Rule Category

INDICATOR-SCAN -- Snort detected a system behavior that suggests the system has been affected by malware. That behavior is known as an Indicator of Compromise (IOC). The symptoms could be a wide range of behaviors, from a suspicious file name to an unusual use of a utility. Symptoms do not guarantee an infection; your network configuration may not be affected by malware, but showing indicators as a result of a normal function. This alert showed because Snort has detected a tool or script attempting to find objects on the network. This could be as simple as pinging a specific port that WordPress admins commonly use to see if a WordPress-targeted attack might succeed, or it could be as complex as attempting to create a map of the entire network, including ports, services, and devices. Snort scans the signature of this attempt to determine if it is different from the allowed network scanning tools (such as NMAP), and is therefore likely an attack.

Alert Message

INDICATOR-SCAN CallStranger UPnP discovery attempt

Rule Explanation

The CallStranger tool scans a local network for UPNP enabled devices and checks if they are vulnerable to a SUBSCRIBER Callback data exfiltration attack.

What To Look For

This rule alerts when an attempt is made by the CallStranger tool to discovery vulnerable UPNP devices on a network.

Known Usage

Public information/Proof of Concept available

False Positives

No known false positives


Cisco Talos Intelligence Group

MITRE ATT&CK Framework

Tactic: Discovery

Technique: Network Service Scanning

For reference, see the MITRE ATT&CK vulnerability types here:

Additional Links

Rule Vulnerability


Not Applicable

CVE Additional Information