Set Suspicious Files as System Files Using Attrib.EXE

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

Detects the usage of attrib with the "+s" option to set scripts or executables located in suspicious locations as system files to hide them from users and make them unable to be deleted with simple rights. The rule limits the search to specific extensions and directories to avoid FPs

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1564.001` Hide Artifacts: Hidden Files and Directories

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: Set Suspicious Files as System Files Using Attrib.EXE
id: efec536f-72e8-4656-8960-5e85d091345b
related:
    - id: bb19e94c-59ae-4c15-8c12-c563d23fe52b
      type: derived
status: test
description: |
    Detects the usage of attrib with the "+s" option to set scripts or executables located in suspicious locations as system files to hide them from users and make them unable to be deleted with simple rights. The rule limits the search to specific extensions and directories to avoid FPs
references:
    - https://app.any.run/tasks/c28cabc8-a19f-40f3-a78b-cae506a5c0d4
    - https://app.any.run/tasks/cfc8870b-ccd7-4210-88cf-a8087476a6d0
    - https://unit42.paloaltonetworks.com/unit42-sure-ill-take-new-combojack-malware-alters-clipboards-steal-cryptocurrency/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-06-28
modified: 2023-03-14
tags:
    - attack.stealth
    - attack.t1564.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\attrib.exe'
        - OriginalFileName: 'ATTRIB.EXE'
    selection_cli:
        CommandLine|contains: ' +s'
    selection_paths:
        CommandLine|contains:
            - ' %' # Custom Environment variable
            - '\Users\Public\'
            - '\AppData\Local\'
            - '\ProgramData\'
            - '\Downloads\'
            - '\Windows\Temp\'
    selection_ext:
        CommandLine|contains:
            - '.bat'
            - '.dll'
            - '.exe'
            - '.hta'
            - '.ps1'
            - '.vbe'
            - '.vbs'
    filter_optional_installer:
        CommandLine|contains|all:
            - '\Windows\TEMP\'
            - '.exe'
    condition: all of selection* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

all of selection* and not 1 of filter_optional_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\attrib.exe'
    - OriginalFileName: 'ATTRIB.EXE'

Stage 2: `selection_cli`

selection_cli:
    CommandLine|contains: ' +s'

Stage 3: `selection_paths`

selection_paths:
    CommandLine|contains:
        - ' %'
        - '\Users\Public\'
        - '\AppData\Local\'
        - '\ProgramData\'
        - '\Downloads\'
        - '\Windows\Temp\'

Stage 4: `selection_ext`

selection_ext:
    CommandLine|contains:
        - '.bat'
        - '.dll'
        - '.exe'
        - '.hta'
        - '.ps1'
        - '.vbe'
        - '.vbs'

Stage 5: `not filter_optional_installer`

filter_optional_installer:
    CommandLine|contains|all:
        - '\Windows\TEMP\'
        - '.exe'

Exclusions

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

Field	Kind	Excluded values
`CommandLine`	match	`.exe`
`CommandLine`	match	`\Windows\TEMP\`

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	`%` `+s` `.bat` corpus 11 (sigma 9, elastic 1, kusto 1) `.dll` corpus 16 (sigma 16) `.exe` corpus 5 (sigma 5) `.hta` corpus 6 (sigma 6) `.ps1` corpus 4 (sigma 3, elastic 1) `.vbe` corpus 5 (sigma 5) `.vbs` corpus 7 (sigma 7) `\AppData\Local\` corpus 10 (sigma 10) `\Downloads\` corpus 14 (sigma 14) `\ProgramData\` corpus 3 (sigma 3) `\Users\Public\` corpus 17 (sigma 17) `\Windows\Temp\` corpus 12 (sigma 12)
`Image`	ends_with	`\attrib.exe` corpus 5 (sigma 5)
`OriginalFileName`	eq	`ATTRIB.EXE` corpus 5 (sigma 3, elastic 2)

`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)

Set Suspicious Files as System Files Using Attrib.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_cli`

Stage 3: `selection_paths`

Stage 4: `selection_ext`

Stage 5: `not filter_optional_installer`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Set Suspicious Files as System Files Using Attrib.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_cli

Stage 3: selection_paths

Stage 4: selection_ext

Stage 5: not filter_optional_installer

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_cli`

Stage 3: `selection_paths`

Stage 4: `selection_ext`

Stage 5: `not filter_optional_installer`