How to configure Outlook for Yahoo

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Applies to
Microsoft Office Outlook® 2003 Microsoft Outlook® 2002

You can use Outlook with many Yahoo! Mail e-mail accounts. However, free Web browser-based Yahoo! Mail accounts based in China, Taiwan, or the United States can only be used in Outlook if you have a paid subscription Yahoo! Mail account that includes POP3 access and forwarding.

You can receive your Yahoo! Mail e-mail messages by using Outlook from most places with an Internet connection. Yahoo! Mail provides you access to an authenticated SMTP server — allowing you to send e-mail messages using Outlook from your Yahoo! Mail account when you use another Internet service, such as at your office or when traveling.

Note Yahoo also provides mail services to partner Internet service providers (ISPs) (ISP: A business that provides access to the Internet for such things as electronic mail, chat rooms, or use of the World Wide Web. Some ISPs are multinational, offering access in many locations, while others are limited to a specific region.). All of these accounts can use be used with Outlook. See the chart at the end of this article to see if your e-mail account is included.

Do one of the following:

Add your Yahoo! Mail e-mail account

1. On the Tools menu, click E-mail Accounts.
2. Click Add a new e-mail account, and then click Next.
3. Click POP3, and then click Next.
4. Under User Information, do the following:
   1. In the Your Name box, type your full name the way that you want it to appear to other people.
   2. In the E-mail Address box, type your Member ID (or username), followed by the @ symbol and domain name.
5. Under Server Information, do the following:
   1. In the Incoming mail server (POP3) box, type the server name from the chart below that corresponds to your e-mail address.
   2. In the Outgoing mail server (SMTP) box, type the server name from the chart below that corresponds to your e-mail address.
6. Under Logon Information, do the following:
   1. In the User Name box, type your Yahoo Member ID (or username). Do not include the @ symbol or domain name.
   2. In the Password box, type your password.
   3. Select the Remember password check box.

      Note You have the option to have Outlook remember your password by typing it in the Password box and selecting the Remember password check box. Having Outlook remember your password means that you won't have to type your password each time you access the account; however, it also means that the account is vulnerable to anyone who has access to your computer.

      Use strong passwords that combine uppercase and lowercase letters, numbers, and symbols. Weak passwords don't mix these elements. Strong password: Y6dh!et5. Weak password: House27. Passwords should be 8 or more characters in length. A pass phrase that uses 14 or more characters is better. For more information, see Help protect your personal information with strong passwords.

      It is critical that you remember your password. If you forget your password, Microsoft cannot retrieve it. Store the passwords that you write down in a secure place away from the information that they help protect.

7. To verify that your account is working, click Test Account Settings. If there is missing or incorrect information, such as your password, you will be prompted to supply or correct it. Make sure your computer is connected to the Internet.
8. Click More Settings.
9. On the General tab, under Mail Account, type Yahoo! Mail.
10. Click the Outgoing Server tab, and then select the My outgoing server (SMTP) requires authentication check box.
11. Click Use same settings as my incoming mail server, and then click OK.
12. Click Next, and then click Finish.

Notes

• Do not select the Log on using Secure Password Authentication (SPA) check box.
• Unless specified by Yahoo! Mail, all server and address entries are typed in lowercase letters.

Remove your Yahoo! Mail e-mail account

1. On the Tools menu, click E-mail Accounts.
2. Click View or change existing e-mail accounts, and then click Next.
3. Click the Yahoo! Mail e-mail account that you want to remove, and then click Remove.
4. Click Finish.

How to trace an IP from an Email

Here’s a quick how-to guide on how you can track email to it’s originating location by figuring out the email’s IP address and looking it up. I have found this to be quite useful on many occasions for verification purposes since I receive lots of emails daily due to my blog. Tracking the IP address of an email sender does require looking at some technical details, so be ready to dig your heels in!

There are basically two steps involved in the process of tracking an email: find the IP address in the email header section and then look up the location of the IP address.

Finding the IP address of an email sender in GMail, Yahoo Mail, and Outlook

Let’s go ahead and take a look at how you would do this for Google, Yahoo and Outlook since those are the most popular email clients.

