Today, the number of Internet Service Providers (both free and the not so free ones) has really reached a very high figure. All of them aim at providing better services and making the process of connecting to the Internet easier for the user. One common practice amongst both Internet Service Providers and popular browsers like Internet Explorer, have this option called ‘Save Password’, which makes life easier for the user, as it allows the user to not type in the password each time he has to connect to the Internet.
Although, like all other software, as soon as the developer tries to add a user friendly feature or make the software easier to use or more efficient, he has to make at least some compromise in the security or safety field. One popular example would be Outlook Express, ever since the Preview Pane has been introduced within the email client, Outlook Express users have become prone to Email-Borne Viruses.
Anyway, getting back to the subject of this tutorial, even including the ‘Save Password’ feature has made the User’s Password unsafe. Now, what happens is that, when you check on this option or enable it, then the concerned software (Browser or Internet Service Provider Software) takes it passes it through an algorithm to encrypt it. Once, the Password is encrypted, it is then stored in the Windows Registry or in some .ini or .dat or a similar file. Now, this system sounds quite safe, however, if you look deeper, then you find that it is trouble waiting to happen.
The very fact that the encrypted password has to be stored somewhere, makes this feature vulnerable. Also, almostall software providing this feature does not use a strong algorithm. This makes the work of a hacker really easy. Some software even stores the password as plaintext in the registry!!! So, basically the weakest chain in this feature is that most software developers are weary of the fact that the encrypted password can be easily decrypted, once we study the software inside out. So, what I mean to say is that using this feature although surely makes life easy, for those of you who cannot remember passwords, but it does leave your Internet Account vulnerable. However, if you are one of those people who needs to write down your password on a piece of paper and stick it to the front of your monitor, then this feature is definitely for you.
So how do I crack the Netzero Dial Up Password?
Anyway, Netzero is a free ISP, which asks only for a advertising bar in return for Internet Access. It too provides this ‘Save Password’ feature, however, it too like most services, uses an extremely weak algorithm to encrypt the password. The following process of decryption works on Netzero version 3.0 and earlier and requires Win 9x, NT or Win 2K to be running.
For this exploit, you need to have local access to the machine, which has the Netzero software installed.
This vulnerability cannot be exploited unless and until you get the required file, for that you either have to have local access or need to devise a method of getting the file, which contains the password.
The Netzero Username and Password are stored in an ASCII file named, id.dat, which is located in the Netzero directory. If the user has enabled the ‘Save Password’ option, then the Username and Password are also stored in the jnetz.prop file. The passwords stored in both these files are encrypted using a very simply easy to crack algorithm. Although the algorithms used to get the encrypted information (to be stored in the two files), are not same, however they are derived from the same main algorithm. Both the algorithms differ very slightly. In this manual we will learn as to how this weak algorithm can be exploited.
The Netzero Password is encrypted using a substitution cipher system. The cipher system used is a typical example of a 1 to 1 mapping between characters where each single plaintext character is replaced by a single encrypted character.
Are you lost? Well, to understand better read about how the encryption is done in NetZero and how to decrypt.
[source: Ankit Fadia’s ‘what they don’t teach in manuals]
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