I just found this video tutorial on cracking windowsXP password using ophcrack.
Looks good to me.
http://www.youtube.com/watch?v=VKgVisjlkYM

Here are some links to people search websites.I'm sure most of you know about them but I want other members to post links to some websites they know too.
http://www.411.com/
http://www.crimetime.com/
http://www.intelius.com/
http://www.peoplesearch.com/

I also got these links from my friends but couldn't really understand them.
http://www.paterva.com/maltego-classic.html
http://ssdi.rootsweb.com/
http://search.ancestry.com/

So any links you guys have?

Yes, cryptography is a must know if you are preparing for security+ and I believe it's a part of syllabus for CISSP too.

Frankly speaking I don't have much basic knowledge about hardware firewalls than I have about the software. But now that you have raised the question I'll learn more about them and edit my article in some days.

Thanks Kris I have now edited the links and they are working now.

Again, thanks all of you for taking the time to read it and for your comments

In simplest terms, cryptography is the science of transforming messages to make them more secure. The transformation is done using mathematical functions

The original message before undergoing transformation is called plaintext and after transformation is called cipher text.

The backbone of cryptography is the key. Simply put, key is a value upon which an algorithm operates.
And what's an algorithm?
I borrow this definition from another source.  The function or the formula of combining data and the key is called an algorithm

Data could be either the plain text or the cipher text.
So an encryption algorithm uses an encryption key and the plain text(data) to convert the plain text to cipher text and the decryption algorithm uses a decryption algorithm and the cipher text(data) to convert cipher text to plain text.

Plain text ----------->Encryption algo. -------------->Cipher text

Cipher text ---------->Decryption algo. -------------->Pain text


Cryptography algorithm can be broadly classified into:-
A: Symmetric or Secret key cryptography algo.
B: Asymmetric or Public key cryptography.

Always remember that symmetric key cryptography uses secret key and asymmetric key cryptography uses public and private keys.

Now let's explain these algorithms

SYMMETRIC KEY CRYPTOGRAPHY
In symmetric key cryptography the same secret key is used by both the sender and receiver.
Thus sender uses the secret key and an encryption algo. to encrypt the data and the receiver uses the same secret key and the decryption algo. to decrypt the data.
The decryption algo. is actually the opposite of encryption algo. in symmetric key cryptography.
The important thing to note here is that due complexity of algorithm there's no harm in making the algo. public(which, it usually is), thing to remain secret is the secret key.
If the attacker(Eve) somehow gets hold of the secret key he can easily decrypt the data sent by the sender.

Advantages of symmetric key cryptography.
The advantage of symmetric key cryptography is that it's fast in comparison to asymmetric key cryptography.

Disadvantages of symmetric key cryptography
Two major disadvantages of this algorithm are:
A: Each pair of users must have a unique secret key.
B: Key management i.e distribution of keys between the parties isn't easy.

Some examples of symmetric key cryptography are:
A: Substitutional algorithm
B: Transpositional algorithm
C: Block algorithm
D: Data Encryption standard i.e DES (Very important)

ASYMMETRIC KEY CRYPTOGRAPHY
In asymmetric key cryptography there are two keys: a private key and a public key.
The public key is available to the public and the private key is kept by receiver.
The public key is used for encryption and the private key is used for decryption.

Suppose S1 wants to send some data to R1 in encrypted form. S1 uses the public key of R1 which is available o the public and encrypts the data and sends it to R1. R1 uses it's private key to decrypt the data send by S1 and converts it to plain text.
Asymmetric key cryptography finds great use in digital signatures.

Advantages of asymmetric key cryptography
The advantage of asymmetric key cryptography is that it removes the restriction of a shared secret key between two entities.

Disadvantages of asymmetric key cryptography
The disadvantage of asymmetric key cryptography is that it's slow when compared to symmetric key cryptography.

Examples of asymmetric key cryptography
The most important eg. of asymmetric key cryptography is RSA named after its makers Rivest, Shamir and Adleman
Remember

Now I come to the end of this tutorial. I have tried my best to make it as easy to understand as possible. , it's just a basic tutorial, there's more to cryptography.

I don't ALWAYS recommend brute force.
Yes,you will recover the password but in how much time?
Just take this eg.
A 5 character password would be recovered instantly if we consider only lowercase letters but if there is a combination of both uppercase and lowercase it will take 12min to recover it.
A 7 character lowercase password will take 4 hrs. but a combination of uppercase and lowercase would devour 23 days of your life.
A 9 character lowercase takes 4 months and a combination of uppercase and lowercase would take 178 years to crack.
And I have not taken special characters in to consideration yet.

