JonDo Help: WWW and privacy

TOC Introduction JonDonym

## The World Wide Web and your privacy

For sure, you can no longer imagine day-to-day life without the World Wide Web. Those numerous services such as online banking, travel information, encyclopedias or the like mean a great convenience in solving your common tasks. Furthermore, you probably surf entertainment and shopping portals, stay in touch with friends over social networks or share your common interests with others in forums. To access the Web you are offered a dozen of stable, highly functional yet easy to use applications, the browsers. The most popular browsers are the Internet Explorer, Firefox, Opera, Safari and Chrome.

Any communication on the Internet leaves all kinds of digital traces which can be automatically acquired, saved and analyzed. Some companies have thus specialized in creating individual user profiles from surfing related data. These databases are of high economic value since they allow an enterprise to comprehensively profile their costumers, that means you. This process is called data accumulation in data mining lingo.

There are many reasons why one should avoid leaving digital traces when surfing: part of the data collected advects into scoring systems which are used to evaluate loan requests, to create individually priced offers or to decide on eligibility for C.O.D. service. Employers may be generated a character profile of their job applicants from traces on the Net prior to hiring them. Freedom of opinion is limited by governments or institutions where they trace individual surfers that use or edit certain web services or deny them any usage at all. Companies may recognize employees of other businesses or even those of their competition and subsequently annoy them with promotional calls or email spam. Browser related data exposes vulnerabilities in the surfing machine. An hacker may subsequently contact the computer directly and attack it.

Further problematic is that these traces are collected, saved, sent and processed without your consent and most widely unnoticed. The actual techniques employed by the data miners on the Web are briefly introduced below.

### Active Web Contents und Scripts

Webcontent accessible by browser plugins such as Flash, Java, ActiveX and Silverlight renders the Web more dynamic and colorful but also more dangerous, for they allow websites to execute code on your PC. If executed, these plugin contents are able to read some details about your computer and network configuration and send it to the web server. By certain manipulations they moreover can read and edit files on your machine and in an extreme case even gain complete control over it. Especially beware signed Java applets: by accepting its signature, the applet, and thereby the visited webserver, automatically receives all user rights on your machine. In particular, it may then read your IP address, your MAC address and even hard disk contents. It does not help to only surf websites you deem trustworthy either. This concept is outdated since nowadays even numerous large and notorious websites are being hacked and filled with malicious code. Only blocking/deactivating these plugin contents provides real security.

The browser scripting language JavaScript ("scripts", "active scripting") is better protected against attacks on your privacy than the aforementioned plugins but not completely safe. Therefore we recommend you to only activate JavaScript contents if needed and to block them otherwise. JavaScript is not to be confused with Java or the active Java plugin, repsective, which is a completely different thing despite the similar name (see above).

You should not surf the Internet without a well secured browser, as your PC is otherwise in danger of being attacked quite soon. Instead of configuring the browser yourself, which takes quite some experience, you may use for example JonDoFox for free. This Mozilla Firefox based browser does not only block all active content at default (you can turn this back on if needed) it is also equipped with further ample security mechanisms. Most websites will still be reachable. YouTube videos and videos of other such portals which are rendered by Flash may be downloaded with special software and then viewed safely with a video player. Websites which demand usage of active plugins should be avoided if possible.

### Cookies

Without cookies, certain services would be complicated to realize in a webserver. If a user requests a page from a webserver, it can not readily match requests of previous pages requested from this server to that same user. Nevertheless, some services require a sort of memory. Shopping portals are an example: a server has to remember what goods were placed into the virtual shopping cart. This "memory" is usually written into cookies, i.e. small text files which are being sent to you by the server upon every page request. When your browser contacts the server again, it also automatically sends back the cookie stored earlier. The server thereby allocates the right shopping cart to you.

But cookies can also be abused to track your steps on the Internet. This works exceptionally well with web portals (e.g. Yahoo) and search engines (e.g. Google) for you use these a lot in order to reach other websites. With cookies, a web host can record large parts of your surfing behavior over years and easily relate it to you as a person with your "accumulated" profile data. Most internet users have collected hundreds of cookies from various websites on their PC without their knowledge. You should thus, in any case and at the latest, delete cookies after your browser session. Modern browsers usually integrate an optional function for this, but it has to be activated by the user first. In JonDoFox it has been made default.

### Browser (HTTP) Header

With every request for a webpage, browsers send information within the framework of the HTTP protocol that can be analyzed by the visited site: language, browser name and version, operating system and version, supported charsets, files, codecs and the last visited webpage. Sending these headers is usually not necessary for rendering websites, but it can be exploited for reidentifying, profiling and analyzing websurfers.

As of today, different filter applications and services have been developed that allow hiding or changing problematic browser headers (e.g. Privoxy, Proxomitron). Unfortunately, these applications can not filter encrypted connections: once you load a presumably "secure" website (HTTPS, browser lock) all filtering fails. Plus, these programs allow every user to define the header data himself. But setting an individual browser type e.g. is in itself what renders you quasi perfectly trackable. Therefore, in JonDo, an automatic filtering has been integrated which allocates an uniform header profile at least for unencrypted connections (HTTP). Those who want to achieve an even higher level of security should rely on JonDoFox though. It always sends the same profile for encrypted connections too. This guarantees that websites may at maximum realize that it is a JonDo user visiting, but not who.

