[JASJAR, XDA Exec, MDA Pro General] ZeBoxx:
N2h, you're being rather rude, so I would have expected a lot more "you don't need one" replies by now just to spite you. I'll answer your question first, and then detail why I believe you're being rather rude.

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What you're asking about isn't really a firewall. A firewall is used to prevent certain communications either coming into a machine, or going out of it. E.g. a firewall could be placed on outbound port 80 to prevent users from browsing 99% of the web, or a firewall can and should be placed on inbound port 139 to stop some older netbios 'attacks'.

What you're really asking about is whether the communication you do via your PocketPC - over wifi - is 'secure' in that others can't access your information. The answer to that isn't a simple yes/no - it will depend on a few things.

The first thing to make sure as that the access point you're using has WEP (Wireless Encryption Protocol) enabled. The bigger the key, the better. This will mean that 'over the air', your information will be encrypted. Anybody who would 'snoop' that information from the air will need a LOT of data, and a reasonably fast machine, to get the WEP key.

The next thing to make sure is that if the information you're sending is rather sensitive, that you send this information to a site which is using SSL. SSL encrypts your data on your PocketPC itself, all the way through the WiFi router/access point, over the internet, bouncing off of satellites - whatever, until it reaches the destination website where the data is decrypted again. The odds of anybody cracking that signal are *very* slim. It can be done, but it takes ages and ages on multiple computers for even the simplest of SSL encryptions. The 'dumb' way to check whether the site uses SSL is to see if the URL starts with "https". The 'proper' way is to check if the padlock icon is 'locked' in PIE (left of the address bar).

The third thing, if you're using e-mail, is to use an e-mail encryption application, such as PGP. I'm not aware if any exist for PocketPC, but I'm sure they do. These basically encrypt your message in a way that it can still be sent by plain e-mail. The recipient then decrypts the message again on their end. Based on the encryption method used and the length of the message, it would take quantum computers to decrypt it to anything meaningful.

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For those wondering whether you do indeed need a Firewall - no, you don't. You may wish to look into some basic BlueTooth protection if you leave that on a lot, but other than that there are no real intrusion points for a PocketPC that you'd have to be worried about.

Microsoft may turn the PocketPC into some ueberplatform in the future which would make it more vulnerable, or maybe they learned their lesson and they'll keep things fairly secure - who knows.

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Now then.. as to why you're being rude...

First.. your post - what's with the bold blue text? Do you think it would get people's attention easier? Just makes it more difficult to read.

Second... you address a specific person, vijay555 - who is a very busy person. But even if he wasn't, it's a bit presumptious of you that 1. he would be reading this, 2. he would be interested in replying at all.

Third... you presume that people would go off-topic, in your original post (in large red type, at that). Why not have a bit more faith in fellow man and see what replies roll in, first? Then if people go off-topic, point it out and ask that they try and address the issue you raised in your post.

Fourth... when somebody does answer your post, even if it is a rather short reply, you tell them to either post a better reply, or not reply at all. Don't be surprised if many people will interpret this in a way that will make them not want to reply to any of your posts at all.

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Edit: and such is the cost of typing long replies - other people reply before you ;)