Google’s Gmail

1. Log into your account and open the email in question.

2. Click on the down arrow that’s to the right of the Reply link. Choose Show Original from the list.

Now here’s the technical part that I was telling you about earlier! You need to look for the lines of text that start with “Received: from“. It might be easier to simply press Cntrl + F and perform a search for that phase. You’ll notice that there are several Received From’s in the message header. This is because the message header contains the IP addresses of all of servers involved in routing that email to you.

To find the first computer that originally sent the email, you’ll have to find the Received From that’s farthest DOWN. As you can see from the above image, the first one is from a computer called “aseem” with the IP address 72.204.154.191. Then it was routed to my ISP’s server at eastrmmtao104.cox.net and so on and so forth till it got to your email server.

The computer aseem is my personal home computer and that’s my public IP address for my house! I’ll go through Yahoo and Outlook before talking about tracking the location of that IP address.

Yahoo Mail Beta

1. Log into your account and open the email (if you’re using Yahoo Mail Beta with the new preview interface, make sure you double-click on the email so that it opens in a new tab)

2. At the top right, you’ll see there is a drop-down option where Standard Header is selected by default.

3. Click on it and choose Full Header.

Again, you’ll see the same information as before, just in a different window:

Microsoft Outlook

1. Open the email in Outlook by double-clicking on it

2. Go to View at the top menu (the menu options for the email, not the main Outlook window) and choose Options.

You’ll get a dialog box where you can set the message options and at the bottom you’ll see the Internet Headers box. For some silly reason, the box is very small and you have to scroll a lot, so it’s best to simply copy and paste the text into Notepad to view it more easily.

Tracking the location of an IP address

Now that we have our originating IP address of 72.204.154.191, let’s find out where that is! You can do this by perform a location lookup on the IP address. My favorites are IP2Location and GeoBytes IP Locator.

GeoBytes gave me a big map of New Orleans, LA along with a bunch of other information about the location itself.

IP2Location also gave me the same information pretty much, including the ISP (Cox Communications). Of course, this is correct since I live in New Orleans!

If you want more information, you can do a WHOIS database search also. My favorite one is the ARIN WHOIS Database Search. This will give you information on who hosts that IP address and their registration information. You can always contact them to try and find more information on that particular IP address.

Have fun tracking down those emails! Questions, comments, or suggestions? Post a comment!

Auto End Tasks to Enable a Proper Shutdown

This reg file automatically ends tasks and timeouts that prevent programs from shutting down and clears the Paging File on Exit.

1. Copy the following (everything in the box) into notepad.


QUOTE
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management]
"ClearPageFileAtShutdown"=dword:00000001

[HKEY_USERS\.DEFAULT\Control Panel\Desktop]
"AutoEndTasks"="1"

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control]
"WaitToKillServiceTimeout"="1000"


2. Save the file as shutdown.reg
3. Double click the file to import into your registry.

NOTE: If your anti-virus software warns you of a "malicious" script, this is normal if you have "Script Safe" or similar technology enabled.

Anonymity

Anonymity

I can see you hiding in the shadows over there and so can the logs of all the web sites, FTP servers and other nooks and crannies you visit on the web. The sort of information gathered by these logs and which is available to the webmasters of the sites you visit include the address of the previous site you visited, your IP address, your computer's ID name, your physical location and the name of your ISP along with less personal details such as the operating system you're using and your screen resolution. If someone was snooping through your dustbin to gather information on consumer trends or tracking your every move to see where it is you go everyday you wouldn't be too chuffed would you. Well the web is no different, it's still an invasion of privacy and a threat to security and you don't have to put up with it.

Proxy servers:
Every time you visit a web site, detailed information about your system is automatically provided to the webmaster. This information can be used by hackers to exploit your computer or can be forwarded to the market research departments of consumer corporations who by tracking your activities on the internet are better equipped to direct more relevant spam at you. Your best defence against this is to use what is known as a proxy server, which will hide revealing information from the web sites you visit, allowing you to surf the web anonymously. These work by altering the way in which your browser retrieves web pages or connects to remote servers. With a proxy server set up, whenever you 'ask' IE or Netscape to look at a web page, the request is first sent through an external server which is completely independent of your ISP's servers. This third party server then does the requesting on your behalf so that it appears that the request came from them rather than you and your real IP address is never disclosed to the sites you visit. There is nothing to download and the whole process takes less than a minute.

