Categories Overview

Categories Overview

About Lenovo NetFilter Categories

Lenovo NetFilter has many different types of categories.  Some of these categories are available for blocking, while others are only available for reporting purposes. 

How Category Filtering Works

Category filtering is the sorting of URLs into subject categories for subsequent filtering based on that subject content. Lenovo NetFilter’s Categorization Engine scans and sorts the content of billions of websites and adds this information to a database of categorized sites maintained on the Lenovo NetFilter Category Name Server (CNS). This is periodically downloaded to local Lenovo NetFilter Policy Servers.

This example shows five URLs.  Each URL has been categorized by Lenovo NetFilter.  Based on these Categories, the URLs can be allowed or denied.

If a URL is denied, a Deny Page will be served.

Viewing Category Definitions

You can view the Categories used in your Lenovo NetFilter implementation by going to URL Tools> Category Lookup and clicking the Category Definitions tab. Category Definitions contains Lenovo NetFilter’s official definitions of what type of content a URL must contain to be included into each of the available categories.

Beside the category name you will see a view of the category.  Additionally, if you create a new category, it will also display in this page.  See the 'Category Manager' for more information on Custom Categories.

Default Category Groupings

The default Lenovo NetFilter Category parent groups are listed below. Each Category group contains a list sub-categories and categories.

Category Main Groups



This can be used to block websites from specific countries.

Mobile Apps

This is the parent category group for commonly accessed Mobile Applications which includes Real Gambling Apps.


nMonitor safeguarding categories


This is the parent category group for commonly accessed Internet Protocols.


This group includes sub-groups and Categories not determined by the page content.

Web Apps

This is the parent category group for commonly accessed Web Applications.

Web Content

This is the parent category group for Web based HTTP and HTTPS content.

Other Formats

You can also view Category Definitions in other formats such as HTML, XML and XMLv2.

HTML Format

The HTML Format link in the 'Other Format' section displays the Category Groups in an HTML format.  There are links that allow you to sort by name and sort by number.

XML Format

Clicking the XML link in the 'Other Format' section displays all the Category Groups.  There are links on the page that allow you to sort by Category name or sort by Category number.

Using Arguments with XML

You can also add groupnames= argument as shown below.

This example displays the Information Category Group definitions.

You can display multiple Category Groups by separating the groupnames with a comma as in the example below.  This will display Adult and Protocol Category Groups.,Protocols

Hierarchy and Classic View

There are two views: the ‘Classic View’ which is similar to previous releases and the ‘Hierarchy View’.

Hierarchy View

The ‘Hierarchy View’ displays a hierarchy of the different Category groups. 

Use the ‘Category Filter’ box to quickly search for a Category.

Classic View

You can sort the definitions by name, number, view or group. If you are looking for a particular category, you can search the list.

Category Views – WebAdmin or Reporter

You can designate that a Category can be viewable in either the WebAdmin or the Reporter.




The category will only be displayed in the WebAdmin. Reporting is not possible with this category.


The category will be displayed only in the Reporter. You will not be able to block this specific category in the WebAdmin.

WebAdmin and Reporter

The category will be displayed in both the WebAdmin and the Reporter.

Category Classification

This section contains some Category classifications that should be understood.

The General Category

The General Category is an important category to understand.  Content that is evaluated by the Lenovo NetFilter Categorization Service (CNS), will be assigned a category based on the nature of the content.  In the event that content is analyzed, and does not clearly fall into a specific subject category, it will be placed into the General category.

Content found in the General category is NOT content that has not been categorized, rather it is content that is deemed to be general in nature, not offensive, and not easily grouped into any other category.

The General Category is sometimes confused with the 'New URL' Category, but is not in any way related to the New URL category, aside from its use as a Lenovo NetFilter category for managing policy, logging, and reporting.

The New URL Category

The New URL category represents content that has not been 'seen' by your Lenovo NetFilter server, and possibly not seen by the upstream Netfilter Categorization Service. 

The New URL Category is assigned when the CNS network does not have a category for this request. In this scenario, the categorization engine will need to download and categorize the URL. You will need to make more requests to the CNS network to determine the category of the URL. Once the categorization engine has categorized this URL, a specific category will be returned. Usually, if you encounter the New URL category for a URL, this will be temporary, only until the content is categorized. New URL is very important to keep in mind when you are setting up new Lenovo NetFilter solutions.  A new Lenovo NetFilter server will have an empty URL cache, which means that many URL’s requested through the system will return New URL until the cache on the system has been populated with common URL’s that users are requesting, along with their categories.

This category is attached to a URL categorization temporarily and indicates a few different states when combined with either the Network Timeout, Network Busy or when New URL is the only category assigned to the URL.

·       New URL, Network Timeout: The CNS network did not respond quickly enough to the local filtering system before a decision needed to be made.  This categorization is a temporary state.

·       New URL, Network Busy:  The local filtering system did not have enough resources to connect to the CNS network and perform the operation. It will try again.

Blocking the New URL Category will block all website requests where the filtering system does not know the specific category of content.  It is recommended in this case the deny page automatically refreshed every few seconds until the URL is categorized and the local filtering system is aware of the category.

Advanced and System Categories

The advanced group of categories contains categorizations that are not related to the content of the URL location, rather they represent system states and actions that also need to be managed, logged, and reported on.

For example: The Network Timeout category indicates that the Policy Server could not obtain a category due to network latency or congestion. The New URL category is always assigned to the categorization request made when a Network Timeout occurs.

Web-based Categories

Web based categories are the categories that represent content that was successfully downloaded and categorized by the Lenovo NetFilter system.  This includes all categories in the Adult, Information, Entertainment, Miscellaneous, and Security groups.


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