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Understanding Binary Numbers

Because Why Not?

People tend to generally shy away from binary. As if there’s some automatic reaction to think only a math loving or crazy genius would even attempt to play with such an arcane form of a number system. Because that’s it ladies and gentleman, it is quite literally just another number system.

Do you remember when you were first taught your numbers from 1 – 10, probably not right? But you did. How about when it came to using these numbers in a constructed sort of manner alongside;

multiplication, addition, subtraction & devision

All of a sudden things started happening, objects could be quantified, time could be read and yet we were all still late for school! Lets dive in a little further and dispel this myth shall we?

So lets take 1 and 0, I personally like to think of it as either ‘ON : OFF‘ or ‘Alive : Dead‘. But you’re free to attribute as you wish! Moving on to the binary number;

10101101  = 173

What do you make of it? Exactly! It’s obviously 173. I mean how can anyone not see that, it’s as clear as day!

It turns out that while we were learning one way to count, we never ended up learning all the others. “Wait, don’t computers use numbers? Stop with your jibber jabber!”. Is what you could be thinking, and don’t you worry, you’re right. They’re just represented differently to the CPU’s, for performance and logistical reasons as well as hand full of other reasons I wont go into.

Below you’ll find different CPU’s architectures, alongside their integer specifications;

16 bit

  • Signed:  -32,768 (-1 x 215) through 32,767 (215 – 1)
  • Unsigned: 0 to 65,535 (216 – 1)

32 bit

  • Signed: -2,147,483,648 (-1 × 231) through 2,147,483,647 (231 – 1)
  • Unsigned: 0 to 4,294,967,295 (232 – 1)

64 bit

  • Signed: -9,223,372,036,854,775,808 (2^63) through 9,223,372,036,854,775,807 (2^63 − 1)
  • Unsigned: 0 to 18,446,744,073,709,551,615 (264 − 1

hello world: 01101000 01100101 01101100 01101100 01101111 00100000 01110111 01101111 01110010 01101100 01100100 – Click Here to test binary!

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[email protected] February 1, 2019 0 Comments
InternetSecuritySoftwareWeb Development

DVWA Lesson 2: Command execution (Low)

Good ol’ command execution

First Lesson: DVWA Lesson 1: Installing on Windows. Now we have everything set up on our Windows machine, we can finally begin we some fun! Login in with the password set during the previous lesson, and head towards the ‘DVWA Security’ tab on the bottom left hand side. Continue by setting the ‘Script Security’ level to ‘Low’, and clicking ‘submit’. If you’ve installed DVWA on Windows or Linux, keep in mind which when executing commands! Head over towards the ‘Command Execution’ tab:
  • Try entering ‘192.168.1.1’, what happens?
  • Are you able to execute any other commands?
  • No? Time to read the source, located at: DVWA-1.0.8/vulnerabilities/exec/source/low.php
<?php

if( isset( $_POST[ 'submit' ] ) ) {

$target = $_REQUEST[ 'ip' ];

// Determine OS and execute the ping command.
if (stristr(php_uname('s'), 'Windows NT')) {

$cmd = shell_exec( 'ping ' . $target );
$html .= '<pre>'.$cmd.'</pre>';

} else {

$cmd = shell_exec( 'ping -c 3 ' . $target );
$html .= '<pre>'.$cmd.'</pre>';

}

?>
As we can see, the $target variable contains our user input. Fortunately for us it’s not being sanitized when passed to the shell_exec function. Allowing for our commands to cause malicious behaviour. As we’re hosting DVWA on a Windows Operating System we’re able to run commands consecutively by using ‘&’ in-between each one. Try out the commands bellow, or your own, if you feel confident in a Windows Terminal environment. Examples
  • “127.0.0.1 & tasklist” – List the hosts current processes
  • “127.0.0.1 & netstat -a”- Gives us the current ports opened on the host
Further reading

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[email protected] August 21, 2015 0 Comments
InternetSecuritySoftwareWeb Development

DVWA Lesson 1: Installing on Windows

Damn vulnerable what?!

DVWA (Damn Vulnerable Web App) was made by security professionals, for researchers and enthusiasts to practice and learn different types of vulnerabilities in relation to web applications which can also be used for other things such as software activation keys. Before continuing it must be stressed that the testing of DVWA should be done on an isolated host with either VMware or Virtual Box, separated by a Host-only connection. This is for your safety, not doing so could lead to the compromise of your system. You can store the files on an external hard drive or a USB drive. You can purchase USB drives online from Amazon.


Software: Further reading: WARNING: THIS IS FOR EDUCATIONAL PURPOSES ONLY!
  • Firstly install Xampp for windows. Then continue on by opening up the Xampp Control Panel, either placed on your desktop, Program files or already started on the bottom left of the screen. Lastly, start your MySQL and Apache services.
  • Extract the dvwa folder to this location C:\xampp\htdocs\dvwa. We now open our webrowser and enter ‘localhost/dvwa’ (127.0.0.1/dvwa) into the url bar. If we are presented with a mysql.error() that means the database was unable to be created, but easily fixed in step 3.
  • Go on over to C:\xampp\htdocs\dvwa\config\config.inc.php and use your favourite editor to open the file, scroll down to line 20. We now enter the default PHPMyAdmin, in the db_password field, replacing the current one with nothing. Leaving it empty (no spaces)
  • Jump to your browser and go to 127.0.0.1/dvwa/setup.php, and click ‘create Database’ Then go to localhost/dvwa/login.php and enter your user name ‘admin’ and password ‘password’.
Next Lesson: DVWA Lesson 2: Command execution Low

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[email protected] August 21, 2015 0 Comments