So according to me if you want to bruteforce choose a considerable amount of time and give it up if you couldn't crack the password in that time limit.

Reinstall is never a good option.You can go to whatthetech.com and post your problem in the Hijackthis log and malware removal section along with a Hijackthis log of the infected computer. They are great bunch of people and will surely help you out with your malware issues.

One of the most common question that I see in Security/Hacking forums is-Do I need an antivirus software?
The only answer I have to this question is-YES you do.
Regardless of whether you are a novice or a pro in the security field everyone needs an antivirus. Antivirus is obviously not your first line of defense (Firewalls are) but they are an integral part of your computer's security.
As a student for some time in malware removal courses I have seen and helped people who have been infected to the extent that they wouldn't even able to connect to the internet or faced regular computer crashes.90% of them are users who click every random pop-up that comes their way or download cracked software uploaded on random websites but the remaining 10% are users think they don't need any antivirus as they -according to them - know a lot about security and never click on pop-ups and test every software firstly on their virtual machines befor transferring it to their main desktop. But what these people forget is that antiviruses help in early detection of known malwares and a regular scan (I prefer one scan every fortnight) helps to check any subtle infection.

Of course, antiviruses don't help with every infection and with malwares like Antivirus 2007,8,9 series or cool web search you need specialized tools but antiviruses act as an external support to these tools and help in removal of remnants of these infections.

The other question that users ask after you convince them to use an antivirus is - Which is the best antivirus?
Well, there's a very thin line between an average and a good antivirus. And this thin line is often the scanning speed than malware detection. Most of the antiviruses don't have much difference in malware detection rate and like I earlier said antivirus softwares help in removal of small infections only, for some malwraes you need specialized tools. So, having any antivirus is better than having none.
There are some good free ones like  Avast , AVG and Avira antivir (Avast is my preference) and excellent commercial ones like Esset NOD32 and Kaspersky (I'm hearing some good reviews for the latest Norton antivirus too). The choice of using a free or a commercial antivirus depends on the user. I personally don't feel like spending my money over a commercial one if a free antivirus like Avast does almost the same job.

Now that I've written so much about antiviruses I think I should advertise the importance of firewalls, anti-spywares and hosts files too (Though I'll be writing a document on how to keep your computer safe in the coming days)

Firewalls -like I earlier said- are your first line of defense. They keep most of the pop-ups and hackers away. Windows firewall is a very basic firewall (No hard feelings microsoft). For better security you need a good firewall. An excellent free one is Comodo Firewall. Zone alarm is also a very good firewall though I would rather go for it's commercial one.

I won't dwell much in to anti-spyeares except giving links to some good ones. A combination of Spybot and a-squared is believed to be a good choice to go for. I personally use Spyware Terminator and never had any problems with it. There are also good commercial ones like Spyware doctor but I would rather choose a free one like the case in antivirus.

Lastly I would advice you to have a good hsts file. I'm using MVPS hosts file  which is the best hosts file available today. It block all pop-ups and random advertisements.And again it's free If you don't want to follow my advice on antivirus, firewalls and anti-spyware atleast go with the hosts file.

Using a good anivirus, firewall, anti-spyware and hosts file(MVPS) -preferably all free- along with a little common sense is enough to keep you computer safe.

And if you still get infected there's an excellent group of forums from  ASAP which help users with their malware issues and also train users in malware removal- all for free!

Now I just want you people to share you opinions with the rest of the community or just tell me was this useful. Any reply is greatly appreciated=P

Thanks everyone.
I actually didn't expect such a wonderful welcome. I see people here are willing to help other members.

Google- what else?

Thanks for tip COm BOY.
I have good command over DNS but I believe I need to work for DHCP.

Hello Everyone
I am Xen.
I'm presently studying Computer science engineering and want to become an IT security professional. I am currently studying a lot about ethical hacking and networking and enjoying each and every bit of it. The forum looks good and I think is the only forum I joined that has some actual professionals in this field. Guess I found a new home

Anyways I'm obviously not much knowledgeable like you people in the field of security but I hope to contribute to this site with whatever I know(Is posting tutorials aimed at beginners fine?)

Also I know some stuff related to malware and their removal so perhaps I could help there.

If you think  I'm missing something plz feel free to ask me anything you want. And sorry if I posted my intro in the wrong section, I'm still new and trying to get hold of the ambiance.

Regards,
Xen