Suspicious Schtasks Schedule Types

Severity: high
Author: Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects scheduled task creations or modification on a suspicious schedule type

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1053.005` Scheduled Task/Job: Scheduled Task
Persistence	`T1053.005` Scheduled Task/Job: Scheduled Task
Privilege Escalation	`T1053.005` Scheduled Task/Job: Scheduled Task

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_img`

or:
Image|endswith: '\schtasks.exe'
OriginalFileName: schtasks.exe

Stage 2: `all of selection_time`

or:
CommandLine|contains: ' ONCE '
CommandLine|contains: ' ONIDLE '
CommandLine|contains: ' ONLOGON '
CommandLine|contains: ' ONSTART '

Stage 3: `not 1 of filter_privs`

or:
CommandLine|contains: ' SYSTEM'
CommandLine|contains: HIGHEST
CommandLine|contains: 'NT AUT'

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
`CommandLine`	match	`ONCE` corpus 2 (sigma 2) `ONIDLE` corpus 2 (sigma 2) `ONLOGON` corpus 2 (sigma 2) `ONSTART` corpus 2 (sigma 2) `SYSTEM` corpus 2 (sigma 2) `HIGHEST` corpus 2 (sigma 2) `NT AUT` corpus 4 (sigma 4)
`Image`	ends_with	`\schtasks.exe` corpus 45 (sigma 45)
`OriginalFileName`	eq	`schtasks.exe` corpus 14 (sigma 14)

Neighbors

Equivalent rules

1 other rule has the same matching logic as this one. Useful for cross-vendor comparison or picking the variant your stack supports. See eq_0003.