Sunday, August 19, 2007

Quest VAS Test (Vintela Authentication Services)

I've done a quick test Quest VAS (Vintela Authentication Services) as an implementation for Unix/Linux Authentication with Active Directory.

First impression is that this is a very nice tool that will make your life easier if you wish to implement authentication from different *nix like OS's with AD.

The installation is very easy. All we need to do is install the server side (2min) and than the client side (1 RPM for Authentication and 1 for Group Policy (if needed)).

What we have done is:
  • Install the server side on your domain controller
    • Create users and groups for use in *nix machines
  • On the Linux/Solaris machine:
    • Install the rpm/pkg
    • Check if the server can find the domain controller LDAP service by running:
      dig SRV _ldap._tcp.
      For example, if my domain name is uxdc.corp then run:
      dig SRV _ldap._tcp.uxdc.corp
    • Synchronize the server time from the domain controller:
      /opt/quest/bin/vastool timesync -d
    • Restart VAS daemon:
      /etc/init.d/vasd restart
    • Restart Group Policy daemon:
      /etc/init.d/vasgpd restart
    • Join the server to the domain:
      /opt/quest/bin/vastool -u administrator join -f
For my opinion the advantages of VAS over the configuration of nss, ldap and pam are:
  • Easy to install and configure
  • Encrypted ldap using Kerberos
  • Same installation and configuration process for all *nix like OS's
  • Automatically generates the server keytab after joining the server to the domain
  • Allow users password change from Unix
  • Timesync solution included without the need to use ntp
  • Manipulating AD objects from the Unix command line
  • Server based user access control
  • Personality Management, the ability of users to impersonate to different personality
  • Central place for configuring sudo/profile (Management from AD)
  • Supports better encryption type - arcfour-hmac-md5
  • File distribution and file permissions capability from AD
  • The ability to create services keytabs from the Unix CLI
Quest VAS site

Wednesday, August 15, 2007

Fair Scheduler support for Linux

Just few days ago I wrote about my experience with Solaris FSS and now I found out that Linux kernel 2.6.24 will support CFS (Completely Fair Scheduler). This should be very interesting to test...

Actually CFS is merged in release 2.6.23 but depends on some unmerged containers, so we will have to wait for release 2.6.24..

Can't wait to test it.


See Who's Editing Wikipedia - Diebold, the CIA, a Campaign

"Wikipedia Scanner -- the brainchild of Cal Tech computation and neural-systems graduate student Virgil Griffith -- offers users a searchable database that ties millions of anonymous Wikipedia edits to organizations where those edits apparently originated, by cross-referencing the edits with data on who owns the associated block of internet IP addresses."

Read more here.

Tuesday, August 14, 2007

YAST for Redhat

Oracle migrated YAST to work with RHEL/Centos/Oracle Enterprise Linux (all the same)...
The download is available here.

Monday, August 13, 2007

Oracle new filesystem??

I've just found out that Oracle is developing a new file system for Linux, I really don't understand what they are doing...

They started with OCFS, than OCFS2 (every thing is OK till now), than ASM and telling every one that this is the best choice for them and not OCFS/OCFS2, and now BTRFS (Btree File System).

What next?


Solaris 10 - Resource Management

Today we've started testing Solaris 10 CPU resource management using FSS (Fair Share Scheduler) and Projects.

The problem we wanted to solve is with Oracle database, we have a DWH database and at night we have few things:
  • ETL
  • Database Exports
  • Users access
What we need is that the database exports won't interrupt the ETL process (The users don't do much at night), So we've decided to try Solaris Resource Management capability.

Before I'll show what we have done you need to know that the Oracle owner is "orauser"
and the Oracle SID is "orcl".

The first step is to create the needed projects, projects are used to distinguish different workloads from one another. We've created two projects:
  • user.orauser
  • oracle_low
There are three ways to create a project:
  1. user.USERNAME - a project that is associated with a specific Unix user
  2. group.GROUPNAME - a project that is associated with a specific Unix group
  3. project name - a project that is not associated to any group or user by default and can be associated manually or by SMF (Service Management Facility)
So the first project we've created, user.orauser, will be assigned automatically for the user orauser. The second project, oracle_low, is a non associated project that we will use to lower the CPU workload for the database exports.