There are two different ways to use proxy servers and both have their advantages and disadvantages. The first method is to use a web based service. What this involves is visiting the proxy's home page each time you want to browse a web site anonymously. The core component of such a system is the dialog box where you enter the address of the web site you want to visit. Each time you enter the URL of the site you want to browse via the proxy into this box, your personal information, IP address and so on is first encrypted before being sent to the site allowing you to maintain your anonymity. Two of the best examples of this type of web based proxy service are Code:
hxxp://www.rewebber.com/
and hxxp://www.anonymizer.com/.

Obviously one disadvantage of using a web based service like Rewebber or Anonymizer, however, is that you have to visit the proxies home page each time you want to surf anonymously. You could choose to select this page as your default home page, but it's still quite awkward if you're forever site hopping at the speed of light. The second main 'con' is that you often have to put up with extra adverts on the pages you visit. These are automatically inserted into the pages by the proxy - they have to pay for service somehow. More sophisticated and convenient solutions are also on offer yet they come with a price tag.

The second method you can use to protect your privacy via a proxy server involves adjusting the settings of your web browser so that you can surf anonymously without having to visit the home page of your proxy each time. To do this you will first need to know the name of your proxy server and the port number it uses. This information can be gleaned from either a public proxy server list or the FAQ referring to a private subscription based service. Once you have the name of the proxy server you wish to use, select 'Internet Options' from the 'Tools' menu of your browser. Now select 'Connections' followed by 'Settings' and tick the 'use a proxy server' check box. To finish the job all you have to do now is enter the name of the server in the 'address' box, the port which it uses in the 'port' box and go forth and surf anonymously.

Free, manual proxy servers as advertised on anonymity sites, if you can find one at all, are likely to be highly oversubscribed, and as a result the speed at which they retrieve web pages can deteriorate. In which case you can go in pursuit of a public proxy server list and select an alternative from it, which can then be set up manually. To locate such a list you can investigate sites such as Code:
hxxp://www.proxys4all.com/

however, this method isn't problem free either, so before you get too carried away and go jumping on the anonymity bandwagon there are a few things you should be aware of. It's very easy to use proxies to protect your privacy, but often the disadvantages of using them far out weigh the benefits. You see, the problem is that, like the proxy servers provided Rewebber et al, free, public proxies are nearly all over subscribed and so they can slow down web browsing considerably. Digging out fast reliable proxy servers is an art form in itself and is a skill which takes considerable practice. You could find a list of public proxy servers and then experiment with each one until you find one that runs at a reasonable speed, but this can be very time consuming and frustrating. Instead, your search would be much more efficient if you got a dedicated program to carry out this task for you. There are literally dozens of proxy seeking programs around which can do just that, and many of them are available as freeware. What these do is scan the internet for public proxy servers. These servers are then tested for speed and anonymity (not all of them are truly anonymous, even if they claim to be!) and once you find one which suits your requirements you can select it as your default proxy with the click of a button.

One of the most significant advantages of using an automated tool to locate proxy servers is that you do not have to keep editing your proxy settings manually each time you wish to try out a new one. Instead, what you do is enter 'localhost' or '127.0.0.1' into the 'address' box and '8088' into the 'port' box of your browser's proxy settings menu and then forget about it. All future proxy switching is then orchestrated from within your proxy seeking software, which subsequently relays the information to your browser or whatever type of application you are attempting to make anonymous. For those of you who are curious 'localhost' and the IP address '127.0.0.1' are the names by which every computer on the internet refers to itself.
Here's a good selection of links, which should help you to get started - Code:
hxxp://www.a4proxy.com/ Anonymity 4 Proxy
hxxp://www.helgasoft.com/hiproxy/ Hi Proxy
hxxp://www.proxy-verifier.com/ Proxy Verifier
hxxp://www.photono-software.de/ Stealther.

