File With Suspicious Extension Downloaded Via Bitsadmin

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

Detects usage of bitsadmin downloading a file with a suspicious extension

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1197` BITS Jobs
Persistence	`T1197` BITS Jobs
Stealth	`T1036.003` Masquerading: Rename Legitimate Utilities, `T1197` BITS Jobs
Command & Control	`T1105` Ingress Tool Transfer

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: File With Suspicious Extension Downloaded Via Bitsadmin
id: 5b80a791-ad9b-4b75-bcc1-ad4e1e89c200
status: test
description: Detects usage of bitsadmin downloading a file with a suspicious extension
references:
    - https://blog.netspi.com/15-ways-to-download-a-file/#bitsadmin
    - https://isc.sans.edu/diary/22264
    - https://lolbas-project.github.io/lolbas/Binaries/Bitsadmin/
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
date: 2022-06-28
modified: 2023-05-30
tags:
    - attack.persistence
    - attack.execution
    - attack.stealth
    - attack.t1197
    - attack.s0190
    - attack.t1036.003
    - attack.command-and-control
    - attack.t1105
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\bitsadmin.exe'
        - OriginalFileName: 'bitsadmin.exe'
    selection_flags:
        CommandLine|contains:
            - ' /transfer '
            - ' /create '
            - ' /addfile '
    selection_extension:
        CommandLine|contains:
            - '.7z'
            - '.asax'
            - '.ashx'
            - '.asmx'
            - '.asp'
            - '.aspx'
            - '.bat'
            - '.cfm'
            - '.cgi'
            - '.chm'
            - '.cmd'
            - '.dll'
            - '.gif'
            - '.jpeg'
            - '.jpg'
            - '.jsp'
            - '.jspx'
            - '.log'
            - '.png'
            - '.ps1'
            - '.psm1'
            - '.rar'
            - '.scf'
            - '.sct'
            - '.txt'
            - '.vbe'
            - '.vbs'
            - '.war'
            - '.wsf'
            - '.wsh'
            - '.xll'
            - '.zip'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_bitsadmin_download_susp_extensions/info.yml
simulation:
    - type: atomic-red-team
      name: Windows - BITSAdmin BITS Download
      technique: T1105
      atomic_guid: a1921cd3-9a2d-47d5-a891-f1d0f2a7a31b

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\bitsadmin.exe'
    - OriginalFileName: 'bitsadmin.exe'

Stage 2: `selection_flags`

selection_flags:
    CommandLine|contains:
        - ' /transfer '
        - ' /create '
        - ' /addfile '

Stage 3: `selection_extension`

selection_extension:
    CommandLine|contains:
        - '.7z'
        - '.asax'
        - '.ashx'
        - '.asmx'
        - '.asp'
        - '.aspx'
        - '.bat'
        - '.cfm'
        - '.cgi'
        - '.chm'
        - '.cmd'
        - '.dll'
        - '.gif'
        - '.jpeg'
        - '.jpg'
        - '.jsp'
        - '.jspx'
        - '.log'
        - '.png'
        - '.ps1'
        - '.psm1'
        - '.rar'
        - '.scf'
        - '.sct'
        - '.txt'
        - '.vbe'
        - '.vbs'
        - '.war'
        - '.wsf'
        - '.wsh'
        - '.xll'
        - '.zip'

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	`/addfile` corpus 5 (sigma 5) `/create` corpus 15 (sigma 15) `/transfer` corpus 5 (sigma 5) `.7z` corpus 2 (sigma 2) `.asax` `.ashx` `.asmx` `.asp` `.aspx` corpus 2 (sigma 2) `.bat` corpus 11 (sigma 9, elastic 1, kusto 1) `.cfm` `.cgi` `.chm` corpus 2 (sigma 2) `.cmd` corpus 6 (sigma 5, elastic 1) `.dll` corpus 16 (sigma 16) `.gif` corpus 8 (sigma 8) `.jpeg` corpus 6 (sigma 6) `.jpg` corpus 7 (sigma 7) `.jsp` corpus 2 (sigma 2) `.jspx` `.log` corpus 4 (sigma 4) `.png` corpus 7 (sigma 7) `.ps1` corpus 4 (sigma 3, elastic 1) `.psm1` `.rar` corpus 2 (sigma 2) `.scf` `.sct` `.txt` corpus 9 (sigma 9) `.vbe` corpus 5 (sigma 5) `.vbs` corpus 7 (sigma 7) `.war` `.wsf` corpus 4 (sigma 3, elastic 1) `.wsh` corpus 4 (sigma 4) `.xll` `.zip` corpus 6 (sigma 5, chronicle 1)
`Image`	ends_with	`\bitsadmin.exe` corpus 29 (sigma 29)
`OriginalFileName`	eq	`bitsadmin.exe` corpus 12 (sigma 9, splunk 2, kusto 1)

`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)

File With Suspicious Extension Downloaded Via Bitsadmin

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_flags`

Stage 3: `selection_extension`

Indicators

Keyboard shortcuts

Search operators

File With Suspicious Extension Downloaded Via Bitsadmin

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_flags

Stage 3: selection_extension

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_flags`

Stage 3: `selection_extension`