ICSI Netalyzr

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Frequently Asked Questions

I have a question about my results. How can I get in touch?
We run a mailing list at http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/netalyzr. To contact us privately, please send email to netalyzr-help@icsi.berkeley.edu. If you have a question about a particular session, please include the session ID. It is shown in the status bar during the analysis, and stated explicitly as the session's permalink at the top of the summary page. You can also just cut-and-paste the URL shown by your browser for the summary page.

What information do you collect?
We collect effectively the same information we present to you in the summary page, and nothing else. All of this information is collected from network connections the applet initiates itself.

There is no launch link on the start page. Why?
Your system needs to provide a Java Runtime Environment (JRE) for applets to operate in. Please ensure that a JRE is installed on your machine, and that Java is enabled in your browser. You can test your installation by visiting Sun's Java detector.

Why Java?
We are unable to perform all of the tests we provide using more lightweight alternatives, such as JavaScript. In particular, JavaScript does not enable the browser to create arbitrary network connections.

How do I install Java?
First make sure your browser is willing to use Java and then reload the front page:
In Internet Explorer 7, go to Tools Internet Options Programs Manage add-ons and ensure that the Java plugins are enabled.
In Firefox, make sure the "Enable Java" tick box under Preferences Content is selected.
In Safari, make sure the "Enable Java" tick box under Preferences Security is selected.
If that still doesn't work, follow the instructions at at http://www.java.com/getjava/ to download and install Java.

Why JavaScript?
Some information, such as cookies or framing, can't be detected within Java but can be detected by JavaScript. Thus in addition to the Java applet, there is a small amount of JavaScript on our analysis page to perform these checks.

Are you accessing any information on my computer?
We do not touch any files on your disk. The only system-local information we use is your local time, what IP address Java believes has been assigned to your machine, and what information your browser routinely exposes (its "user agent" and cookies it automatically provides because you have visited our sites before). All other information is obtained from the network.

Are you probing my local network?
Almost all network connectivity is exclusively with your DNS resolver, our servers, and any proxies in front of them. There are only two exceptions. The first is that, if the user is behind a NAT, Netalyzr attempts to check if the NAT is operating a DNS proxy or resolver and, if so, checks that this proxy is operating correctly. The second is a test for Universal Plug and Play (UPnP) support, a protocol used to talk to NATs, media players, and other devices in the home. Netalyzr uses UPnP to ask "Are there any NATs?" and, if any NAT replies, "What sort of NAT are you?".

The results state the applet was not permitted to conduct all tests. How can I allow the tests?
The applet operates within the confines of the security policy enforced by your Java runtime. When the applet attempts to perform an operation that violates this policy, a security exception is thrown, and the operation is not executed. Browsers handle these security restrictions in a variety of ways. By confirming that you trust the applet, many browsers will allow the applet to conduct all tests. However, some Java installations will not allow certain tests to run, even if the user gives consent. If you are asked to confirm individual operations, we suggest to permit them as required to complete the tests.

My anti-virus program triggered an alert while Netalyzr was running. Why?
As part of our content-filtering tests, we download the EICAR antivirus test file into the applet. This file is harmless and designed to test correct functionality of antivirus software. Any related warnings or alerts thus merely signal correct functioning of your antivirus installation and can safely be ignored.

Netalyzr reports large buffers in my up/downlink. How can I fix that?
The first option is just to be aware of the issue. If you don't try to perform large file transfers or P2P applications while also websurfing, gaming, or using VoIP, you shouldn't notice a problem. Buffer sizing is only a problem if you try to perform both large transfers and interactive applications simultaneously.
The second is to pay for a higher bandwidth service, if it is important for you to be able to perform both large file transfers and interactive applications at the same time. The problem is due to the ratio between the buffer's capacity and the bandwidth of the connection, so if you pay for more bandwidth, the buffering problem is reduced.
Unfortunately the real solution, namely access devices which allow programmable buffer sizing or dynamically resize their buffer based on available bandwidth, is not generally available to the customer at this time.

Who developed Netalyzr?
Netalyzr is developed by the Networking Group at the International Computer Science Institute, an independent non-profit research institute affiliated with the University of California, Berkeley, USA.

What's the connection between the name Netalyzr and Safer Networking?
Our Netalyzr is unrelated to any of Safer Networking's products. However, Safer Networking holds a trademark on the name NetAlyzer. We chose the name for our tool before we had learned of this conflict. Safer Networking has graciously agreed to allow us to continue using the name.

Who funded this work?
This work is sponsored by the National Science Foundation, the Department of Homeland Security Science and Technology Directorate's Cyber Security Division, and by generous gifts from Amazon, Comcast, and Google. Heise Netze for funding the translation services for the site's German version.