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MODBUS Function Code Scan

 
Signature ID: 36686/0
Original Release:S604
Release:S604 (download)
Original Release Date:2011 October 24
Latest Release Date:2011 October 24
Default Enabled:False
Default Retired:True
Alarm Severity:Low
Fidelity:90 

Description

When the function code received in a MODBUS request is not supported by a slave device, the device generates an Exception response with an exception code of 0x01. Frequent Invalid Function Exception responses can indicate attempted reconnaissance of the device.This signature will alert if 3 exception responses are seen in a short period time between the same devices.You are entitled to use this signature only if you have purchased an IPS SCADA Signature License.

Recommended Filter

There are no suggested filters.

Benign Triggers

A possible benign trigger is when a MODBUS master is mis-configured or designed to use functionality not supported by a particular device queries the slave for the unsupported function code at a high frequency.

IntelliShield Alerts

IntelliShield ID Headline VersionCVSS ScoreLast Published
23280MODBUS/TCP Protocol Multiple Protocol Implementation Vulnerabilities12011 October 25 14:45 GMT

Download

To download this and other IPS update files, please go to Cisco Secure Software Download.

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