "msg=audit\([^)]*:(?<audit_id>\d+)\)"
| stats
values(type) as types
values(name) as names
values(nametype) as nametype
values(cwd) as cwd_list
values(_time) as event_times
by audit_id, host
| eval current_working_directory = coalesce(mvindex(cwd_list, 0), "N/A")
| eval candidate_paths = mvmap(names, if(match(names, "^/"), names, current_working_directory + "/" + names))
| eval matched_paths = mvfilter(match(candidate_paths, "/etc/cron.*
|.*/cron/.*
|/etc/anacrontab.*"))
| eval match_count = mvcount(matched_paths)
| eval reconstructed_path = mvindex(matched_paths, 0)
| eval e_time = mvindex(event_times, 0)
| where match_count > 0
| rename host as dest
| stats count min(e_time) as firstTime max(e_time) as lastTime
values(nametype) as nametype
by current_working_directory
reconstructed_path
match_count
dest
audit_id
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `linux_auditd_possible_append_cronjob_entry_on_existing_cronjob_file_filter`