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    • FileZilla Open Source FTP Client and Server By Devin Funk Quan “Vincent” Cu Kenny Pullin Abstract: FTP client applications are designed to upload and download files over any type of network while providing a simple user application interface. Weather your using the WWW or a small business network, FileZilla accomplishes this goal using a long established internet transfer protocol that is fast, robust, lightweight, secure, and most of all easy to learn and use. FileZilla was developed with all the functionality you would find in commercial applications and supports most operating systems used today by businesses and home users throughout the computer industry and the world. Above all FileZilla is Open Source which makes it free for anyone to download and use with the simple click of a mouse.
    • Contents Abstract:.......................................................................................................................................................1 FileZilla: A Brief History................................................................................................................................2 FileZilla Client Application............................................................................................................................2 FileZilla Server Application...........................................................................................................................3 Summary....................................................................................................................................................13 FileZilla: A Brief History FileZilla was started in February 2001 by Tim Kosse, along with two associates in a computer science class, and has grown to what it is today, a full scale file transfer protocol (FTP) client and server with features that surpass FTP commercial applications, and best of all it is free to anyone who wants to download it. FileZilla Client Application The FileZilla FTP Client is a full service open source file transfer protocol (FTP) client application that has all of the features of the most reliable FTP software applications on the market today. Besides the resources included with FileZilla the client application has its own server that can be used to ‘publish’ and test web pages or files on your own operating system and personal computer before downloading them to a remote site, to save time while developing. Some of the features FileZilla includes are support for most of the popular operating systems used today. The operating systems supported by FileZilla include the older versions of Microsoft Windows 32-bit processors used for Windows 95 and 98 along with all the newer versions of Windows including the 32-bit versions of NT, Windows 2000 and XP. Some of the advanced functions on FileZilla are provided by the Site Manager, these include drag and drop file transfer, for easy publishing or simple file transfer using the mouse. FileZilla supports import and export of web sites and settings from one application to the other. To use this function you can access your files from the Edit command button on the FileZilla browser interface and select import or export. When using FileZilla FTP Client and Server Page 2 5/4/2010
    • this on the system hard drive or to the system registry. You can function append ftp server addresses to the command line in FileZilla. there are DOS provides command line support in the form of switches two using FTP as the access protocol and can be used to access options, folders on the server from a remote location or the system file one is to server of the computer you’re working on. This can be save convenient if there is no other access provided by the them to application on a machine you’re developing files on. As an the example suppose you were working on another machine using filezilla. say Macromedia as your development suite and you wanted to htm file publish your files on a machine that didn’t have FileZilla located installed. Using DOS as the FTP client you could upload your files to your FileZilla Client and access them later when you were back on the machine you normally develop on. FileZilla Server Application FileZilla Server has several features that are comparable to or better than many closed source ftp applications. One of them is the support for secure file transfer protocols (SFTP) on the server which the user can implemented to insure no files are compromised during uploading or downloading of personal information or private applications. Like FileZilla the server also support several advanced functions like security protection from behind a firewall or by using a router. FileZilla has the ability to work behind a firewall or a router using either dynamic or static web addresses. This is done by configuring the ports on your firewall to allow incoming connections on the ftp port (default: 21), as well as allowing outgoing connections from the server. The server supports file aliases on both the home directory and any other directory by renaming the files. “Let's assume you have two shared folders: c:ftproot is your homedir and d:myfiles is the second one. In order to display an alias to d:myfiles in your homedir, add c:ftprootmyalias as alias to d:myfiles. A new folder with the name myalias will appear in your homedir with the contents of d:myfiles.” (Project..2005) FileZilla Technical Background FileZilla FTP Client and Server Page 3 5/4/2010
