WS FTP Remote Code Execution

Status: production
Severity: medium
Group by: Web.src, Web.status, Web.url_length, c-uri, c-useragent, cs-host, cs-method
Author: Michael Haag, Splunk
Source: github.com/splunk/security_content

The following analytic detects potential Remote Code Execution (RCE) attempts exploiting CVE-2023-40044 in WS_FTP software. It identifies HTTP POST requests to the "/AHT/AhtApiService.asmx/AuthUser" URL with a status code of 200. This detection leverages the Web datamodel to monitor specific URL patterns and HTTP status codes. This activity is significant as it may indicate an exploitation attempt, potentially allowing an attacker to execute arbitrary code on the server. If confirmed malicious, this could lead to unauthorized access, data exfiltration, or further compromise of the affected system.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application

Rule body splunk

name: WS FTP Remote Code Execution
id: b84e8f39-4e7b-4d4f-9e7c-fcd29a227845
version: 11
creation_date: '2023-10-01'
modification_date: '2026-05-13'
author: Michael Haag, Splunk
status: production
type: TTP
description: |-
    The following analytic detects potential Remote Code Execution (RCE) attempts exploiting CVE-2023-40044 in WS_FTP software.
    It identifies HTTP POST requests to the "/AHT/AhtApiService.asmx/AuthUser" URL with a status code of 200.
    This detection leverages the Web datamodel to monitor specific URL patterns and HTTP status codes. This activity is significant as it may indicate an exploitation attempt, potentially allowing an attacker to execute arbitrary code on the server.
    If confirmed malicious, this could lead to unauthorized access, data exfiltration, or further compromise of the affected system.
data_source:
    - Suricata
search: |-
    | tstats `security_content_summariesonly`
      count min(_time) as firstTime
            max(_time) as lastTime
    
    FROM datamodel=Web WHERE
    
    Web.url="*/AHT/AhtApiService.asmx/AuthUser"
    Web.status=200
    Web.http_method="POST"
    
    BY Web.http_user_agent Web.status Web.http_method
       Web.url Web.url_length Web.src Web.dest
    
    | `drop_dm_object_name("Web")`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `ws_ftp_remote_code_execution_filter`
how_to_implement: |-
    The following analytic requires the Web datamodel. Ensure data source is mapped correctly or modify and tune for your data source.
known_false_positives: |-
    If WS_FTP Server is not in use, this analytic will not return results. Monitor and tune for your environment.
    Note the MetaSploit module is focused on only hitting /AHT/ and not the full /AHT/AhtApiService.asmx/AuthUser URL.
references:
    - https://github.com/projectdiscovery/nuclei-templates/pull/8296/files
    - https://www.assetnote.io/resources/research/rce-in-progress-ws-ftp-ad-hoc-via-iis-http-modules-cve-2023-40044
    - https://github.com/rapid7/metasploit-framework/pull/18414
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: Potential WS FTP Remote Code Execution detected against URL $url$ on $dest$ from $src$
    entity:
        field: dest
        type: system
        score: 50
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - WS FTP Server Critical Vulnerabilities
asset_type: Web Server
cve:
    - CVE-2023-40044
mitre_attack_id:
    - T1190
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: web
security_domain: network
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1190/ws_ftp/wsftpweb.log
          source: not_applicable
          sourcetype: suricata
      test_type: unit

Stages and Predicates

Stage 1: `tstats`

| tstats `security_content_summariesonly`
  count min(_time) as firstTime
        max(_time) as lastTime

FROM datamodel=Web WHERE

Web.url="*/AHT/AhtApiService.asmx/AuthUser"
Web.status=200
Web.http_method="POST"

BY Web.http_user_agent Web.status Web.http_method
   Web.url Web.url_length Web.src Web.dest

Stage 2: `search`

| `drop_dm_object_name("Web")`

Stage 3: `search`

| `security_content_ctime(firstTime)`

Stage 4: `search`

| `security_content_ctime(lastTime)`

Stage 5: `search`

| `ws_ftp_remote_code_execution_filter`

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
`Web.http_method`	eq	`"POST"`
`Web.status`	eq	`200`
`Web.url`	eq	`"*/AHT/AhtApiService.asmx/AuthUser"`

`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)

WS FTP Remote Code Execution

MITRE ATT&CK coverage

Rule body splunk

Stages and Predicates

Stage 1: `tstats`

Stage 2: `search`

Stage 3: `search`

Stage 4: `search`

Stage 5: `search`

Indicators

Keyboard shortcuts

Search operators

WS FTP Remote Code Execution

MITRE ATT&CK coverage

Rule body splunk

Stages and Predicates

Stage 1: tstats

Stage 2: search

Stage 3: search

Stage 4: search

Stage 5: search

Indicators

Stage 1: `tstats`

Stage 2: `search`

Stage 3: `search`

Stage 4: `search`

Stage 5: `search`