Kubernetes CronJob/Job Modification

Status: test
Severity: medium
Log source: product kubernetes, service audit
Author: kelnage
Source: github.com/SigmaHQ/sigma

Detects when a Kubernetes CronJob or Job is created or modified. A Kubernetes Job creates one or more pods to accomplish a specific task, and a CronJob creates Jobs on a recurring schedule. An adversary can take advantage of this Kubernetes object to schedule Jobs to run containers that execute malicious code within a cluster, allowing them to achieve persistence.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	No specific technique
Persistence	No specific technique
Privilege Escalation	No specific technique

Event coverage

Provider	Event	Title
Kubernetes-cronjobs	create-cronjobs	create cronjobs
Kubernetes-cronjobs	update-cronjobs	update cronjobs
Kubernetes-cronjobs	patch-cronjobs	patch cronjobs
Kubernetes-cronjobs	delete-cronjobs	delete cronjobs
Kubernetes-jobs	create-jobs	create jobs
Kubernetes-jobs	update-jobs	update jobs
Kubernetes-jobs	patch-jobs	patch jobs
Kubernetes-jobs	delete-jobs	delete jobs

Rules detecting the same action

Other rules on this platform that filter on the same API call or operation.

Kubernetes Sensitive RBAC Change Followed by Workload Modification (Elastic)
Unusual Kubernetes Sensitive Workload Modification (Elastic)

Rule body yaml

title: Kubernetes CronJob/Job Modification
id: 0c9b3bda-41a6-4442-9345-356ae86343dc
related:
    - id: cd3a808c-c7b7-4c50-a2f3-f4cfcd436435
      type: similar
status: test
description: |
    Detects when a Kubernetes CronJob or Job is created or modified.
    A Kubernetes Job creates one or more pods to accomplish a specific task, and a CronJob creates Jobs on a recurring schedule.
    An adversary can take advantage of this Kubernetes object to schedule Jobs to run containers that execute malicious code within a cluster, allowing them to achieve persistence.
references:
    - https://kubernetes.io/docs/reference/config-api/apiserver-audit.v1/
    - https://www.redhat.com/en/blog/protecting-kubernetes-against-mitre-attck-persistence#technique-33-kubernetes-cronjob
author: kelnage
date: 2024-07-11
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.execution
logsource:
    product: kubernetes
    service: audit
detection:
    selection:
        objectRef.apiGroup: 'batch'
        objectRef.resource:
            - 'cronjobs'
            - 'jobs'
        verb:
            - 'create'
            - 'delete'
            - 'patch'
            - 'replace'
            - 'update'
    condition: selection
falsepositives:
    - Modifying a Kubernetes Job or CronJob may need to be done by a system administrator.
    - Automated processes may need to take these actions and may need to be filtered.
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    objectRef.apiGroup: 'batch'
    objectRef.resource:
        - 'cronjobs'
        - 'jobs'
    verb:
        - 'create'
        - 'delete'
        - 'patch'
        - 'replace'
        - 'update'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`objectRef.apiGroup`	eq	`batch`
`objectRef.resource`	eq	`cronjobs` `jobs`
`verb`	eq	`create` `delete` `patch` `replace` `update`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Kubernetes CronJob/Job Modification

MITRE ATT&CK coverage

Event coverage

Rules detecting the same action

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

Kubernetes CronJob/Job Modification

MITRE ATT&CK coverage

Event coverage

Rules detecting the same action

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`