Detection: WS FTP Remote Code Execution

Updated Date: 2024-08-16 ID: b84e8f39-4e7b-4d4f-9e7c-fcd29a227845 Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

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.

Search

1
2| tstats count min(_time) as firstTime max(_time) as lastTime from datamodel=Web where Web.url IN ("/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, sourcetype 
3| `drop_dm_object_name("Web")` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `ws_ftp_remote_code_execution_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Suricata	N/A	`'suricata'`	`'suricata'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
ws_ftp_remote_code_execution_filter	`search *`

ws_ftp_remote_code_execution_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1190	Exploit Public-Facing Application	Initial Access

KillChainPhase.DELIVERY

NistCategory.DE_CM

Cis18Value.CIS_13

APT28

APT29

APT39

APT41

APT5

Axiom

BackdoorDiplomacy

BlackTech

Blue Mockingbird

Cinnamon Tempest

Dragonfly

Earth Lusca

FIN13

FIN7

Fox Kitten

GALLIUM

GOLD SOUTHFIELD

HAFNIUM

Ke3chang

Kimsuky

Magic Hound

Moses Staff

MuddyWater

Rocke

Sandworm Team

Threat Group-3390

ToddyCat

Volatile Cedar

Volt Typhoon

menuPass

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

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.

Associated Analytic Story

WS FTP Server Critical Vulnerabilities

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Potential WS FTP Remote Code Execution detected against URL $url$ on $dest$ from $src$	72	90	80

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`suricata`	`suricata`
Integration	✅ Passing	Dataset	`suricata`	`suricata`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 3