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/*Pointer Basics: Creating and Using Pointers*/
#include<stdio.h>
int main(void){
int number = 100;
int *pt = &number;
printf("Value of 'number' is: %d", number);
printf("Address of 'number' is: %p", pt);
*pt = 200;
printf("New value of 'number' is: %d", number);
return 0;
}
/*Pointer Basics Part 1: Program 2*/
#include<stdio.h>
int main(void){
int var = 10;
int *pt = &var;
printf("The Value of 'var' is: %d\n", var);
printf("De-referencing: *pt = %d\n", *pt);
printf("Ampersand: The Address of 'var' is %p\n", &var);
printf("pt = %p\n", pt);
return 0;
}
Password cracking is the process of attempting to gain Unauthorized access to restricted systems using common passwords or algorithms that guess passwords. In other words, it's an art of obtaining the correct password that gives access to a system protected by an authentication method.
Password cracking employs a number of techniques to achieve its goals. The cracking process can involve either comparing stored passwords against word list or use algorithms to generate passwords that match
In this Tutorial, we will introduce you to the common password cracking techniques and the countermeasures you can implement to protect systems against such attacks.
Password strength is the measure of a password's efficiency to resist password cracking attacks. The strength of a password is determined by;
Let's now look at a practical example. We will use three passwords namely
1. password
2. password1
3. #password1$
For this example, we will use the password strength indicator of Cpanel when creating passwords. The images below show the password strengths of each of the above-listed passwords.
Note: the password used is password the strength is 1, and it's very weak.
Note: the password used is password1 the strength is 28, and it's still weak.
Note: The password used is #password1$ the strength is 60 and it's strong.
The higher the strength number, better the password.
Let's suppose that we have to store our above passwords using md5 encryption. We will use an online md5 hash generator to convert our passwords into md5 hashes.
The table below shows the password hashes
| Password | MD5 Hash | Cpanel Strength Indicator |
|---|---|---|
| password | 5f4dcc3b5aa765d61d8327deb882cf99 | 1 |
| password1 | 7c6a180b36896a0a8c02787eeafb0e4c | 28 |
| #password1$ | 29e08fb7103c327d68327f23d8d9256c | 60 |
We will now use http://www.md5this.com/ to crack the above hashes. The images below show the password cracking results for the above passwords.
As you can see from the above results, we managed to crack the first and second passwords that had lower strength numbers. We didn't manage to crack the third password which was longer, complex and unpredictable. It had a higher strength number.
There are a number of techniques that can be used to crack passwords. We will describe the most commonly used ones below;
Spidering sample dictionary attack wordlist
1976 <founder birth year>
smith jones <founder name>
acme <company name/initials>
built|to|last <words in company vision/mission>
golfing|chess|soccer <founders hobbies
These are software programs that are used to crack user passwords. We already looked at a similar tool in the above example on password strengths. The website www.md5this.com uses a rainbow table to crack passwords. We will now look at some of the commonly used tools
John the Ripper
John the Ripper uses the command prompt to crack passwords. This makes it suitable for advanced users who are comfortable working with commands. It uses to wordlist to crack passwords. The program is free, but the word list has to be bought. It has free alternative word lists that you can use. Visit the product website http://www.openwall.com/john/ for more information and how to use it.
Cain & Abel
Cain & Abel runs on windows. It is used to recover passwords for user accounts, recovery of Microsoft Access passwords; networking sniffing, etc. Unlike John the Ripper, Cain & Abel uses a graphic user interface. It is very common among newbies and script kiddies because of its simplicity of use. Visit the product website http://www.softpedia.com/get/Security/Decrypting-Decoding/Cain-and-Abel.shtml for more information and how to use it.
Ophcrack
Ophcrack is a cross-platform Windows password cracker that uses rainbow tables to crack passwords. It runs on Windows, Linux and Mac OS. It also has a module for brute force attacks among other features. Visit the product website http://ophcrack.sourceforge.net/ for more information and how to use it.
In this practical scenario, we are going to crack Windows account with a simple password. Windows uses NTLM hashes to encrypt passwords. We will use the NTLM cracker tool in Cain and Abel to do that.
Cain and Abel cracker can be used to crack passwords using;
We will use the dictionary attack in this example. You will need to download the dictionary attack wordlist here 10k-Most-Common.zip
For this demonstration, we have created an account called Accounts with the password qwerty on Windows 7.