    • FileZilla is an S/FTP client that allows users to connect to Secure File Transfer Protocol, SSH File Transfer Protocol, and File Transfer Protocol Servers. The term S/FTP is used in this white paper to denote all three of these protocols. Standalone FTP is the oldest of these three technologies. FTP is a protocol designed for file transfers between a server and a client. It operates on port 21 in the TCP/IP scheme, which is dedicated for FTP use. FTP is not inherently secure by itself. When a client logs into an FTP server there are two setups they may encounter. The first methodology is open access to anyone. A user specifies a username of “anonymous” and for password traditionally enters their e- mail address. However, normally all modern clients input a generic address for password when an anonymous option is selected. The second methodology in setting up an FTP server is to require users to authenticate with a given username and password. This login-password combination may either be given to an individual or group. For example an FTP server containing academic data may have a login- password for all research assistants to access the appropriate folders but also have a login for senior research faculty to have access to those folders and more. FTP works beautifully for many tasks but has one primary security flaw. When a user authenticates, their login and password is transmitted unencrypted from the client to the server. This means anyone could intercept the data with something as simple as a packet snifter and retrieve the login and password. This basic flaw of FTP was one of the reasons for the creation of SSH FTP and Secure FTP. Secure FTP is the same basic protocol as FTP and runs on port 21 as well. Secure FTP is identical except for the fact that it employs SSL/TLS encryption. A server wishing to use SSL/TLS encryption will need to either purchase a public certificate that is signed by major issuers such as Thawte or Verisign or create their own private certificate. It is via these certificates that encryption is established between the server and the client. Once an encryption certificate has been accepted by the client an encrypted connection can be assumed to exist. When a client such as FileZilla tries to connect to a Secure FTP server it must FileZilla FTP Client and Server Page 4 5/4/2010
    • already know which encryption standard is in use. Once it tries to connect with the appropriate encryption protocol, the client will be prompted to accept the certificate. If it is a publicly signed certificate of a reputable name than a user will automatically know if it is authentic. If a user encounters a private key it is prudent that it be examined to be reputable. Private keys can be created by anyone so for truly secure purposes they should be rejected. Any organization that is serious in its security commitment will have a public certificate for encryption. This use of encryption and certificates is identical to encryption use on the web. For example, when a user purchases and item form an online merchant the connection is encrypted. The padlock that appears in browsers indicates this. This presentation and acceptance of certificates is transparent to the user. This is because these certificates are publicly signed by third parties that are recognized automatically as authentic by the browser. The next technology is the most recent and is based on completely different technologies than FTP. SSH FTP actually runs on top of another secure protocol known as SSH. SSH stands for Secure Shell and is a technology used to connect to Unix and Linux systems securely. SSH is used for a variety of things that are beyond the scope of this white paper. What is important to know is SSH creates a secure encrypted tunnel between the client and the server. This encryption is done through the same certificate process as described for Secure FTP. SSH FTP runs on a different port than FTP and Secure FTP, port 21. This is because of these fundamental differences in how SSH FTP functions compared to FTP and Secure FTP, With all of these types of FTP protocols, once the connection has been established, their behavior is very similar. When a FTP server is set up a root for the files available to FTP users is set. This root limits which files on the computer running the FTP server can be visible to users. An FTP server will have a default directory for a user to be taken to initially. This may be the same for all users on the server or different for different users. Different permissions FileZilla FTP Client and Server Page 5 5/4/2010
    • for different folders can also be established. For example some folders may be read-only while others may be full access. All of these properties are completely configurable with an FTP Server like FileZilla. FileZilla currently support FTP and Secure FTP only. FileZilla Server does not currently support SSH FTP Comparison Open Source and Close Source Clients There are many FTP shareware available on the internet with no cost, like FileZilla, CoffeeCup Free FTP, AceFTP, Core FTP LE etc. However, a numbers of FTP software charge over two hundreds to two thousands USD for one year subscription, like WS FTP, WS FTP professional 2006, FTP Voyager, Serv-U, Zeap etc. This will create a question for anyone, who going to buy these FTPs software when many free sharewares are available? Then, it must be some different benefit between those free shareware and the costing service. For comparison purpose, FileZilla and WS FTP professional 2006 will be use in the compare below. The shareware like FifeZilla was created by a small group of people. The developers of FifeZilla created this for a class’s project. Then, they released it on the internet at an open source for two reasons. First of all, this was created for personal use and to gain personal experience. Second, the developer “didn’t think that they would sell even one copy if we made FileZilla commercial” (FileZilla, 2005), because this was not fully developed. Lastly, they want to gain more “experience and idea from other people thought open source” (FileZilla, 2005). This is also the case for other sharewares, the developer has knowledge about computer programming. They create the software for their own needs, and make it available on the internet with no cost. For this reason, there are many open source FTP programs on the internet. Contrast with the open source, the close source FTP was created by a company with a group of professional programmers. WS FTP pro was created by Ipswitch Inc. FileZilla FTP Client and Server Page 6 5/4/2010
