Which of the following protocols transfers files without any authentication or security?

4.4.2 FTP

FTP, the File Transfer Protocol, enables users to transfer files between computers. As Figure 4.11 shows, FTP opens two connections between the computers: one connection for the commands and replies and the other for the data transfers. FTP is interactive. Its commands are send, get, transfer, and cd (change directory). FTP transfers files in three modes: stream, block, and compressed. In the stream mode, FTP handles information as a string of bytes without separating boundaries. In the block mode, FTP decomposes the information into blocks of data. In the compress mode, FTP uses the Lempel-Ziv algorithm to compress data.

II.C.1. File Transfer Protocol (FTP)

FTP is an application layer protocol that is used for transferring both text and binary files over the Internet. The FTP client process uses a randomly assigned TCP port number x, usually above port number 1023, to establish a control channel to request an FTP connection with an FTP server process listening at the well-known TCP port 21. In the normal mode, the server process uses TCP port 20 to set up a data connection with port number y on the client where y > 1023 and x ≠ y. In the passive mode, the FTP server process uses a port above 1023 for data connection to port y on the client.

FTP

The FTP utility provides client access to remote FTP servers to transfer files over FTP. Files can be transmitted or received in either text (ASCII) or binary mode. The syntax of this command is:

Table 12.15 lists the different parameters of the FTP command.

Table 12.15. Parameters of the FTP Command

ArgumentDescription-vSuppresses server responses.-dEnables debugging. Displays all messages sent between the server and client.-iDisables interactive prompting.-nSuppresses the ability to log on automatically when the initial connection is made.-gDisables file globbing. Glob permits the use of wildcards.-s: FileNameFileName specifies a script file containing FTP commands to execute.-aSpecifies that any local interface can be used.-w: WindowSizeSpecifies the size of the transfer buffer. The default size is 4096.-ALogs into the ftp server anonymously.HostThe remote FTP server to which to connect.

When connecting to an FTP server, you will be prompted to authenticate before being granted access. Public FTP sites allow anonymous FTP access. To log on anonymously, you can specify the –A switch or you can log on as shown in the following example:

When this command is executed, the output is displayed as follows:

Once you're logged on, you can perform several functions, such as getting directory listings, navigating the directory tree, and of course, downloading and uploading files. Table 12.16 explains different FTP commands available in Microsoft's implementation in Windows XP and Windows Server 2003. It is important to note that different operating systems support different FTP commands, and the commands discussed in this section may not be available in some other operating systems.

Table 12.16. FTP Commands Available in Windows XP and Windows Server 2003

CommandDescription!Repeats last command.append LocalFile [RemoteFile]Appends the local file to the file on the remote server.AsciiSets the connection to transmit in ASCII format.BellSounds the computer tone when a file transfer is completed.binary | binSets the file transfer format to binary.ByeDisconnects from the server and exits FTP.cd [Path]Changes the directory to the given path. If executed without any parameters, prints the current working directory.CloseCloses the connection but does not exit the FTP client.DebugToggles the debug mode.delete RemoteFileDeletes the remote file.DirPrints a directory listing of the current working directory.DisconnectDisconnects from the remote server.get [FileName]Starts downloading the given file.GlobToggles globbing (the use of wildcards).HashPrints a hash character (#) for every 1,024 bytes.HelpPrints help.LcdChanges the directory on the local computer.literal ArgumentSends a literal (raw) command to the FTP server.LsPerforms a directory listing.mdelete [Files]Deletes multiple files as per the pattern or file list provided.mget [Files]Downloads multiple files as per the pattern or file list provided.mkdir [Directory]Creates a directory.mput [Files]Uploads multiple files as per the pattern or file list provided.put [File]Uploads the given file.QuitDisconnects and exits FTP.

FTP Basics

FTP was defined in RFC 959 and updated in RFC 2228, RFC 2640, RFC 2773, RFC 3659 and several others (be careful of the errata). One major difference between FTP and almost every other application is the fact that FTP employs not one but two ports between client and server. One explanation is that there is always an available control connection to quickly countermand actions that have unintended or unexpected results. But RFC 959 simply notes that the control connection essentially uses the remote access telnet protocol, leading one to believe that the developers wanted to use something already existing.

The FTP control connection is set up in the usual client–server fashion. That is, an FTP server process (such as ftpd) is listening for clients’ connection requests. The number of simultaneous clients an FTP server can accept varies and is usually a configurable parameter, but limits well above 100 are not unusual.

The FTP server requires a log-in from the user, and in some cases servers allow a special log-in for anonymous FTP. The user is supposed to use their email address as a password, a primitive auditing measure. Anonymous FTP implementations used to allow users to simply press Enter and leave the anonymous password field blank, but many FTP implementations now demand at least something at the password prompt. Some do not allow more creative substitutes for an email address, and many FTP servers check for things such as the presence of dots and the at sign (@) to try to enforce some semblance of honesty. In many cases, the FTP server will accept a similar term such as guest or visitor. The point behind anonymous FTP is that users are not required to have a valid user ID or password on the remote system in order to be able to access files in some directories.

