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P4T12ICK
83 lines
2.9 KiB
YAML
83 lines
2.9 KiB
YAML
name: Linux Decode Base64 to Shell
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id: 637b603e-1799-40fd-bf87-47ecbd551b66
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version: 1
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date: '2022-07-27'
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author: Michael Haag, Splunk
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status: production
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type: TTP
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description: The following analytic identifies base64 being decoded and passed to
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a Linux shell.
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data_source:
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- Sysmon Event ID 1
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search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
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as lastTime from datamodel=Endpoint.Processes where Processes.process IN ("*base64
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-d*","*base64 --decode*") AND Processes.process="*|*" `linux_shells` by Processes.dest
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Processes.user Processes.parent_process_name Processes.process_name Processes.process
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Processes.process_id Processes.parent_process_id | `drop_dm_object_name(Processes)`
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| `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `linux_decode_base64_to_shell_filter`'
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how_to_implement: To successfully implement this search you need to be ingesting information
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on process that include the name of the process responsible for the changes from
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your endpoints into the `Endpoint` datamodel in the `Processes` node. In addition,
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confirm the latest CIM App 4.20 or higher is installed and the latest TA for the
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endpoint product.
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known_false_positives: False positives may be present based on legitimate software
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being utilized. Filter as needed.
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references:
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- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1027/T1027.md#atomic-test-1---decode-base64-data-into-script
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- https://redcanary.com/blog/lateral-movement-with-secure-shell/
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- https://linux.die.net/man/1/base64
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tags:
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analytic_story:
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- Linux Living Off The Land
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asset_type: Endpoint
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confidence: 50
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impact: 50
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message: An instance of $parent_process_name$ spawning $process_name$ was identified
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on endpoint $dest$ by user $user$ decoding base64 and passing it to a shell.
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mitre_attack_id:
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- T1027
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- T1059.004
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observable:
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- name: user
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type: User
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role:
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- Victim
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- name: dest
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type: Hostname
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role:
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- Victim
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- name: parent_process_name
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type: Process
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role:
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- Parent Process
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- name: process_name
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type: Process
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role:
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- Child Process
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product:
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- Splunk Enterprise
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- Splunk Enterprise Security
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- Splunk Cloud
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required_fields:
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- _time
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- Processes.dest
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- Processes.user
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- Processes.parent_process_name
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- Processes.parent_process
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- Processes.original_file_name
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- Processes.process_name
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- Processes.process
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- Processes.process_id
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- Processes.parent_process_path
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- Processes.process_path
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- Processes.parent_process_id
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risk_score: 25
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security_domain: endpoint
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tests:
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- name: True Positive Test
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attack_data:
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- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1027/atomic_red_team/linux-sysmon.log
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source: Syslog:Linux-Sysmon/Operational
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sourcetype: sysmon_linux
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update_timestamp: true
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