    • The main reason for the Ipswitch to create WS FTP is provide the service to small, midsize organizations and individual who want a high quality program and professional support. For that service, Ipswitch will gain the financial profit. For individual user, Ipswitch sells the WS FTP professional 2006 2 pack with Service Agreement for $119. With the multi-user packs and site licenses for 50 users that cost over two thousands (Ipswitch, 2005). With this high cost, what are the requirements the buyer expecting? The mainly requirement of the users are the level of secure and reliable of the service. For example, Toyota Racing Development (TRD) is a department of Toyota Corporation. Their task is developing racing part for Toyota racing team and upgrade parts for many Toyota vehicles. TRD has two facilities, one locate in Tokyo, Japan and the second one at Los Angeles, California. At 5 p.m. everyday, engineers in Los Angeles facility transfer all of their files to Tokyo, and at the end of the work day in Tokyo, the information once again being transfer back to Los Angeles. This is helping their engineers communicate between two facilities, and keep the project going 24 hour a day (Toyota, 2005). In order for TRD can keep their projects develop quickly and effeteness to compete with other car manufacture. However, these data are very important that can be worth million dollars, TRD need a very secure way to transfer these data. That will require the secure level of WS FTP professional 2006, it “offer 256-bit Advanced Encryption Standard (AES) keys with SSL transfers, making data encrypted with AES secure enough for classified government use.” (Ipswitch, 2005) Then, the cost for Ipswitch service is small compare to the cost of TRD’s data. This also a reason for many organizations is paying for the service of those close sources FTP. In addition, the close source FTP been developed by professional with error free, high lever customization and more features. These features are including multi-part download, synchronize utility, Auto reconnect, auto retry etc. With the service agreement the user can have access to the serve of the provider, the transfer speed can up to 600 FileZilla FTP Client and Server Page 7 5/4/2010
    • kB/s for download and 120 kB/s for upload. For FileZilla, the maximum transfer speed is up to 10 kB/s (FileZilla, 2005). The close sources have numbers of benefit over the open sources. However, for home users and students, they don’t need high level of secure and reliable to transfer pictures, mp3 files, and homework files. Then, the feature of the open source like FileZilla with not cost is enough for them. Open source is provide with no cost, the close sources have numbers of feature and high secure level, then the final decision is depend on the requirement of the user. Practical use of FTP There are many methods to transfer file on the internet. For example is e-mail attachment, instant messenger or FTP. FTP is File Transfer Protocol that is a popular -method to exchange file over the internet. For most user e-mail attachment is an easy way to transfer file from one user to another or from one computer to another. However, it is limit the file’s size. A typical e-mail can be transfer an amount of data less than few megabytes. One seven mega- pixel picture can be 3 to 4 megabytes of data. With a file have a size bigger than 10 megabyte cannot transfer file using e-mail. In addition, it requires accesses to the computer that contain the file and the computer that receive the file. This will also take a long amount of time to upload and download the file. Today, people are transfer pictures, music files like MP3, movie, game and program all over the internet. These files are very big. Their size is from 3 megabyte to 700 or 800 megabyte. Even with the receiver has a broadband connection, but the file can be transfer with a speed that lowers than one hundred megabyte per second. With the 700-megabyte file, the process can take few hours with the connection has not been interrupted. If the connection has been lost, the user has to start to download from the beginning. There are number of program to help user transfer file on the internet with high speed and avoid the interrupt connection like Napster, Kazaa, Flashget, E-Mule, I-Mesh etc. This is usually call peer-to-peer transferring. FileZilla FTP Client and Server Page 8 5/4/2010
    • The backbone of these programs is using File Transfer protocol (FTP search, 2005). The FTP method can transfer the file with the size up to a gigabyte, and each computer use FTP have the FTP address then the receiver can reconnect to the source. File Transfer Protocol can be access from one computer and can be perform by one user either the receiver or the user from the source. Download a file from the internet is actually transfer file from another computer. The download user can select transfer the file with only the action from him or herself. Another using for FTP is transfers a file from a personal computer to the school or work directory or back. I can access a file in my Purdue career account that locates in the H drive of the Purdue server using FTP secureFX. FTP is so convenient, because that I do not need to physical go in school using a school’s computer, and this