Suspicious External WebDAV Execution

Status: test
Severity: high
Log source: category proxy
Author: Ahmed Farouk
Source: github.com/SigmaHQ/sigma

Detects executables launched from external WebDAV shares using the WebDAV Explorer integration, commonly seen in initial access campaigns.

MITRE ATT&CK coverage

Tactic	Techniques
Resource Development	`T1584` Compromise Infrastructure
Initial Access	`T1566` Phishing

Rule body yaml

title: Suspicious External WebDAV Execution
id: 1ae64f96-72b6-48b3-ad3d-e71dff6c6398
related:
    - id: 4c55738d-72d8-490e-a2db-7969654e375f
      type: similar
status: test
description: |
    Detects executables launched from external WebDAV shares using the WebDAV Explorer integration, commonly seen in initial access campaigns.
references:
    - https://dear-territory-023.notion.site/WebDav-Share-Testing-e4950fa0c00149c3aa430d779b9b1d0f?pvs=4
    - https://micahbabinski.medium.com/search-ms-webdav-and-chill-99c5b23ac462
    - https://www.trendmicro.com/en_no/research/24/b/cve202421412-water-hydra-targets-traders-with-windows-defender-s.html
    - https://www.trellix.com/en-us/about/newsroom/stories/research/beyond-file-search-a-novel-method.html
author: Ahmed Farouk
date: 2024-05-10
tags:
    - attack.initial-access
    - attack.resource-development
    - attack.t1584
    - attack.t1566
logsource:
    category: proxy
detection:
    selection_webdav:
        c-useragent|startswith: 'Microsoft-WebDAV-MiniRedir/'
        cs-method: 'GET'
    selection_execution:
        c-uri|endswith:
            - '.7z'
            - '.bat'
            - '.dat'
            - '.cmd'
            - '.exe'
            - '.js'
            - '.lnk'
            - '.ps1'
            - '.rar'
            - '.url'
            - '.vbe'
            - '.vbs'
            - '.zip'
    filter_main_local_ips:
        dst_ip|cidr:
            - '127.0.0.0/8'
            - '10.0.0.0/8'
            - '172.16.0.0/12'
            - '192.168.0.0/16'
            - '169.254.0.0/16'
            - '::1/128'  # IPv6 loopback
            - 'fe80::/10'  # IPv6 link-local addresses
            - 'fc00::/7'  # IPv6 private addresses
    condition: all of selection_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_* and not 1 of filter_main_*

Stage 1: `selection_webdav`

selection_webdav:
    c-useragent|startswith: 'Microsoft-WebDAV-MiniRedir/'
    cs-method: 'GET'

Stage 2: `selection_execution`

selection_execution:
    c-uri|endswith:
        - '.7z'
        - '.bat'
        - '.dat'
        - '.cmd'
        - '.exe'
        - '.js'
        - '.lnk'
        - '.ps1'
        - '.rar'
        - '.url'
        - '.vbe'
        - '.vbs'
        - '.zip'

Stage 3: `not filter_main_local_ips`

filter_main_local_ips:
    dst_ip|cidr:
        - '127.0.0.0/8'
        - '10.0.0.0/8'
        - '172.16.0.0/12'
        - '192.168.0.0/16'
        - '169.254.0.0/16'
        - '::1/128'
        - 'fe80::/10'
        - 'fc00::/7'

Exclusions

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

Field	Kind	Excluded values
`dst_ip`	cidr_match	`10.0.0.0/8`
`dst_ip`	cidr_match	`127.0.0.0/8`
`dst_ip`	cidr_match	`169.254.0.0/16`
`dst_ip`	cidr_match	`172.16.0.0/12`
`dst_ip`	cidr_match	`192.168.0.0/16`
`dst_ip`	cidr_match	`::1/128`
`dst_ip`	cidr_match	`fc00::/7`
`dst_ip`	cidr_match	`fe80::/10`

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
`c-uri`	ends_with	`.7z` `.bat` `.cmd` `.dat` `.exe` `.js` `.lnk` `.ps1` `.rar` `.url` `.vbe` `.vbs` `.zip`
`c-useragent`	starts_with	`Microsoft-WebDAV-MiniRedir/`
`cs-method`	eq	`GET`

`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 External WebDAV Execution

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_webdav`

Stage 2: `selection_execution`

Stage 3: `not filter_main_local_ips`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Suspicious External WebDAV Execution

MITRE ATT&CK coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_webdav

Stage 2: selection_execution

Stage 3: not filter_main_local_ips

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_webdav`

Stage 2: `selection_execution`

Stage 3: `not filter_main_local_ips`