Detection: PaperCut NG Remote Web Access Attempt

Updated Date: 2026-05-13 ID: 9fcb214a-dc42-4ce7-a650-f1d2cab16a6a Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects potential exploitation attempts on publicly accessible PaperCut NG servers. It identifies connections from public IP addresses to the server, specifically monitoring URI paths commonly used in proof-of-concept scripts for exploiting PaperCut NG vulnerabilities. This detection leverages web traffic data from the Web datamodel, focusing on specific URI paths and excluding internal IP ranges. This activity is significant as it may indicate an attempt to exploit known vulnerabilities in PaperCut NG, potentially leading to unauthorized access or control of the server. If confirmed malicious, attackers could gain administrative access, leading to data breaches or further network compromise.

Search

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5
 6from datamodel=Web WHERE
 7
 8Web.url IN (
 9  "*/app?service=direct/1/PrinterDetails/printerOptionsTab.tab"
10  "*/app?service=direct/1/PrinterList/selectPrinter&sp=*",
11  "*/app?service=page/PrinterList",
12  "*/app?service=page/SetupCompleted"
13)
14NOT src IN (
15              "10.0.0.0/8",
16              "172.16.0.0/12",
17              "192.168.0.0/16",
18              "100.64.0.0/10",
19              "127.0.0.0/8",
20              "169.254.0.0/16",
21              "192.0.0.0/24",
22              "192.0.0.0/29",
23              "192.0.0.8/32",
24              "192.0.0.9/32",
25              "192.0.0.10/32",
26              "192.0.0.170/32",
27              "192.0.0.171/32",
28              "192.0.2.0/24",
29              "192.31.196.0/24",
30              "192.52.193.0/24",
31              "192.88.99.0/24",
32              "224.0.0.0/4",
33              "192.175.48.0/24",
34              "198.18.0.0/15",
35              "198.51.100.0/24",
36              "203.0.113.0/24",
37              "240.0.0.0/4",
38              "::1"
39            )
40by Web.http_user_agent Web.http_method
41   Web.url,Web.url_length Web.src
42   Web.dest Web.dest_port
43
44
45| `drop_dm_object_name("Web")`
46
47| `security_content_ctime(firstTime)`
48
49| `security_content_ctime(lastTime)`
50
51| `papercut_ng_remote_web_access_attempt_filter`

Data Source

Name	Platform	Sourcetype	Source
Suricata	Other	`'suricata'`	`'not_applicable'`

Macros Used

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

papercut_ng_remote_web_access_attempt_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
T1133	External Remote Services	Initial Access
T1190	Exploit Public-Facing Application	Persistence

Installation

Delivery

DE.CM

CIS 13

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 Finding (Notable)	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Intermediate Finding (Risk Event)	No

TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

Implementation

To successfully implement this search you need to be ingesting information on Web traffic that include fields relevant for traffic into the Web datamodel.

Known False Positives

False positives may be present if you allow access to the PaperCut NG server from public IP addresses. Filter as needed.

Associated Analytic Story

PaperCut MF NG Vulnerability

Finding

Title	Entity Field	Entity Type	Risk Score
URIs specific to PaperCut NG have been access by a public IP $src$ against $dest$.	dest	system	50

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`not_applicable`	`suricata`
Integration	✅ Passing	Dataset	`not_applicable`	`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: 10