Elevated System Shell Spawned From Uncommon Parent Location

Severity: medium
Author: frack113, Tim Shelton (update fp)
Source: upstream

Detects when a shell program such as the Windows command prompt or PowerShell is launched with system privileges from a uncommon parent location.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059` Command and Scripting Interpreter

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_shell`

or:
Image|endswith: '\cmd.exe'
Image|endswith: '\powershell.exe'
Image|endswith: '\powershell_ise.exe'
Image|endswith: '\pwsh.exe'
OriginalFileName: Cmd.Exe
OriginalFileName: PowerShell.EXE
OriginalFileName: powershell_ise.EXE
OriginalFileName: pwsh.dll

Stage 2: `all of selection_user`

or:
User|contains: AUTHORI
User|contains: AUTORI
LogonId: 0x3e7

Stage 3: `not 1 of filter_main_*`

or:
ParentImage: ''
ParentImage: -
ParentImage: null
ParentImage|contains: ':\Program Files (x86)\'
ParentImage|contains: ':\Program Files\'
ParentImage|contains: ':\ProgramData\'
ParentImage|contains: ':\Windows\SysWOW64\'
ParentImage|contains: ':\Windows\System32\'
ParentImage|contains: ':\Windows\Temp\'
ParentImage|contains: ':\Windows\WinSxS\'

Stage 4: `not 1 of filter_optional_*`

or:
CommandLine|contains: ':\IBM\SpectrumProtect\webserver\scripts\'
ParentImage|contains: ':\IBM\SpectrumProtect\webserver\scripts\'
CommandLine|contains: ':\WINDOWS\system32\cmd.exe /c "'
CurrentDirectory|contains: ':\WINDOWS\Temp\asgard2-agent\'
Image|endswith: '\cmd.exe'
ParentImage|endswith: ':\ManageEngine\ADManager Plus\pgsql\bin\postgres.exe'

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	`:\IBM\SpectrumProtect\webserver\scripts\` `:\WINDOWS\system32\cmd.exe /c "`
`CurrentDirectory`	match	`:\WINDOWS\Temp\asgard2-agent\`
`Image`	ends_with	`\cmd.exe` corpus 92 (sigma 92) `\powershell.exe` corpus 143 (sigma 143) `\powershell_ise.exe` corpus 27 (sigma 27) `\pwsh.exe` corpus 140 (sigma 140)
`LogonId`	eq	`0x3e7` corpus 2 (sigma 2)
`OriginalFileName`	eq	`Cmd.Exe` corpus 32 (sigma 30, splunk 2) `PowerShell.EXE` corpus 64 (sigma 60, splunk 4) `powershell_ise.EXE` corpus 8 (sigma 4, splunk 4) `pwsh.dll` corpus 72 (sigma 68, splunk 4)
`ParentImage`	ends_with	`:\ManageEngine\ADManager Plus\pgsql\bin\postgres.exe`
`ParentImage`	eq	`-` corpus 5 (sigma 5)
`ParentImage`	match	`:\IBM\SpectrumProtect\webserver\scripts\` `:\Program Files (x86)\` `:\Program Files\` `:\ProgramData\` `:\Windows\SysWOW64\` corpus 2 (sigma 2) `:\Windows\System32\` corpus 2 (sigma 2) `:\Windows\Temp\` corpus 4 (sigma 4) `:\Windows\WinSxS\`
`User`	match	`AUTHORI` corpus 16 (sigma 16) `AUTORI` corpus 16 (sigma 16)

Elevated System Shell Spawned From Uncommon Parent Location

MITRE ATT&CK coverage

Event coverage

Stages and Predicates

Stage 1: all of selection_shell

Stage 2: all of selection_user

Stage 3: not 1 of filter_main_*

Stage 4: not 1 of filter_optional_*

Indicators

Stage 1: `all of selection_shell`

Stage 2: `all of selection_user`

Stage 3: `not 1 of filter_main_*`

Stage 4: `not 1 of filter_optional_*`