You may find that even when using these programs you have difficulty finding good proxy servers. It is for this reason that many people choose only to use proxy servers temporarily whilst doing something which may land them in trouble with their ISP, or in a worst case scenario with the law. The most obvious example of a situation in which you would want to cover your tracks is when scanning for public FTP servers and subsequently uploading to them. Most other net activities are unlikely to incur serious consequences so under these circumstances you can safely surf the web without a proxy. If you're really serious about protecting your privacy, however, your best bet is probably to invest in a dedicated, stable proxy such as the ones offered by Code:
hxxp://www.ultimate-anonymity.com/ Ultimate Anonymity


These aren't free, but may be worth the expense if you aren't keen on continuously switching proxy servers.

Before splashing out though it may be worth checking if your current ISP has a proxy server of its own which you can use. These aren't there to help you to commit cyber crimes and get away with it, they actually have a legitimate purpose as well - otherwise they wouldn't exist. You see, proxy servers were originally designed to help speed up web page loading times. Proxy servers contain a cache of all the web pages which have been requested via the browsers of the people using the proxy. When someone surfs the web using a proxy, the proxy first checks to see if it already has a copy of the web page stored in its cache. If this version of the page is bang up to date, it is sent to your computer and appears in your browser. If the page found in the cache of the proxy server is older than the one stored on the server hosting the page, a new request to the web server is made and the page is updated in the cache of the proxy before being sent to you. Because these servers use very fast internet connections they can retrieve web pages at much greater speeds than you can via your modest home setup. If these servers are located physically nearer to your home than the web host servers you wish to retrieve web pages from, the speed at which you browse the web will be accelerated.


Anonymity - Cookies
One last important point you need to be aware of before jumping in with both feet is that different programs have to be setup in different ways before being able to make external connections via a proxy server. For example, you can surf the web anonymously by modifying the settings in Internet Explorer or Netscape Navigator as explained earlier in this tutorial, but this will only affect your browser. If you then used Flash FXP to copy a batch of 0-day releases from one FTP server to another, this isn't going to protect you in the slightest. What you have to do is enter the name of the proxy server into each application you wish to make anonymous before making any external connections. This can usually be done by browsing through the preferences of your program to see if there is a 'use proxy server' option available. If there is, make sure you use it!


Cookies:
You have little to fear from the edible variety, but the digital ones can be a major threat to your security and privacy. A cookie is a tiny text file (usually less than 1kb in size), which is created and stored on your hard drive whenever you visit a dynamic (or an interactive if you like) web site. These are used to log your personal details so that you can access members only areas of web sites without having to type in a password every time, or to retain your customised settings so that they are available the next time you visit. If you're using a shared computer, anyone who visits the same site that you have previously logged in to can access your accounts. This is particularly worrying if you have entered your credit card details into a form on an e-commerce site. If your browser is set to automatically fill in these details whenever you
return to a previously visited site, this information could be clearly visible - you don't need me to explain the problems this could entail.

The solution to this problem is to delete any cookies which contain sensitive data once you have completed your transactions. Your cookies will be stored in a different place depending on which operating system you are using so you will have to use your detective skills to find them. As an example, in Windows XP they are located in your 'c:\Documents and Settings\Kylie Minogue\Cookies' directory (that is if your name is Kylie Minogue. Mine isn't in case you're wondering!). If you look in this directory, in some cases it is easy to identify which cookie is associated with which web site, but in other cases it's not so obvious. The cookie which was created when you visited Yahoo.com to check your email may be called kylie minogue@yahoo.txt for example. Unfortunately some cookies refer to the IP address of the site you visited and so look more like kylie minogue@145.147.25.21. These cookies can be selectively deleted one at a time if it's obvious which ones are causing a threat to your security, or you can just wipe out the whole lot in one fell swoop and have them recreated as and when they are required. However, if
you're really struggling to find your cookie jar, you could delete your cookies via your browser's tool bar instead. In Internet Explorer this can be done through the 'Tools' > 'Internet Options' menu items.