The commands to create a the projects are:
# projadd -c "Oracle default project" user.orauser
# projadd -c "Oracle low priority project" oracle_low

All the projects defined in /etc/projects file and can be viewed in this file or by running:
# projects -l

To check orauser default project run:
# id -p orauser
uid=60000(orauser) gid=300(dba) projid=100(user.orauser)

Now that we've created the projects, we need to change the system scheduling to use FSS:
# ps -cafe
# dispadmin -d FSS
# priocntl -s -c FSS -i class TS
# priocntl -s -c FSS -i pid 1
# ps -cafe

  • "ps -cafe" - shows all processes and there scheduler class, I will not explain what a class is, but you should know that TS class is what Solaris uses for all processes by default. The TS class can be manipulated by the nice and renice commands.
  • "dispadmin -d FSS" - sets the default scheduling class to be used on reboot to FSS
  • "priocntl -s -c FSS -i class TS" - changes all current process with TS class to FSS class
  • "priocntl -s -c FSS -i pid 1" - changes the /sbin/init process to FSS class
The next step is to add the CPU resource (cpu-shares) to each project, one thing we need to know about cpu-shares resource is that the value we set for it is the ratio and not percentages, it means that if project A have cpu-shares=10 and project B have cpu-shares=20 and both process of both projects need 100% CPU load the processes of project B will get total of 66% CPU and the processes of project A will get 33%. So, here is the way to add the CPU resource to our projects:
# prctl -n project.cpu-shares -r -v 30 -i project user.orauser
# prctl -n project.cpu-shares -r -v 10 -i project oracle_low
# projmod -sK “project.cpu-shares=(privileged,10,none)” oracle_low
# projmod -sK “project.cpu-shares=(privileged,30,none)” user.orauser

  • projmod - changes the project attributes
  • prctl - changes the resource control for running process
Use the "projects -l" command to view the changes we've just made.
# project -l user.orauser
# project -l oracle_low

Now, we changed the export processes to run like this:
# newtask -p oracle_low /u01/scripts/

And every thing is working perfectly!!! Fun Fun Joy Joy.

One more useful command is "prstat -J" that will show resources utilization by project.


Thursday, August 09, 2007

ksvalidator - validate kickstart file syntax

Finally, in Redhat 5 there is a tool called ksvalidator and we can use it to validate the syntax of a kickstart file!!

ksvalidator comes with the system-config-kickstart RPM and can be used this way:
system-config-kickstart mykickstartfile.ks


How to secure your new linux installation

I've decided to publish my Linux Security document. You can download it from here as a pdf version.

1. Introduction

This document is intended for linux administrator and security personal. The purpose of this document is to secure linux servers for production use. This document shows how to secure a default installation of Redhat Enterprise Linux but can be adopt for other linux distors as well.

2. Installation process

· The Redhat server "Install Everything" installation, installs more than 1000 RPM's in RHEL5 and more than 1400 RPM's in RHEL4. The best way to install a server is to "Install what you need", Use the "Minimum" installation and after the install add what you need or to use the "Custom" installation and select the packages needed. (NOTE: The minimum installation installs less than 300 packages!)

· Patch the servers to the latest patch available - After the installation, the server should be patched to the latest errata available. Run "up2date –u" to update the system, If there is no internet connection then download the latest patch from Redhat web site.

· Some packages are not recommended for installation on a server:

o X/Gnome/KDE – The reasons to not install X/Gnome/KDE are performance and security issues

o Telnet/Ftp/Rsh – SSH is much better solution to for all those tools

· If the OS is already installed then remove unnecessary software

· Partition your disks to:

o / - 2G

o /var – 1G (can be smaller)

o /var/log – 1G

o /tmp – 2G

o /usr – 4G (this is the main directory used for tools)

o /usr/local – 1G (can be smaller)

o /home – 500M (depends on the space needed by users)

o /opt – 500M

o /boot – 100M

3. Run level

The linux machine run level is used to define what system services are operating. There are seven run levels:

· 0: Halt the machine

· 1: Single user mode

· 2-5: Normal operating mode (user defined)

o 2 – Multiuser, without NFS

o 3 – Full multiuser mode

o 4 – Unused

o 5 – X

· 6: Reboot

The default run level for a server should be 3. Run level 3 will start without X (GNOME/KDE/other).
To change the default run level on boot you should edit the file /etc/inittab and change the default run level by editing this line:



4. Detect open ports

One of the most important things is to close all unneeded network ports and know which ports you leave open. To get the list of open ports run:

netstat –tulpn

The output of this command will return something like this:

