Social Networking Sites

Written by Pravin on October 24, 2008 – 6:54 am -

Social networking sites are building huge online communites of people  sharing interests & activities.  Social networking sites allows individuals to meet strangers which makes it unique.  After joining a social network site, users are prompted to identify others in the system with whom they have a relationship. The label for these relationships differs depending on the site—popular terms include “Friends,” “Contacts,” and “Fans.” Most SNSs also provide a mechanism for users to leave messages on their Friends’ profiles. This feature typically involves leaving “comments,” although sites employ various labels for this feature. In addition, SNSs often have a private messaging feature similar to webmail. While both private messages and comments are popular on most of the major SNSs, they are not universally available.

Social networking has created new ways to communicate and share information. Social networking websites are being used regularly by millions of people, and it now seems that social networking will be an enduring part of everyday life.

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Written by Pravin on October 20, 2008 – 6:23 am -

OSSEC is a scalable, multi-platform, open source Host-based Intrusion Detection System (HIDS). It has a powerful correlation and analysis engine, integrating log analysis, file integrity checking, Windows registry monitoring, centralized policy enforcement, rootkit detection, real-time alerting and active response. It runs on most operating systems, including Linux, OpenBSD, FreeBSD, MacOS, Solaris and Windows.

Installing OSSEC on Linux:

cd /tmp
tar xvfz ossec-hids-0.9-1a.tar.gz

Then we run the installation script:

cd ossec-hids-0.9-1a

The installation script will ask you a few questions:

** Para instalação em português, escolha [br].
** Fur eine deutsche Installation wohlen Sie [de].
** For installation in English, choose [en].
** Para instalar en Español , eliga [es].
** Pour une installation en français, choisissez [fr]
** Per l’installazione in Italiano, scegli [it].
** æ¥æ¬èªã§ã¤ã³ã¹ãã¼ã«ãã¾ãï¼é¸æãã¦ä¸ãã
** Aby instalowaÄ w jÄzyku Polskim, wybierz [pl].
** ÐÐ»Ñ Ð¸Ð½ÑÑÑÑкÑий по ÑÑÑановке на ÑÑÑÑком ,введиÑе [ru].
** Türkçe kurulum için seçin [tr].
(en/br/de/es/fr/it/jp/pl/ru/tr) [en]: <– en (or one of the other options, if you don’t want to use English)

OSSEC HIDS v0.9-1 Installation Script –

You are about to start the installation process of the OSSEC HIDS.
You must have a C compiler pre-installed in your system.
If you have any questions or comments, please send an e-mail
to (or

- System: Linux 2.6.8-2-386
- User: root
- Host:

— Press ENTER to continue or Ctrl-C to abort. – <– [ENTER]

1- What kind of installation do you want (server, agent, local or help)? <– local

- Choose where to install the OSSEC HIDS [/var/ossec]: <– /var/ossec

3.1- Do you want e-mail notification? (y/n) [y]: <– y

- What’s your e-mail address? <– (please enter your own email address here)

- We found your SMTP server as:
- Do you want to use it? (y/n) [y]:
<– y (normally you can accept the installer’s proposal, unless you want to use another SMTP server)

3.2- Do you want to run the integrity check daemon? (y/n) [y]: <– y

3.3- Do you want to run the rootkit detection engine? (y/n) [y]: <– y

- Do you want to enable active response? (y/n) [y]: <–y

- Do you want to enable the firewall-drop response? (y/n) [y]: <– y

- Do you want to add more IPs to the white list? (y/n)? [n]: <– n (unless you want to whitelist more IP addresses)

3.6- Setting the configuration to analyze the following logs:
– /var/log/messages
– /var/log/auth.log
– /var/log/syslog
– /var/log/

- If you want to monitor any other file, just change
the ossec.conf and add a new localfile entry.
Any questions about the configuration can be answered
by visiting us online at .

— Press ENTER to continue — <– [ENTER]

- System is Linux (SysV).
- Init script modified to start OSSEC HIDS during boot.
Adding system startup for /etc/init.d/ossec …
/etc/rc0.d/K20ossec -> ../init.d/ossec
/etc/rc1.d/K20ossec -> ../init.d/ossec
/etc/rc6.d/K20ossec -> ../init.d/ossec
/etc/rc2.d/S20ossec -> ../init.d/ossec
/etc/rc3.d/S20ossec -> ../init.d/ossec
/etc/rc4.d/S20ossec -> ../init.d/ossec
/etc/rc5.d/S20ossec -> ../init.d/ossec

- Configuration finished properly.