If all this sounds like too much hassle, you can always find a labour saving program which will be happy to take the job off your hands. These 'cookie crunching' programs allow you to be more selective when editing, viewing and deleting cookies from your system, and some of them will even prevent cookies from being created in the first place. Yes, I know you're hungry for links so I won't deprive you. Have a look here - Code:
hxxp://www.rbaworld.com/Programs/CookieCruncher/ Cookie
Cruncher
hxxp://www.thelimitsoft.com/ Cookie Crusher
hxxp://www.angove.com/ Cookie Killer
hxxp://www.kburra.com/ Cookie Pal
and
hxxp://www.cookiecentral.com/ Cookie Web Kit.

All about FTP

Setting Up A Ftp:


Well, since many of us have always wondered this, here it is. Long and drawn out. Also, before attempting this, realize one thing; You will have to give up your time, effort, bandwidth, and security to have a quality ftp server.
That being said, here it goes. First of all, find out if your IP (Internet Protocol) is static (not changing) or dynamic (changes everytime you log on). To do this, first consider the fact if you have a dial up modem. If you do, chances are about 999 999 out of 1 000 000 that your IP is dynamic. To make it static, just go to a place like h*tp://www.myftp.org/ to register for a static ip address.

You'll then need to get your IP. This can be done by doing this:
Going to Start -> Run -> winipcfg or www.ask.com and asking 'What is my IP?'

After doing so, you'll need to download an FTP server client. Personally, I'd recommend G6 FTP Server, Serv-U FTPor Bullitproof v2.15 all three of which are extremely reliable, and the norm of the ftp world.
You can download them on this site: h*tp://www.liaokai.com/softw_en/d_index.htm

First, you'll have to set up your ftp. For this guide, I will use step-by-step instructions for G6. First, you'll have to go into 'Setup -> General'. From here, type in your port # (default is 21). I recommend something unique, or something a bit larger (ex: 3069). If you want to, check the number of max users (this sets the amount of simultaneous maximum users on your server at once performing actions - The more on at once, the slower the connection and vice versa).

The below options are then chooseable:
-Launch with windows
-Activate FTP Server on Start-up
-Put into tray on startup
-Allow multiple instances
-Show "Loading..." status at startup
-Scan drive(s) at startup
-Confirm exit

You can do what you want with these, as they are pretty self explanatory. The scan drive feature is nice, as is the 2nd and the last option. From here, click the 'options' text on the left column.

To protect your server, you should check 'login check' and 'password check', 'Show relative path (a must!)', and any other options you feel you'll need. After doing so, click the 'advanced' text in the left column. You should then leave the buffer size on the default (unless of course you know what you're doing ), and then allow the type of ftp you want.

Uploading and downloading is usually good, but it's up to you if you want to allow uploads and/or downloads. For the server priority, that will determine how much conventional memory will be used and how much 'effort' will go into making your server run smoothly.

Anti-hammering is also good, as it prevents people from slowing down your speed. From here, click 'Log Options' from the left column. If you would like to see and record every single command and clutter up your screen, leave the defaults.

But, if you would like to see what is going on with the lowest possible space taken, click 'Screen' in the top column. You should then check off 'Log successful logins', and all of the options in the client directry, except 'Log directory changes'. After doing so, click 'Ok' in the bottom left corner.

You will then have to go into 'Setup -> User Accounts' (or ctrl & u). From here, you should click on the right most column, and right click. Choose 'Add', and choose the username(s) you would like people to have access to.

After giving a name (ex: themoonlanding), you will have to give them a set password in the bottom column (ex: wasfaked). For the 'Home IP' directory, (if you registered with a static server, check 'All IP Homes'. If your IP is static by default, choose your IP from the list. You will then have to right click in the very center column, and choose 'Add'.

From here, you will have to set the directory you want the people to have access to. After choosing the directory, I suggest you choose the options 'Read', 'List', and 'Subdirs', unless of course you know what you're doing . After doing so, make an 'upload' folder in the directory, and choose to 'add' this folder seperately to the center column. Choose 'write', 'append', 'make', 'list', and 'subdirs'. This will allow them to upload only to specific folders (your upload folder).

