URL filter FAQ

Here you can find the answers to many frequently asked questions about ufdbGuard, the URL filter for Squid.  Feel free to contact the support desk if you have a question that is not answered here.

What is a URL database?
What are the requirements to use ufdbGuard?
Is ufdbGuard really free software?
Is Linux supported?
Is LDAP supported?
Is ICAP supported?
How does URLfilterDB work?
What is ufdbGuard?
What is Squid?
Can I use the URL database without ufdbGuard?
Can I use ufdbGuard without the database of URLfilterDB?
What web proxies can use ufdbGuard?
Can ufdbGuard replace squidGuard?
What web content can be blocked?
When is a site included in a blocked category?
What adult content can be blocked by URLfilterDB?
Does ufdbGuard block UltraSurf ?
Does ufdbGuard block Tor ?
Can I overrule categories?
Can I suggest a URL be added to or removed from the database ?
What is the difference between a URL filter and a content filter?
Why is the HTTPS protocol a security risk?
How can I configure ufdbGuard?
Does ufdbGuard consume much memory?
What is the ufdbGuard API?
What is "end of life" ?
I want to install ufdbGuard, but compiling the ufdbGuard code results in errors
How can I test URLfilterDB before buying?
How much does a subscription to URLfilterDB cost?
How can I make payments for a URLfilterDB subscription?

 

What is a URL database?
A URL database is used by URL filtering software to selectively block access to unwanted web content.
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What are the requirements to use ufdbGuard?
You need the following hardware and software to use ufdbGuard:
Hardware: The hardware requirements depend on the number of users.
Memory: 256 MB on 32-bit systems
512 MB on 64-bit systems
Free disk space: 2 GB
CPU any CPU that runs Linux, FreeBSD or Solaris
CPU number and class:
< 100 users: 1 CPU, class: Pentium 3
100 – 750 users: 1 CPU, class: Pentium 4, 2.8 GHz or better
750 – 2000 users: 2 CPUs, class: Pentium 4
> 2000 users: 2 CPUs, class: Intel Core 2 Duo
Software:
Operating system: Linux, FreeBSD, or Solaris
Web server software: Apache
Web proxy: Squid
Internet filter software: ufdbGuard
Both the popular Squid web proxy and our ufdbGuard internet filter software are free!
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Is ufdbGuard really free software?
Yes.  ufdbGuard has always been free software with a GNU GPL2 license since its first release in 2005.
Also note that ufdbGuard can be used with any text-based URL database and/or with our commercial URL database.
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Is Linux supported?
Yes. ufdbGuard is developed on Linux 2.6.32 (CentOS 6.x) and tested on on various platforms.
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Is LDAP supported?
Starting with version 1.30 LDAP support is easy to integrate due to the new configuration feature execuserlist which also supports Active Directory, Kerberos and any other queriable database with usernames.
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Is ICAP supported?
Release 2.0 will support the ICAP protocol, and hence all web proxies that use the ICAP protocol to filter URLs.  Contact the support desk if you are interested to become a beta tester.
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How does URLfilterDB work?
In most companies, web browsers like Internet Explorer use a web proxy to visit the Internet. The web proxy can be extended with an Internet filter to block the content of certain web pages. The ufdbGuard Internet filtering software uses the URLfilterDB database to decide which web content is filtered. For more information, we refer to the "How it works" page on this site.
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What is ufdbGuard?
ufdbGuard is the fastest internet filter that can be used with Squid. ufdbGuard is free and can be downloaded freely.
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What is Squid?
Squid is a popular and free web proxy. A web proxy sits in between a web browser like Internet explorer and the Internet. Squid and ufdbGuard integrate seamlessly.
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Can I use the URL database without ufdbGuard?
No. The URL database comes in a format suitable for ufdbGuard only.
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Can I use ufdbGuard without the database of URLfilterDB?
Yes. ufdbGuard comes with a program to generate a .ufdb file from a plain text file or URL blacklist.
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What web proxies can use ufdbGuard?
At this moment, Squid is the only proxy server that ufdbGuard supports.
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Can ufdbGuard replace squidGuard?
Absolutely! ufdbGuard is an excellent alternative for squidGuard because it is backed by a support desk, has regularly new features and bug fixes, and is 3 times faster.
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What web content can be blocked?
The URL database contains a set of website categories (also known as “blacklists”). The administrator can choose which URL categories are blocked for access, and which URL categories the users are allowed to visit.
URLfilterDB has the following categories :
  • Adult & sexually explicit, including obscene content
  • Advertisements
  • Audio & video
  • Chat
    subcategories: AIM, Ebuddy, Facebook, Google, ICQ, MSN, Oovoo, Skype, Whatsapp, Talkatone, Yahoo messenger
  • Dailymotion
  • Dating & Personals
  • Drugs
  • Entertainment
  • External Applications
    subcategories: Citrix Online, iCloud, Telegram
  • Finance & Investment
  • Forums
  • Gambling
  • Games
  • Hacking & Warez
  • Job Search & Career Development
  • Malware
  • Microsoft Data Collection
  • News
  • Peer-to-peer (P2P)
  • Personal weblogs & private home pages
  • Religion
  • Search Engine
  • Shops
  • Social Networks
    subcategories: Badoo, Facebook, Google+, Twitter
  • Sports
  • Browser toolbars
  • Safe sites
    subcategories: Google Safebrowsing, Microsoft Smartscreen
  • Travel
  • Violence/Offensive & Hate
  • Vimeo
  • Web Proxies, anonymizers and all filter circumvention sites
    subcategories: Teamviewer, Silk (Amazon), UCweb, Puffin Browser, Translators
  • Web Radio
  • Web TV, includes all sites with lots of videos, including Youtube
  • Web-based email
  • Youtube
  • Browser-specific: Mozilla, Chrome
The administrator can add any number of user-defined categories to whitelist and blacklist (parts of) sites.
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When is a site included in a blocked category?
A site is included when it contains one or more items that fit into a category. To prevent blocking too much, the database is built with a policy to include only subdomains of sites whenever possible. For example, if site1.com has a separate adult section in adult.site1.com, only this subdomain is included in the adult category. This means that www.site1.com is not in the adult category. On the other hand, if www.site2.com has a mix of adult and non-adult material that is not clearly divided into subdomains or subdirectories inside a domain, the whole domain is included in the adult category.
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What adult content can be blocked by URLfilterDB?
The adult category includes sites that contain hardcore and softcore porn, nudity, erotic stories, erotic art, fetishes, escorts, adult portals, lingerie and sites where one must be over 18 to enter. Any "non-adult" site that has an explicit adult advertisement is also included in the adult category!
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Does ufdbGuard block UltraSurf ?
Yes, UltraSurf is blocked when the options to verify SSL certificates for HTTPS connections and block HTTPS for URLs which have no fully qualified domain name (FQDN) are used.
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Does ufdbGuard block Tor ?
Yes, Tor is blocked when the options to verify SSL certificates for HTTPS connections and block HTTPS for URLs which have no fully qualified domain name (FQDN) are used.
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Can I overrule categories?
You can block a category as a whole, while still allowing access to one particular website in that category. Just include this website in the exception category "always allow"; this prevents blocking.
If you want to block access to a single website that is not in any category (e.g. www.fbi.gov), include this site in the category "always deny".
Both categories are maintained by the proxy administrator, and never by URLfilterDB!
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Can I suggest a URL be added to or removed from the database?
You can suggest any URL for inclusion or removal of the blacklist using our website.
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What is the difference between a URL filter and a content filter?
A URL filter uses a URL database with verified domains to block domains. A content filter guesses the nature of each page of each website "on the fly", by scanning the web pages for words like "sex".
A URL filter has several advantages over a content filter. For instance, a URL filter can block HTTPS traffic, while a content filter cannot because HTTPS is encrypted. Moreover, the risk of an incorrect classification is significantly higher with content filters. Also, CPU requirements for content filters are generally higher than for URL filtering solutions.
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Why is the HTTPS protocol a security risk?
HTTPS encrypts all data that is sent between a client and a web server.   This is useful for prohibiting eavesdropping on the data while it is transported over the Internet.  But it also enables setting up so-called “proxy tunnels” between a PC on a protected network and any system on the Internet.  Using a proxy tunnel, any system on the Internet can set up an unauthorized connection to a system on the protected network.  ufdbGuard offers the unique feature of dynamically detecting and blocking proxy tunnels.  A more detailed explanation is given in Why HTTPS is a security threat.
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How can I configure ufdbGuard?
ufdbGuard is extremely easy to configure. Once you have defined the blocking policy (e.g. which categories of sites to block), just enter this policy in the ufdbGuard configuration and you are ready to use it!
ufdbGuard is powerful and has many features and the support desk responds to all questions about the configuration within 1 business day.
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Does ufdbGuard consume much memory?"
The memory requirements are modest: 200 MB on 32-bit systems and 350 MB on 64-bit systems.  The virtual memory usage on modern 64bit Linux systems, however, is very large and is caused by the system memory allocator, malloc (see also "man malloc").  Malloc uses large virtual segments although it allocates relatively small parts inside these segments and therefore the process gets a very large virtual memory size.  In version 1.32 the configuration file /etc/sysconfig/ufdbguard contains the environment variable MALLOC_ARENA_MAX which has the value 12, to reduce the size of the virtual memory that ufdbguardd uses.  If necessary, this variable can be set by the administrator for older versions of ufdbguard.