- To start OSSEC HIDS:
/var/ossec/bin/ossec-control start

- To stop OSSEC HIDS:
/var/ossec/bin/ossec-control stop

- The configuration can be viewed or modified at /var/ossec/etc/ossec.conf

Thanks for using the OSSEC HIDS.
If you have any question, suggestion or if you find any bug,
contact us at or using our public maillist at

More information can be found at

— Press ENTER to finish (maybe more information below). — <– [ENTER]

That’s it, OSSEC HIDS is now installed and ready to be started.

Starting And Running OSSEC HIDS:

In order to start OSSEC HIDS, we run this command:

/etc/init.d/ossec start

The output should look like this:

server1:/etc/init.d# /etc/init.d/ossec start
Starting OSSEC HIDS v0.9-1 (by Daniel B. Cid)…
Started ossec-maild…
Started ossec-execd…
Started ossec-analysisd…
Started ossec-logcollector…
Started ossec-syscheckd…

As you might have seen during OSSEC HIDS installation, the installer also created the necessary system startup links for OSSEC HIDS, so that OSSEC HIDS will be started automatically whenever you boot/reboot your system.

After OSSEC HIDS has been started, it will run silently in the background, performing log analysis, integrity checking, rootkit detection, etc. You can check that it’s running by executing

ps aux

In the output you should find something like this:

ossecm    2038  0.0  0.4  1860  792 ?        S    12:40   0:00 /var/ossec/bin/ossec-maild root      2042  0.0  0.3  1736  648 ?        S    12:40   0:00 /var/ossec/bin/ossec-execd ossec     2046  0.2  0.5  2192 1136 ?        S    12:40   0:00 /var/ossec/bin/ossec-analysisd root      2050  0.0  0.2  1592  556 ?        S    12:40   0:00 /var/ossec/bin/ossec-logcollector root      2054 12.2  0.3  1756  616 ?        S    12:40   0:05 /var/ossec/bin/ossec-syscheckd

The OSSEC HIDS log file is /var/ossec/logs/ossec.log, so you can check it to see what’s going on, e.g. with the tail command.

tail -f /var/ossec/logs/ossec.log

shows what’s happening in real-time. Press CTRL-C to leave it.

tail -n 100 /var/ossec/logs/ossec.log

shows you the last 100 lines of the OSSEC HIDS log.

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MRTG Installation

Written by Pravin on October 20, 2008 – 5:29 am -

MRTG Installation Gudie:

1)    yum install net-snmp-utils net-snmp, yum install mrtg
2)    service snmpd start
3)    chkconfig –add snmpd
4)    vi /etc/snmp/snmpd.conf
## Find “group   notConfigGroup v2c  notConfigUser” & add ‘rocommunity supp0rt’
Below it & then restart snmpd.
5)    Create a directory ‘mrtg’ or ‘myrtg’ under ‘/var/www/html’ OR
6)    cfgmaker –global ‘WorkDir: /usr/local/apache/htdocs/mymrtg’ –output       /etc/mrtg/mymrtg.cfg supp0rt@ (here the ip will be your server ip.)
7)    vi /etc/mrtg/mymrtg.cfg   & add following.
Target[]: 2:supp0rt@
SetEnv[]: MRTG_INT_IP=”″ MRTG_INT_DESCR=”venet0″
MaxBytes[]: 1250000
Title[]: Traffic Analysis for 2 —

8)    mrtg /etc/mrtg/mymrtg.cfg  (you will get following output)

ERROR: Mrtg will most likely not work properly when the environment
variable LANG is set to UTF-8. Please run mrtg in an environment
where this is not the case. Try the following command to start:

env LANG=C /usr/bin/mrtg /etc/mrtg/mymrtg.cfg

9)    env LANG=C /usr/bin/mrtg /etc/mrtg/mymrtg.cfg  (you will get following output)

10) Point your browser to

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rpm database rebuild

Written by Pravin on October 20, 2008 – 5:21 am -

If any thing does wrong with the RPM database, you can use following way to rebuild the RPM database.

First remove the /var/lib/rpm/__db* files.

root@server [~]# cd /var/lib

root@server [~]# rm __db*

RPM Database rebuild:

root@server [~]# rpm --rebuilddb

root@server [~]# rpmdb_verify Packages

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Written by Pravin on October 20, 2008 – 5:00 am -

LZO – Lempel-Ziv-Oberhumer is a lossless data compression algorithm that is focused on decompression speed. It is a portable lossless data compression library written in ANSI C. It offers pretty fast compression and *very* fast decompression. Decompression requires no memory. In addition there are slower compression levels achieving a quite competitive compression ratio while still decompressing at this very high speed.