Now click on 'Miscellaneous' from the left column. Choose 'enable account', your time-out (how long it takes for people to remain idle before you automatically kick them off), the maximum number of users for this name, the maximum number of connections allowed simultaneously for one ip address, show relative path (a must!), and any other things at the bottom you'd like to have. Now click 'Ok'.
**Requested**


From this main menu, click the little boxing glove icon in the top corner, and right click and unchoose the hit-o-meter for both uploads and downloads (with this you can monitor IP activity). Now click the lightning bolt, and your server is now up and running.

Post your ftp info, like this:

213.10.93.141 (or something else, such as: 'f*p://example.getmyip.com')

User: *** (The username of the client)

Pass: *** (The password)

Port: *** (The port number you chose)

So make a FTP and join the FTP section


Listing The Contents Of A Ftp:

Listing the content of a FTP is very simple.
You will need FTP Content Maker, which can be downloaded from here:
ht*p://www.etplanet.com/download/application/FTP%20Content%20Maker%201.02.zip

1. Put in the IP of the server. Do not put "ftp://" or a "/" because it will not work if you do so.
2. Put in the port. If the port is the default number, 21, you do not have to enter it.
3. Put in the username and password in the appropriate fields. If the login is anonymous, you do not have to enter it.
4. If you want to list a specific directory of the FTP, place it in the directory field. Otherwise, do not enter anything in the directory field.
5. Click "Take the List!"
6. After the list has been taken, click the UBB output tab, and copy and paste to wherever you want it.


If FTP Content Maker is not working, it is probably because the server does not utilize Serv-U Software.

If you get this error message:
StatusCode = 550
LastResponse was : 'Unable to open local file test-ftp'
Error = 550 (Unable to open local file test-ftp)
Error = Unable to open local file test-ftp = 550
Close and restart FTP Content Maker, then try again.




error messages:

110 Restart marker reply. In this case, the text is exact and not left to the particular implementation; it must read: MARK yyyy = mmmm Where yyyy is User-process data stream marker, and mmmm server's equivalent marker (note the spaces between markers and "=").
120 Service ready in nnn minutes.
125 Data connection already open; transfer starting.
150 File status okay; about to open data connection.
200 Command okay.
202 Command not implemented, superfluous at this site.
211 System status, or system help reply.
212 Directory status.
213 File status.
214 Help message. On how to use the server or the meaning of a particular non-standard command. This reply is useful only to the human user.
215 NAME system type. Where NAME is an official system name from the list in the Assigned Numbers document.
220 Service ready for new user.
221 Service closing control connection. Logged out if appropriate.
225 Data connection open; no transfer in progress.
226 Closing data connection. Requested file action successful (for example, file transfer or file abort).
227 Entering Passive Mode (h1,h2,h3,h4,p1,p2).
230 User logged in, proceed.
250 Requested file action okay, completed.
257 "PATHNAME" created.
331 User name okay, need password.
332 Need account for login.
350 Requested file action pending further information.
421 Too many users logged to the same account
425 Can't open data connection.
426 Connection closed; transfer aborted.
450 Requested file action not taken. File unavailable (e.g., file busy).
451 Requested action aborted: local error in processing.
452 Requested action not taken. Insufficient storage space in system.
500 Syntax error, command unrecognized. This may include errors such as command line too long.
501 Syntax error in parameters or arguments.
502 Command not implemented.
503 Bad sequence of commands.
504 Command not implemented for that parameter.
530 Not logged in.
532 Need account for storing files.
550 Requested action not taken. File unavailable (e.g., file not found, no access).
551 Requested action aborted: page type unknown.
552 Requested file action aborted. Exceeded storage allocation (for current directory or dataset).
553 Requested action not taken. File name not allowed.


Active FTP vs. Passive FTP, a Definitive Explanation

Introduction
One of the most commonly seen questions when dealing with firewalls and other Internet connectivity issues is the difference between active and passive FTP and how best to support either or both of them. Hopefully the following text will help to clear up some of the confusion over how to support FTP in a firewalled environment.

This may not be the definitive explanation, as the title claims, however, I've heard enough good feedback and seen this document linked in enough places to know that quite a few people have found it to be useful. I am always looking for ways to improve things though, and if you find something that is not quite clear or needs more explanation, please let me know! Recent additions to this document include the examples of both active and passive command line FTP sessions. These session examples should help make things a bit clearer. They also provide a nice picture into what goes on behind the scenes during an FTP session. Now, on to the information...