### Browser History

By certain trickery, websites can tell which other websites are saved in your browser history. For this, the visited website embeds special formatting commands (CSS, Stylesheets) that contain external links "of interest" on the pages you visit. If you have visited one of the external websites, your browser will react by executing a command defined in the format, e.g. download a small picture form the website. The website can thereby completely or largely guess the contents of your browser history.

At the moment, there is no reliable protection against this technique apart from deactivating the browser history, which has been made default in JonDoFox.

### Browser Cache

From the contents of your browser cache one can conclude on previously visited, thus already cached, websites: the time required for loading a website changes when part of it is already in the browser cache. By subtle placement of the images on the website, which are loaded one by one, the server can analyze the cache one by one.

Unlike deactivating your browser history, deactivating your cache would have tremendous effect on your surfing speed, which is why we don't recommend it. In JonDoFox a protective mechanism has been integrated instead which bypasses cache for third party content. Also, the cache is deleted automatically when you close the browser. A website can thus no longer gain information about other websites, only about itself.

### Webbugs and Banner Ads

Very likely, you will find one or more cookies in your browser from data miners such as ivwbox.de (INFONLINE), doubleclick.net, advertisement.com or Google, although you have never even visited their websites. This is due to the fact that these enterprises use, on other web sites, a simple trick to nevertheless plant cookies on you and watch your browsing: Webbugs.

"Webbugs" are usually pictures of 1x1 pixels and therefore invisible to the viewer. However, they can also be coded into banner ads embedded in a website. The website contains a picture (webbug) that is loaded from another server running a statistics service (such as Doubleclick, Google Analytics). Thereby the statistics service may set or edit a cookie in your browser unnoticeably. The browser will then send this cookie back to the statistics service with every new request for a site where any webbug of this service is embedded. If the service is used on many different websites, it can now track large parts of your browsing session. If the owner of the statistics service moreover collaborates with the owner of your preferred search engine, he gets an almost complete picture of your internet activities.

The privacy functions of most current browsers that either flatly deny cookies or only deny third party cookies, and alternatively also delete all cookie data when closing the browser, do not achieve optimal protection. To prevent session tracking, all cookies should be blocked by default if possible and only allowed in if needed for the duration of the session. JonDoFox is therefore preconfigured to deny all cookies but allow single websites at the expense of two mouse clicks. We recommend allowing cookies only on a temporary basis, so that they will be automatically blocked again after the session.

Another nasty feature of webbugs is, that they send, besides cookies, also your IP address to the statistics service upon request. Even with a very good browser configuration, by switching off cookies and by using webbug filters, you are never able to reliably prevent this. The only effective protection against this are anonymisation services like JonDonym.

### TCP Timestamps

The Transmission Control Protocol (TCP) is a protocol for transferring data between computers. It is necessary for using internet services like http (WWW), smtp (E-Mail) and ftp. When your computer sends a request for a web site, for example, this data is sent within many small so-called TCP packets. Besides that request data, such a TCP packet also contains some optional information fields (optional headers). One of those options is the TCP timestamp. The value of this timestamp is proportional to the current time of your computer and is incremented according to your computer's internal clock.

The timestamp may be used by the client and/or server machine for performance optimization. However, an internet server may recognize and track your computer by observing those timestamps: By measuring the clock skew of the timestamps, it may calculate an individual clock skew profile for your computer. Moreover, it may estimate the time when your machine was last booted. These tricks work even if you have otherwise perfectly anonymised your internet connections.

If you like, you may switch off those timestamps yourself. The problem is that this might not work on Windows systems. If you use JonDonym instead, you are however protected against being observed this way: The JonDonym mixes automatically replace your potentially insecure TCP packets by their own.

### MAC Address

The MAC address (MAC=Media-Access-Control, sometimes also called Ethernet-ID, Airport-ID or physical address) is the hardware address of each individual network device. Each computer may have several of such physical or virtual network devices (bound to a cable (LAN), wireless (WLAN), mobile (GPRS, UMTS), virtual (VPS), ...). The MAC address serves as a unique identifier for the respective device in a local area network. On the internet, it is neither used nor transmitted. Also, your access provider may only see it if your computer is not connected to the internet over a router, but directly, for example by a modem. You may moreover change the MAC address yourself.

### IP Address

The IP address is given to you by your provider on dialing into the Internet. The provider usually saves it for months or even years together with your customer data and your online time. It is your distinct identifier on the Internet which is sent along whenever you make a direct connection to any internet service. The IP address tells the server where to send his response. As long as your IP does not change, it is easy to monitor when and what website you have contacted. The IP also reveals your provider, many times your location and sometimes (in case of a company or computer center) even what terminal you are on. In many cases, an IP address relates directly to one person.

Some of the information that is given away by your IP or browser can be reviewed on the JonDos test page.

While the traces mentioned so far can be blurred without any special services needed, the same can not be said about your IP address. That is why the software JonDo has been developed: In order to blur any connection between your IP and the websites you visit, JonDo connects to the service JonDonym. This service then interlaces the servers of different organizations with your PC and the Internet. You are now surfing with the IP of the respectively last server within a chain/cascade of a few so-called mix servers. The data sent by you is separately encrypted for every mix server and slightly altered in size and sequence so that nobody can eavesdrop on or guess your data stream. You are therewith protected even for the case that some (but not all) operators get hacked, bribed, threatened or otherwise forced to observe your access.

TOC Introduction JonDonym