Suspicious SYSTEM User Process Creation

Status: test
Severity: high
Log source: product windows, category process_creation
Author: Florian Roth (Nextron Systems), David ANDRE (additional keywords)
Source: github.com/SigmaHQ/sigma

Detects a suspicious process creation as SYSTEM user (suspicious program or command line parameter)

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1134` Access Token Manipulation
Stealth	`T1027` Obfuscated Files or Information, `T1134` Access Token Manipulation
Credential Access	`T1003` OS Credential Dumping

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: Suspicious SYSTEM User Process Creation
id: 2617e7ed-adb7-40ba-b0f3-8f9945fe6c09
status: test
description: Detects a suspicious process creation as SYSTEM user (suspicious program or command line parameter)
references:
    - Internal Research
    - https://tools.thehacker.recipes/mimikatz/modules
author: Florian Roth (Nextron Systems), David ANDRE (additional keywords)
date: 2021-12-20
modified: 2025-10-19
tags:
    - attack.credential-access
    - attack.privilege-escalation
    - attack.stealth
    - attack.t1134
    - attack.t1003
    - attack.t1027
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        IntegrityLevel:
            - 'System'
            - 'S-1-16-16384'
        User|contains: # covers many language settings
            - 'AUTHORI'
            - 'AUTORI'
    selection_special:
        - Image|endswith:
              - '\calc.exe'
              - '\cscript.exe'
              - '\forfiles.exe'
              - '\hh.exe'
              - '\mshta.exe'
              - '\ping.exe'
              - '\wscript.exe'
        - CommandLine|re: 'net\s+user\s+'
        - CommandLine|contains:
              # - 'sc stop ' # stops a system service # causes FPs
              - ' -NoP '  # Often used in malicious PowerShell commands
              - ' -W Hidden '  # Often used in malicious PowerShell commands
              - ' -decode '  # Used with certutil
              - ' /decode '  # Used with certutil
              - ' /urlcache '  # Used with certutil
              - ' -urlcache '  # Used with certutil
              - ' -e* JAB'  # PowerShell encoded commands
              - ' -e* SUVYI'  # PowerShell encoded commands
              - ' -e* SQBFAFgA'  # PowerShell encoded commands
              - ' -e* aWV4I'  # PowerShell encoded commands
              - ' -e* IAB'  # PowerShell encoded commands
              - ' -e* PAA'  # PowerShell encoded commands
              - ' -e* aQBlAHgA'  # PowerShell encoded commands
              - 'vssadmin delete shadows'  # Ransomware
              - 'reg SAVE HKLM'  # save registry SAM - syskey extraction
              - ' -ma '  # ProcDump
              - 'Microsoft\Windows\CurrentVersion\Run'  # Run key in command line - often in combination with REG ADD
              - '.downloadstring('  # PowerShell download command
              - '.downloadfile('  # PowerShell download command
              - ' /ticket:'  # Rubeus
              - 'dpapi::'     # Mimikatz
              - 'event::clear'        # Mimikatz
              - 'event::drop'     # Mimikatz
              - 'id::modify'      # Mimikatz
              - 'kerberos::'       # Mimikatz
              - 'lsadump::'      # Mimikatz
              - 'misc::'     # Mimikatz
              - 'privilege::'       # Mimikatz
              - 'rpc::'      # Mimikatz
              - 'sekurlsa::'       # Mimikatz
              - 'sid::'        # Mimikatz
              - 'token::'      # Mimikatz
              - 'vault::cred'     # Mimikatz
              - 'vault::list'     # Mimikatz
              - ' p::d '  # Mimikatz
              - ';iex('  # PowerShell IEX
              - 'MiniDump'  # Process dumping method apart from procdump
    filter_main_ping:
        CommandLine|contains|all:
            - 'ping'
            - '127.0.0.1'
            - ' -n '
    filter_vs:
        Image|endswith: '\PING.EXE'
        ParentCommandLine|contains: '\DismFoDInstall.cmd'
    filter_config_mgr:
        ParentImage|contains: ':\Packages\Plugins\Microsoft.GuestConfiguration.ConfigurationforWindows\'
    filter_java:
        ParentImage|contains:
            - ':\Program Files (x86)\Java\'
            - ':\Program Files\Java\'
        ParentImage|endswith: '\bin\javaws.exe'
        Image|contains:
            - ':\Program Files (x86)\Java\'
            - ':\Program Files\Java\'
        Image|endswith: '\bin\jp2launcher.exe'
        CommandLine|contains: ' -ma '
    condition: all of selection* and not 1 of filter_*
falsepositives:
    - Administrative activity
    - Scripts and administrative tools used in the monitored environment
    - Monitoring activity
level: high

Stages and Predicates

Stage 0: `condition`

all of selection* and not 1 of filter_*

Stage 1: `selection`

selection:
    IntegrityLevel:
        - 'System'
        - 'S-1-16-16384'
    User|contains:
        - 'AUTHORI'
        - 'AUTORI'