is can be access 24 hours a day and seven days a week as long as Purdue server is running. With benefit of the FTP over other method of files, transfer on the internet like the large amount of file can transfer. The reliable of the transmission control protocol (TCP), and the requiring of only one user to perform the task that make FTP is a useful tool for the webmaster or people who creates a personal web page. In addition, many of the company are using FTP to transfer data between their facilities make the business in best communication. Today, many people are using FTP whether knowing it or not (FTP search, 2005). Alternative Transfer Methods of S/FTP There are several alternatives to the client/server architecture S/FTP provides. One of the newer alternatives to file distribution is Bittorrent, a program developed by Bram Cohen. Bittorrent works in a completely different way then S/FTP. Rather than a client/server architecture where clients log into a server and then there is a one way transfer, Bittorrent is a decentralized system. Someone wishing to distribute a file with Bittorrent will first create a tracker. A tracker is a program that maintains a torrent. The actual data FileZilla FTP Client and Server Page 9 5/4/2010
    • of the file would not be in this tracker, rather its sole purpose is to maintain a list of those who are currently downloading and uploading the data. A user wishing to download a file would download the .torrent file which contains the internet address of the tracker and the hashes for the file. Hashing is part of the built in security of Bittorrent. Whenever a user downloads a piece of the torrent a consistency check is run. If the hash result generated does not match that of what the torrent indicates, the piece is rejected and downloaded again from a different source. The remaining question is where does the actual data come from? The answer is simple. While a user downloads pieces of the torrent, they are required to upload the data they have already downloaded. In theory, the faster a user uploads the faster their download will be. It is considered polite to leave a torrent open after it is finished until a download/upload ratio of 1:1 is achieved. Someone wishing to host the file can “seed” the torrent which is the equivalent of leaving a torrent open after a download has been finished. From a commercial distribution standpoint, the distributor of the content can seed the data on a fast connection, but bandwidth costs will be severely mitigated by having other users upload as they download. Another benefit of this method over traditional client/server transfer is that in those traditional scenarios, a server can become overloaded and become slow or crash. With the Bittorrent system, the opposite is true. The more popular a torrent becomes, the stronger it becomes. You cannot swamp a torrent. More down loaders will create more up loaders meaning faster downloads for everyone. There are caveats to this system of distribution. The distributor loses some control of their content. They do not control the sole source completely. Integrity is maintained through hashing as to avoid poisoning of data, but methods to restrict access or authenticate users are limited. A distributor could temporarily halt distribution of the content by taking down the tracker. However, intrepid users could publish a new torrent based off of the old one and continue distribution. It should be noted that this risk is also valid FileZilla FTP Client and Server Page 10 5/4/2010
    • with client/server distribution. A user could leach the content off of the server than host it themselves. Security in terms of restricted access is much more limited in Bittorrent versus S/FTP. With S/FTP multiple accounts can be created that force users to authenticate. Bittorrent tracker can be locked down to only allow certain IP addresses to connect to it. In this situation a distributor would require a user to register their connection before downloading. This works by registering the originating IP address of the registration request. However, anyone who uses the same IP addresses as that user, for example multiple users on a single connection behind NAT, will also have access. For these reasons securing access to a torrent is unwieldy and not sufficiently secure for many applications. There are also other methods for file distribution besides S/FTP and Bittorrent. Web hosting on a web server works for simple purposes. For example, a web page could have a simple link to a file on the web server for users to download by simply clicking the hyperlink. The caveat of this method is lack of control. There is no authentication on the user’s part to prevent access unless there is complex server file system security based access control through ACLs (Access Control Lists). This kind of server configuration can become tedious and cumbersome when hosting a multitude of files. One key feature of SFTP that none of the above offers is the encryption. All communication between the server and client with SFTP is encrypted preventing interception of data. Neither Bittorrent nor web hosting support this natively. These different forms of file distribution are suited well for different purposes. S/FTP works well for files that are only needed by a select few and where security is a primary concern. Bittorrent works well for the heavy distribution of large amounts of data where security and restriction of access is not a concern. Web server hosting works well for small files that require no access restrictions where a simple interface is required. FileZilla FTP Client and Server Page 11 5/4/2010
    • FileZilla FTP Client and Server Page 12 5/4/2010
    • Summary Summarize the benefits of the Praxis solution. FileZilla FTP Client and Server Page 13 5/4/2010