 

What is the ufdbGuard API?
The ufdbGuard API is a library that can be used by 3rd party applications.  The ufdbGuard API provides a simple interface to the URL classification engine and hence gives system integrators and solution vendors access to a powerful API which performs extremely well.  Contact us to receive more information.

 

What is "end of life" ?
ufdbGuard is released two or three times per year. The support desk usually only supports the three most recent versions of ufdbGuard and may declare older versions of ufdbGuard "end of life".  The support desk of URLfilterDB does not support versions declared "end of life".

 

I want to install ufdbGuard, but compiling the ufdbGuard code results in errors
If you get errors during the compilation of the ufdbGuard sources, the most likely cause is that the OpenSSL or Bzlib header files cannot be found. In this case, install the packages libssl-devel and libbz2-devel from the Linux installation media.
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How can I test URLfilterDB before buying?
On this website you can register for a 60-day trial version of URLfilterDB to test it against URL filters and content filters. We are confident that you will find that URLfilterDB’s speed and accuracy of blocking much superior to its competitors.
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How much does a subscription to URLfilterDB cost?
Use the quote request form to ask for a subscription quote for your organization. Alternatively, use the ROI calculator to see how little time your ROI on URLfilterDB will be!
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How can I make payments for a URLfilterDB subscription?
We accept payments by international money transfer to our bank account in the Netherlands. The invoice contains all details to make a transfer. Customers in Euro countries will always be billed in Euro. Other customers may choose to be billed in EUR or USD.
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