Of course, there are file areas on the FTP server that should only be accessed by authenticated users of the remote system. Private IDs can be combined with anonymous FTP to protect certain areas of the file system while allowing public access to others. Of course, this does not stop people from trying to access files they had no business seeing, but if the file system permissions are set up correctly (or at all), FTP is highly secure. However, the best way to prevent access to sensitive files is not to put them on an FTP server with public access in the first place.

The well-known port of the control connection is TCP port 21. The client runs the FTP client program and uses an ephemeral port to begin the interaction with the server. This connection asks for the user ID and password, anonymous or not, and is nothing more than a normal remote log-in session using the Telnet application.

Once logged in, the user is placed in a default file system directory. Navigation outside this directory might be permitted, but usually there’s a good reason to direct a user to this particular directory, and thus outside access should be unnecessary.

File transfer protocol

FTP as a protocol predates the public release of the Internet by decades. FTP stands for file transfer protocol. Prior to the hyperlinks present in our current WWW, FTP was the predominate method of transferring files from a place where it was stored on a server to a user’s computer. In fact FTP was designed prior to the current design of the IP addresses as we know it. File transfer is still in use as a method of transferring large files. The concept of FTP file transferring is in use in various Cloud services used throughout the Internet. The FTP protocol lets a client connect directly with an FTP server using port 20.4 The transfer of files through this connection is directly through the IP address and/or domain (Figure 3.16).

VI.B.3 File Transfer Protocol (FTP) and Telnet

File Transfer Protocol is one of the oldest Internet applications and is still widely used. First implemented for the ARPANET, the FTP was designed to transfer/copy files from one host to the other over the Internet. FTP first establishes a TCP connection between the two hosts and requests an authorization from the user. After the user supplies a valid user name and password, an FTP control session starts. Simple commands such as append, open, send, and rename are used to transfer files. The user can either supply these commands directly or a file transfer application program can be used. Data transfer can be done in two modes, binary and ASCII mode, allowing the transfer of text files as well as binary files such as executables, images, or video/audio files. One or more FTP connections can exist concurrently between any pair of computers.

The telnet application is used to log-on to a remote computer. It enables a user to access and work on a remote node as if the user were directly connected to that node.

III.A.4. FTP

File Transfer Protocol (FTP) is the method by which a specific computer transfers data or files around the Internet. Files can be simple text—usually known as ASCH files—or more complex data such as graphics or computer programs, known as binary files. The ability to pup down a file to get data or run a program (if the file is executable) is vital for people doing research and development work. The Internet transfers files at a rate of millions of bytes per second, and with the coming of the National Research and Education Network (NERN), that will soon be upgraded to gigabytes (thousands of millions of bytes) per second. FTP can do more than just retrieve files. It can be used to transfer files to remote machines from a given computer. To make it a practical tool, FTP includes commands of listing directories, listing files in directories, changing directories, getting information about what is being done, and setting parameters for how the operations will be done. Many pieces of free software can be obtained from around the Internet via anonymous FTPs, which allows users to log in to FTP sites where they do not have accounts. These anonymous FTP sites together contain millions of files that add up to terabytes of information.

FTP

The File Transfer Protocol (FTP) is used to transfer files to and from servers. Like Telnet, FTP has no confidentiality or integrity and should not be used to transfer sensitive data over insecure channels.

Note

When discussing insecure protocols such as Telnet and FTP, terms such as “no confidentiality” assume that they are used with default settings, with no additional hardening or encryption (such as using them via an IPsec VPN tunnel). You may mitigate the lack of confidentiality by using Telnet or FTP over an encrypted VPN tunnel or using SSH in their place, among other options. Also, “no integrity” means there is limited or no integrity at the application layer; some integrity may be provided at a lower layer, such as the transport layer.

FTP uses two ports: The control connection (where commands are sent) is TCP port 21, and Active FTP uses a data connection (where data is transferred) that originates from TCP port 20. Here are the two socket pairs (the next two examples use arbitrary ephemeral ports):

Client:1025 → Server:21 (control connection)

Server:20 → Client:1026 (data connection)

Notice that the data connection originates from the server, in the opposite direction of the control channel. This breaks the classic client–server data flow direction. Many firewalls will block the active FTP data connection for this reason, breaking Active FTP. Passive FTP addresses this issue by keeping all communication from client to server:

Client:1025 → Server:21 (control connection)

Client:1026 → Server:1025 (data connection)

The FTP server tells the client which listening data connection port to connect to; the client then makes a second connection. Passive FTP is more likely to pass through firewalls cleanly, as it flows in classic client–server direction.

FTP

The FTP is used to transfer files from one host to another, regardless of the hosts' physical locations. It is one of the oldest application layer protocols and was used on Advanced Research Projects (ARPANET) to transfer files from one mainframe to another. Still in use today, FTP is widely used on the Internet to transfer files. One of the problems with FTP is that it transmits users' passwords in clear text, so it is not a secure protocol.

In contrast to the single connections used by Network News Transfer Protocol (NNTP), HTTP, and SMTP, two separate connections are established for an FTP session. One transmits commands and replies, and the other transmits the actual data. The command and control information is sent, by default, via TCP port 21. The data, by default, is sent via TCP port 20.

Which protocol is not secure in transferring files?

Which of the following protocols transfers files without any authentication or security quizlet?

Which is the protocol that is used for secure file transfer?