The Basics
FTP is a TCP based service exclusively. There is no UDP component to FTP. FTP is an unusual service in that it utilizes two ports, a 'data' port and a 'command' port (also known as the control port). Traditionally these are port 21 for the command port and port 20 for the data port. The confusion begins however, when we find that depending on the mode, the data port is not always on port 20.



Active FTP
In active mode FTP the client connects from a random unprivileged port (N > 1024) to the FTP server's command port, port 21. Then, the client starts listening to port N+1 and sends the FTP command PORT N+1 to the FTP server. The server will then connect back to the client's specified data port from its local data port, which is port 20.

From the server-side firewall's standpoint, to support active mode FTP the following communication channels need to be opened:

FTP server's port 21 from anywhere (Client initiates connection)
FTP server's port 21 to ports > 1024 (Server responds to client's control port)
FTP server's port 20 to ports > 1024 (Server initiates data connection to client's data port)
FTP server's port 20 from ports > 1024 (Client sends ACKs to server's data port)


In step 1, the client's command port contacts the server's command port and sends the command PORT 1027. The server then sends an ACK back to the client's command port in step 2. In step 3 the server initiates a connection on its local data port to the data port the client specified earlier. Finally, the client sends an ACK back as shown in step 4.

The main problem with active mode FTP actually falls on the client side. The FTP client doesn't make the actual connection to the data port of the server--it simply tells the server what port it is listening on and the server connects back to the specified port on the client. From the client side firewall this appears to be an outside system initiating a connection to an internal client--something that is usually blocked.



Active FTP Example
Below is an actual example of an active FTP session. The only things that have been changed are the server names, IP addresses, and user names. In this example an FTP session is initiated from testbox1.slacksite.com (192.168.150.80), a linux box running the standard FTP command line client, to testbox2.slacksite.com (192.168.150.90), a linux box running ProFTPd 1.2.2RC2. The debugging (-d) flag is used with the FTP client to show what is going on behind the scenes. Everything in red is the debugging output which shows the actual FTP commands being sent to the server and the responses generated from those commands. Normal server output is shown in black, and user input is in bold.

There are a few interesting things to consider about this dialog. Notice that when the PORT command is issued, it specifies a port on the client (192.168.150.80) system, rather than the server. We will see the opposite behavior when we use passive FTP. While we are on the subject, a quick note about the format of the PORT command. As you can see in the example below it is formatted as a series of six numbers separated by commas. The first four octets are the IP address while the second two octets comprise the port that will be used for the data connection. To find the actual port multiply the fifth octet by 256 and then add the sixth octet to the total. Thus in the example below the port number is ( (14*256) + 178), or 3762. A quick check with netstat should confirm this information.

testbox1: {/home/p-t/slacker/public_html} % ftp -d testbox2
Connected to testbox2.slacksite.com.
220 testbox2.slacksite.com FTP server ready.
Name (testbox2:slacker): slacker
---> USER slacker
331 Password required for slacker.
Password: TmpPass
---> PASS XXXX
230 User slacker logged in.
---> SYST
215 UNIX Type: L8
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
ftp: setsockopt (ignored): Permission denied
---> PORT 192,168,150,80,14,178
200 PORT command successful.
---> LIST
150 Opening ASCII mode data connection for file list.
drwx------ 3 slacker users 104 Jul 27 01:45 public_html
226 Transfer complete.
ftp> quit
---> QUIT
221 Goodbye.


Passive FTP
In order to resolve the issue of the server initiating the connection to the client a different method for FTP connections was developed. This was known as passive mode, or PASV, after the command used by the client to tell the server it is in passive mode.

In passive mode FTP the client initiates both connections to the server, solving the problem of firewalls filtering the incoming data port connection to the client from the server. When opening an FTP connection, the client opens two random unprivileged ports locally (N > 1024 and N+1). The first port contacts the server on port 21, but instead of then issuing a PORT command and allowing the server to connect back to its data port, the client will issue the PASV command. The result of this is that the server then opens a random unprivileged port (P > 1024) and sends the PORT P command back to the client. The client then initiates the connection from port N+1 to port P on the server to transfer data.

