Suspicious Manipulation Of Default Accounts Via Net.EXE

Status: test
Severity: high
Log source: product windows, category process_creation
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects suspicious manipulations of default accounts such as 'administrator' and 'guest'. For example 'enable' or 'disable' accounts or change the password...etc

MITRE ATT&CK coverage

Tactic	Techniques
Collection	`T1560.001` Archive Collected Data: Archive via Utility

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: Suspicious Manipulation Of Default Accounts Via Net.EXE
id: 5b768e71-86f2-4879-b448-81061cbae951
status: test
description: Detects suspicious manipulations of default accounts such as 'administrator' and 'guest'. For example 'enable' or 'disable' accounts or change the password...etc
references:
    - https://www.trellix.com/en-sg/about/newsroom/stories/threat-labs/lockergoga-ransomware-family-used-in-targeted-attacks.html
    - https://redacted.com/blog/bianlian-ransomware-gang-gives-it-a-go/
    - https://www.microsoft.com/security/blog/2022/09/07/profiling-dev-0270-phosphorus-ransomware-operations/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-09-01
modified: 2023-02-21
tags:
    - attack.collection
    - attack.t1560.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\net.exe'
              - '\net1.exe'
        - OriginalFileName:
              - 'net.exe'
              - 'net1.exe'
    selection_user_option:
        CommandLine|contains: ' user '
    selection_username:
        CommandLine|contains:
            # Note: We need to write the full account name for cases starting with 'admin' to avoid lookups only with the user flag
            - ' Järjestelmänvalvoja ' # Finish
            - ' Rendszergazda ' # Hungarian
            - ' Администратор ' # Russian
            - ' Administrateur ' # French
            - ' Administrador ' # Portuguese (Brazil + Portugal) + Spanish
            - ' Administratör ' # Swedish
            - ' Administrator ' # English
            - ' guest '
            - ' DefaultAccount '
            # The cases below are for when an attacker requests the net command via 'cmd /c....'
            # First in double quotes
            - ' "Järjestelmänvalvoja" ' # Finish
            - ' "Rendszergazda" ' # Hungarian
            - ' "Администратор" ' # Russian
            - ' "Administrateur" ' # French
            - ' "Administrador" ' # Portuguese (Brazil + Portugal) + Spanish
            - ' "Administratör" ' # Swedish
            - ' "Administrator" ' # English
            - ' "guest" '
            - ' "DefaultAccount" '
            # Second in single quotes
            - " 'Järjestelmänvalvoja' " # Finish
            - " 'Rendszergazda' " # Hungarian
            - " 'Администратор' " # Russian
            - " 'Administrateur' " # French
            - " 'Administrador' " # Portuguese (Brazil + Portugal) + Spanish
            - " 'Administratör' " # Swedish
            - " 'Administrator' " # English
            - " 'guest' "
            - " 'DefaultAccount' "
    filter:
        CommandLine|contains|all:
            - 'guest'
            - '/active no'
    condition: all of selection_* and not filter
falsepositives:
    - Some false positives could occur with the admin or guest account. It depends on the scripts being used by the admins in your env. If you experience a lot of FP you could reduce the level to medium
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_* and not filter

Stage 1: `selection_img`

selection_img:
    - Image|endswith:
          - '\net.exe'
          - '\net1.exe'
    - OriginalFileName:
          - 'net.exe'
          - 'net1.exe'

Stage 2: `selection_user_option`

selection_user_option:
    CommandLine|contains: ' user '

Stage 3: `selection_username`

selection_username:
    CommandLine|contains:
        - ' Järjestelmänvalvoja '
        - ' Rendszergazda '
        - ' Администратор '
        - ' Administrateur '
        - ' Administrador '
        - ' Administratör '
        - ' Administrator '
        - ' guest '
        - ' DefaultAccount '
        - ' "Järjestelmänvalvoja" '
        - ' "Rendszergazda" '
        - ' "Администратор" '
        - ' "Administrateur" '
        - ' "Administrador" '
        - ' "Administratör" '
        - ' "Administrator" '
        - ' "guest" '
        - ' "DefaultAccount" '
        - " 'Järjestelmänvalvoja' "
        - " 'Rendszergazda' "
        - " 'Администратор' "
        - " 'Administrateur' "
        - " 'Administrador' "
        - " 'Administratör' "
        - " 'Administrator' "
        - " 'guest' "
        - " 'DefaultAccount' "

Stage 4: `not filter`

filter:
    CommandLine|contains|all:
        - 'guest'
        - '/active no'

Exclusions

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

Field	Kind	Excluded values
`CommandLine`	match	`/active no`
`CommandLine`	match	`guest`

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	`"Administrador"` `"Administrateur"` `"Administrator"` `"Administratör"` `"DefaultAccount"` `"Järjestelmänvalvoja"` `"Rendszergazda"` `"guest"` `"Администратор"` `'Administrador'` `'Administrateur'` `'Administrator'` `'Administratör'` `'DefaultAccount'` `'Järjestelmänvalvoja'` `'Rendszergazda'` `'guest'` `'Администратор'` `Administrador` `Administrateur` `Administrator` `Administratör` `DefaultAccount` `Järjestelmänvalvoja` `Rendszergazda` `guest` `user` corpus 3 (sigma 3) `Администратор`
`Image`	ends_with	`\net.exe` corpus 49 (sigma 49) `\net1.exe` corpus 47 (sigma 47)
`OriginalFileName`	eq	`net.exe` corpus 28 (sigma 19, elastic 7, splunk 2) `net1.exe` corpus 44 (sigma 19, splunk 19, elastic 6)

`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 Manipulation Of Default Accounts Via Net.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_user_option`

Stage 3: `selection_username`

Stage 4: `not filter`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Suspicious Manipulation Of Default Accounts Via Net.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_user_option

Stage 3: selection_username

Stage 4: not filter

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_user_option`

Stage 3: `selection_username`

Stage 4: `not filter`