Perl-LZO provides LZO bindings for Perl, i.e. you can access the LZO library from your Perl scripts thereby compressing ordinary Perl strings.

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XEN kernel modules

Written by Pravin on October 20, 2008 – 4:33 am -

The Xen kernels are commonly asked for code already in place.

To obtain the already built modules:

To compile your own modules:
tar -xjf xen-source.tbz2
cd linux-2.6.16-xen
gzip -dc /proc/config.gz > .config
make menuconfig
make modules
make modules_install

If you get errors on the make menuconfig stage, be sure to install ncurses-devel.
When selecting modules to compile under make menuconfig, toggle the “M”, not the “Y”.

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Introduction to FileSystem

Written by Mike on September 18, 2008 – 8:54 pm -

Dumping a cupboard-full of documents, audio cassettes, video tapes and even photo albums on a hard drive or DVD might sound easy, but is actually a complex process. Operating systems use logical data structures for storing, organizing and keeping track of files on a partition or on an optical disc, called a Filesystem. The basic function of a FileSystem is to make efficient use of disk space for data storage, ease basic file operations (read, write, copy and delete) and catalogue files for faster retrieval.

A disk partition is like a compartment in a train, while the Filesystem is the seating arrangement fixed within the compartments. Before using any partition on a disk, a logical Filesystem needs to be initialized on it. Let’s have a look at how a typical Filesystem works.

How Filesystems Work?

The space in a hard drive is divided into units called sectors, usually of 512 bytes. The Filesystem groups the sectors together after creating a sector index; the group is called a cluster or an allocation unit. It’s difficult for the Filesystem to deal with data on a sector-by-sector basis, so when the Filesystem needs to access a sector for a read-write operation, it will first define the cluster number of that sector. Then from that cluster, it will use the sector index to access that particular sector. Each logical volume (hard drive) has a table—called the File Allocation Table (FAT)—that carries all the information about the sectors and the files stored on those sectors.

Types of Filesystems

Disk-based Filesystems
These would be found on hard disks, CD-ROMs and DVDs. Files are stored in a sequence of bytes on fixed-sized blocks called sectors; these Filesystems feature random-access file reads and writes, and also file fragmentation across the disk. Some disk-based Filesystems also have journaling and versioning. In a Journaling Filesystem like XFS on the Silicon Graphics platform, changes in files are logged first in a specially allocated area called a Journal before they’re actually written on the main Filesystem. Versioning Filesystems like OpenVMS allow for the existence of several versions of the same file, and take periodic backups. Popular disk-based Filesystems include:

Windows: New Technology File System (NTFS), File Allocation Table (FAT, FAT16, FAT32), and many more;
Linux: ext, ext2, ext2fs, NSS, ReiserFS and several others based on Linux and UNIX variants
Mac OS X: Hierarchical Filesystem (HFS+), HFS, Macintosh Filesystem (MFS), Xsan

Disk-based Filesystems can be further classified into:

Solid-state media Filesystems: These are designed for storing files on devices that rely on Flash memory as their storage. Such Filesystems require special handling, because data blocks wear out if information is repetitively written and rewritten on the drive. Besides, the blocks have to be erased explicitly before any data is written on them. The Journaling Flash Filesystem (JFFS) and Yet Another Flash Filesystem (YAFFS) are popular solid-state Filesystems.

Record-oriented Filesystems: The basic purpose of such Filesystems is to store files in the form of records to be compatible with older operating systems that are used exclusively on mainframes and minicomputers.

Shared-disk Filesystem: These are also known as SAN (Storage Area Network) Filesystems or Cluster Filesystem. As the name suggests, they are used on huge blocks of storage which are directly accessible to computers via a network connection.

Network Filesystems
Network Filesystems (or distributed Filesystems) support the sharing of files, printers and other computing resources over a network. The performance of such Filesystems is measured by the time it requires to satisfy the service requests by different computers connected on the network. Such Filesystems are found on file-servers and provide access to files by acting as clients for remote access protocols like NFS (Network Filesystem) or SMB (Server Message). NFS and SMB are popular examples of network Filesystems. Several network Filesystems prevail today: 9P, Apple Filing Protocol (AFP), NetWare Core Protocol (NCP), Coda, Distributed File System (DFS) and Google File System (GFS), to name a few.

Filesystems are critical for storage media to run properly with the operating system. Regular maintenance and protection from malware is not only advisable, it’s necessary.

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