Stage 2: `selection_special`

selection_special:
    - Image|endswith:
          - '\calc.exe'
          - '\cscript.exe'
          - '\forfiles.exe'
          - '\hh.exe'
          - '\mshta.exe'
          - '\ping.exe'
          - '\wscript.exe'
    - CommandLine|re: 'net\s+user\s+'
    - CommandLine|contains:
          - ' -NoP '
          - ' -W Hidden '
          - ' -decode '
          - ' /decode '
          - ' /urlcache '
          - ' -urlcache '
          - ' -e* JAB'
          - ' -e* SUVYI'
          - ' -e* SQBFAFgA'
          - ' -e* aWV4I'
          - ' -e* IAB'
          - ' -e* PAA'
          - ' -e* aQBlAHgA'
          - 'vssadmin delete shadows'
          - 'reg SAVE HKLM'
          - ' -ma '
          - 'Microsoft\Windows\CurrentVersion\Run'
          - '.downloadstring('
          - '.downloadfile('
          - ' /ticket:'
          - 'dpapi::'
          - 'event::clear'
          - 'event::drop'
          - 'id::modify'
          - 'kerberos::'
          - 'lsadump::'
          - 'misc::'
          - 'privilege::'
          - 'rpc::'
          - 'sekurlsa::'
          - 'sid::'
          - 'token::'
          - 'vault::cred'
          - 'vault::list'
          - ' p::d '
          - ';iex('
          - 'MiniDump'

Stage 3: `not filter_*`

filter_main_ping:
    CommandLine|contains|all:
        - 'ping'
        - '127.0.0.1'
        - ' -n '
filter_vs:
    Image|endswith: '\PING.EXE'
    ParentCommandLine|contains: '\DismFoDInstall.cmd'
filter_config_mgr:
    ParentImage|contains: ':\Packages\Plugins\Microsoft.GuestConfiguration.ConfigurationforWindows\'
filter_java:
    ParentImage|contains:
        - ':\Program Files (x86)\Java\'
        - ':\Program Files\Java\'
    ParentImage|endswith: '\bin\javaws.exe'
    Image|contains:
        - ':\Program Files (x86)\Java\'
        - ':\Program Files\Java\'
    Image|endswith: '\bin\jp2launcher.exe'
    CommandLine|contains: ' -ma '

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`Image`	match	`:\Program Files (x86)\Java\`
`Image`	match	`:\Program Files\Java\`
`ParentImage`	match	`:\Program Files (x86)\Java\`
`ParentImage`	match	`:\Program Files\Java\`
`CommandLine`	match	`-ma`
`Image`	ends_with	`\bin\jp2launcher.exe`
`ParentImage`	ends_with	`\bin\javaws.exe`
`CommandLine`	match	`-n`
`CommandLine`	match	`127.0.0.1`
`CommandLine`	match	`ping`
`Image`	ends_with	`\PING.EXE`
`ParentCommandLine`	match	`\DismFoDInstall.cmd`
`ParentImage`	match	`:\Packages\Plugins\Microsoft.GuestConfiguration.ConfigurationforWindows\`

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	`-NoP` corpus 3 (sigma 3) `-W Hidden` corpus 5 (sigma 5) `-decode` corpus 4 (sigma 4) `-e* IAB` `-e* JAB` `-e* PAA` corpus 2 (sigma 2) `-e* SQBFAFgA` `-e* SUVYI` `-e* aQBlAHgA` `-e* aWV4I` `-ma` corpus 5 (sigma 4, chronicle 1) `-urlcache` `/decode` corpus 2 (sigma 2) `/ticket:` corpus 2 (sigma 2) `/urlcache` `p::d` `.downloadfile(` corpus 8 (sigma 7, chronicle 1) `.downloadstring(` corpus 8 (sigma 7, chronicle 1) `;iex(` `Microsoft\Windows\CurrentVersion\Run` corpus 2 (sigma 2) `MiniDump` corpus 5 (sigma 4, chronicle 1) `dpapi::` corpus 3 (sigma 2, chronicle 1) `event::clear` `event::drop` `id::modify` `kerberos::` corpus 3 (sigma 2, chronicle 1) `lsadump::` corpus 3 (sigma 2, chronicle 1) `misc::` `privilege::` corpus 3 (sigma 2, chronicle 1) `reg SAVE HKLM` `rpc::` corpus 3 (sigma 2, chronicle 1) `sekurlsa::` corpus 3 (sigma 2, chronicle 1) `sid::` `token::` corpus 3 (sigma 2, chronicle 1) `vault::cred` `vault::list` `vssadmin delete shadows`
`CommandLine`	regex_match	`net\s+user\s+`
`Image`	ends_with	`\calc.exe` corpus 13 (sigma 13) `\cscript.exe` corpus 73 (sigma 73) `\forfiles.exe` corpus 12 (sigma 12) `\hh.exe` corpus 16 (sigma 16) `\mshta.exe` corpus 67 (sigma 67) `\ping.exe` corpus 7 (sigma 7) `\wscript.exe` corpus 75 (sigma 75)
`IntegrityLevel`	eq	`S-1-16-16384` corpus 29 (sigma 22, splunk 4, elastic 3) `System` corpus 29 (sigma 22, splunk 4, elastic 3)
`User`	match	`AUTHORI` corpus 14 (sigma 14) `AUTORI` corpus 14 (sigma 14)

`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)

Suspicious SYSTEM User Process Creation

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `selection_special`

Stage 3: `not filter_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Suspicious SYSTEM User Process Creation

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: selection_special

Stage 3: not filter_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `selection_special`

Stage 3: `not filter_*`