Scheduled Task Executing Encoded Payload from Registry

Severity: high
Author: pH-T (Nextron Systems), @Kostastsale, TheDFIRReport, X__Junior (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects the creation of a schtask that potentially executes a base64 encoded payload stored in the Windows Registry using PowerShell.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1053.005` Scheduled Task/Job: Scheduled Task, `T1059.001` Command and Scripting Interpreter: PowerShell
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_cli_create`

CommandLine|contains: '/Create'

Stage 3: `all of selection_cli_encoding`

or:
CommandLine|contains: FromBase64String
CommandLine|contains: encodedcommand

Stage 4: `all of selection_cli_get`

or:
CommandLine|contains: ' gp '
CommandLine|contains: Get-ItemProperty

Stage 5: `all of selection_cli_hive`

or:
CommandLine|contains: 'HKCU:'
CommandLine|contains: HKEY_
CommandLine|contains: 'HKLM:'
CommandLine|contains: 'registry::'

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	`gp` corpus 2 (sigma 2) `/Create` corpus 4 (sigma 4) `FromBase64String` corpus 7 (sigma 7) `Get-ItemProperty` corpus 2 (sigma 2) `HKCU:` corpus 2 (sigma 2) `HKEY_` corpus 2 (sigma 2) `HKLM:` corpus 2 (sigma 2) `encodedcommand` corpus 2 (sigma 2) `registry::` corpus 2 (sigma 2)
`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_0005.