From the server-side firewall's standpoint, to support passive mode FTP the following communication channels need to be opened:

FTP server's port 21 from anywhere (Client initiates connection)
FTP server's port 21 to ports > 1024 (Server responds to client's control port)
FTP server's ports > 1024 from anywhere (Client initiates data connection to random port specified by server)
FTP server's ports > 1024 to remote ports > 1024 (Server sends ACKs (and data) to client's data port)



In step 1, the client contacts the server on the command port and issues the PASV command. The server then replies in step 2 with PORT 2024, telling the client which port it is listening to for the data connection. In step 3 the client then initiates the data connection from its data port to the specified server data port. Finally, the server sends back an ACK in step 4 to the client's data port.

While passive mode FTP solves many of the problems from the client side, it opens up a whole range of problems on the server side. The biggest issue is the need to allow any remote connection to high numbered ports on the server. Fortunately, many FTP daemons, including the popular WU-FTPD allow the administrator to specify a range of ports which the FTP server will use. See Appendix 1 for more information.

The second issue involves supporting and troubleshooting clients which do (or do not) support passive mode. As an example, the command line FTP utility provided with Solaris does not support passive mode, necessitating a third-party FTP client, such as ncftp.

With the massive popularity of the World Wide Web, many people prefer to use their web browser as an FTP client. Most browsers only support passive mode when accessing ftp:// URLs. This can either be good or bad depending on what the servers and firewalls are configured to support.



Passive FTP Example
Below is an actual example of a passive FTP session. The only things that have been changed are the server names, IP addresses, and user names. In this example an FTP session is initiated from testbox1.slacksite.com (192.168.150.80), a linux box running the standard FTP command line client, to testbox2.slacksite.com (192.168.150.90), a linux box running ProFTPd 1.2.2RC2. The debugging (-d) flag is used with the FTP client to show what is going on behind the scenes. Everything in red is the debugging output which shows the actual FTP commands being sent to the server and the responses generated from those commands. Normal server output is shown in black, and user input is in bold.

Notice the difference in the PORT command in this example as opposed to the active FTP example. Here, we see a port being opened on the server (192.168.150.90) system, rather than the client. See the discussion about the format of the PORT command above, in the Active FTP Example section.

testbox1: {/home/p-t/slacker/public_html} % ftp -d testbox2
Connected to testbox2.slacksite.com.
220 testbox2.slacksite.com FTP server ready.
Name (testbox2:slacker): slacker
---> USER slacker
331 Password required for slacker.
Password: TmpPass
---> PASS XXXX
230 User slacker logged in.
---> SYST
215 UNIX Type: L8
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> passive
Passive mode on.
ftp> ls
ftp: setsockopt (ignored): Permission denied
---> PASV
227 Entering Passive Mode (192,168,150,90,195,149).
---> LIST
150 Opening ASCII mode data connection for file list
drwx------ 3 slacker users 104 Jul 27 01:45 public_html
226 Transfer complete.
ftp> quit
---> QUIT
221 Goodbye.


Summary
The following chart should help admins remember how each FTP mode works:

Active FTP :
command : client >1024 -> server 21
data : client >1024 <- server 20 Passive FTP : command : client >1024 -> server 21
data : client >1024 -> server >1024

A quick summary of the pros and cons of active vs. passive FTP is also in order:

Active FTP is beneficial to the FTP server admin, but detrimental to the client side admin. The FTP server attempts to make connections to random high ports on the client, which would almost certainly be blocked by a firewall on the client side. Passive FTP is beneficial to the client, but detrimental to the FTP server admin. The client will make both connections to the server, but one of them will be to a random high port, which would almost certainly be blocked by a firewall on the server side.

Luckily, there is somewhat of a compromise. Since admins running FTP servers will need to make their servers accessible to the greatest number of clients, they will almost certainly need to support passive FTP. The exposure of high level ports on the server can be minimized by specifying a limited port range for the FTP server to use. Thus, everything except for this range of ports can be firewalled on the server side. While this doesn't eliminate all risk to the server, it decreases it tremendously.