Category: Computers

Posted on

How to extract Audio from Youtube Flash Video (FLV) in Ubuntu Linux

First you need youtube-dl tool or ‘cclive’ to download the Youtube .FLV file.

Then, download the Youtube stream.
python youtube-dl http://www.youtube.com/watch?v=lee7a55401e

Alternatively, you can use ‘cclive’ to download the youtube stream.
cclive http://www.youtube.com/watch?v=lee7a55401e

After that, use ffmpeg to extract the audio and encode it to MP3
ffmpeg -i lee7a55401e.flv vn -acodec libmp3lame -ab 128000 -ar 44100 lee7a55401e.mp3

Note: You need to install the restricted codecs in order to extract MP3 audio files.

Thanks Mohammad Bahathir Hashim for the tip!

Posted on

How to limit MySQL port access to specific network

MySQL service port are not meant to be accessible to the outside world as it would become a security concern to the administrator.

Although MySQL server (mysqld) by itself has a built-in mechanism to deny access from unauthorized ip-address, it still does not protect it from being overwhelmed by multiple malicious requests or buffer overflow attack directed to the server.

One of the solution is to limit the MySQL port access to trusted network using iptables

This assume your trusted network has the address within the range of 192.168.1.1-192.168.1.254


iptables -A INPUT -i eth0 -p tcp -s 192.168.1.0/24 --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp --sport 3306 -m state --state ESTABLISHED -j ACCEPT

MySQL server (mysqld) uses port 3306.

Note: Always assume the internet as the untrusted network!

Posted on

Ubuntu 11.10 drops Synaptic package manager

The upcoming Ubuntu 11.10 release (Oneiric Ocelot) will drop Synaptic Package Manager from default installation in favor of Ubuntu Software Center.

This has been foreseen since Canonical has spend their effort in developing and improving Ubuntu Software Center as a convenience one-stop center to install free and paid software alike.

Personal Thoughts
Personally, I still prefer to use Synaptic Package Manager over Ubuntu Software Center as it is still doesn’t offer the same number of options that I used to get from Synaptic (ability to search by name, description, ability to test the fastest mirror).

But I believe the changes that Canonical and Ubuntu community made might make it easier to streamline the looks and functionality of package manager into desktop environment (Unity) regardless of the computing platform.

Synaptic

Posted on

How to make sudo display funny error messages in Ubuntu Linux

sudo is probably the most used command in Ubuntu.

In this post, I will show you how to make ‘sudo’ display funny and humorous error messages in Ubuntu Linux.

To do that, you would only need to edit the /etc/sudoers :

sudo nano /etc/sudoers

Then find the line that starts with Defaults env_reset, add insults at the end of the line so it would look like this:

# See the man page for details on how to write a sudoers file
#
Defaults env_reset, insults

Save the file, and you are done! You can test the results by running the sudo command and entering the wrong password.

Screenshot Demo

sudo insults

Posted on

How to crack SHA1, MD5 and Windows NTLM password hash using Rainbow tables in Linux

Rainbow tables is a form of attack method used to crack stored cryptographic hashes commonly used as passwords in various application.

It is similar to brute-force and dictionary attack that it will try to compare the resulting hash with the hash it attempts to crack, except in Rainbow tables, the possible matching hashes are all precomputed before hand, and it uses reduction function to double the lookup speeds at the expense of the storage space (time vs space trade off).

Project Rainbow-Crack offer downloadable binaries (free but not opensource) for GNU / Linux and Microsoft Windows operating system. The application package comes with several tools that can help in generating (rtgen), sorting (rtsort) and cracking (rcrack) sha1,md5 and NTLM hashes.

How to use rtgen, rtsort and rcrack ?
First before starting to crack sha1 hashes, we need to generate rainbow table with rtgen.
rtgen

rtgen sha1 loweralpha-numeric 1 8 0 5000 6553600 0

Usage:
rtgen <hash type> <loweralpha | loweralpha-numeric | numeric | mixalpha-numeric| alpha-numeric> <min length> <max length> <table_index> <chain_len> <chain_num> <part_index>

rtsort
Then we need to use rtsort to sort the rainbow tables generated by rtgen.

rtsort *.rt

rcrack
Finally run rcrack to crack the hashes

rcrack *.rt -l hash1.txt

or


rcrack *.rt -h af8978b1797b72acfff9595a5a2a373ec3d9106d

crack process

For more examples to generate and use rainbow tables, please refer to Project Rainbow-Table Example