Active Internet connections (only servers)

Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name

tcp 0 0* LISTEN 2391/portmap

tcp 0 0* LISTEN 1966/sshd

udp 0 0* 1570/dhclient

udp 0 0* 2391/portmap

Services/ports that you may not want to leave running/open are:




Handle service



SMTP protocol

If you need the server to act as SMTP server for outgoing emails only then go to "Secure Sendmail" Section in this document. If you don't need to use this server as SMTP server in any way you can stop it by running:
service sendmail stop

chkconfig sendmail off

Portmap (RPC)


Handles RPC calls
Used by NFS client

service portmap stop

chkconfig portmap off


UDP:32768, 729

Used by NFS client

service nfslock stop

chkconfig nfslock off



Printing service

service cups stop

chkconfig cups off



HP Linux Imaging and Printing

service hplip stop

chkconfig hplip off


UDP: 1024, 5353, 1025

Multicast DNS service Discovery

service avahi-daemon stop

chkconfig avahi-daemon off

5. Stop unneeded services

The default installation starts some services that you may not need or wish to leave running, this list will show most of them. First of all, the way to get the list of running services is:

chkcnfig –list | grep ":on"

The output for this command will return something like this:

acpid 0:off 1:off 2:off 3:on 4:on 5:on 6:off

anacron 0:off 1:off 2:on 3:on 4:on 5:on 6:off

apmd 0:off 1:off 2:on 3:on 4:on 5:on 6:off

atd 0:off 1:off 2:off 3:on 4:on 5:on 6:off

auditd 0:off 1:off 2:on 3:on 4:on 5:on 6:off

autofs 0:off 1:off 2:off 3:on 4:on 5:on 6:off

avahi-daemon 0:off 1:off 2:off 3:off 4:off 5:off 6:off

avahi-dnsconfd 0:off 1:off 2:off 3:off 4:off 5:off 6:off

bluetooth 0:off 1:off 2:on 3:on 4:on 5:on 6:off

conman 0:off 1:off 2:off 3:off 4:off 5:off 6:off

cpuspeed 0:off 1:on 2:on 3:on 4:on 5:on 6:off

crond 0:off 1:off 2:on 3:on 4:on 5:on 6:off

firstboot 0:off 1:off 2:off 3:on 4:off 5:on 6:off

gpm 0:off 1:off 2:on 3:on 4:on 5:on 6:off

To stop a service from running and start at boot time use:

service stop
chkconfig off

List of services that run by default:

Service name




Handles ACPI event and invokes the command. For example, what happens when the power/sleep button is pressed or AC adapter state is changed.



Like cron but it will run jobs that didn't run because the server was down.



Monitoring battery status



Automates a packet filtering firewall with arptables



The same tool as cron. Needed only if using the at command.



Handles the audit system



Automount filesystems

If using autofs


MDNS/DNS-SD, Multicast DNS service Discovery

If using MDNS


Daemon which configures unicast DNS servers using server info published via mDNS

If using MDNS


Bluetooth services for service discovery, authentication, Human Interface Devices, etc

If using Bluetooth devices


Japanese Conversion Engine



Monitors the systems idle percentage and reduces or raises the CPUs clock speeds and voltages accordingly to minimize power consumption

claims it can be off


Handles corn jobs



configuring printers through D-BUS



Run the first boot program if this is the first boot or run the reconfiguration program if reconfiguration file exists



Mouse support for text based mode



Daemon for collecting and maintaining information about hardware from several sources.



Bluetooth Human Interface Device Daemon. Provides keyboard, mouse etc. functionality over Bluetooth.

If using Bluetooth


HP OfficeJet Linux driver



Needed if using IM



Iptables firewall for IPv6



Iptables firewall for IPv4



The irqbalance daemon will distribute interrupts across cpus on a multiprocessor/multithreaded system with the purpose of spreading the load. Can be disabled on a single CPU machines.






Discover new hardware (can run manually). Run it manually in case of hardware changes.



Monitoring motherboard sensor values

Why not


SELinux Context Translation System Daemon

If using SELinux


Software RAID monitor

If using software RAID


This is a daemon which broadcasts notifications of system events and other messages.



Apply cpu microcode (IA32 Arch)



Mount network filesystems on boot. This service is needed when using NFS filesystems.



Network configuration



Activates/Deactivates InfiniBand Subnet Manager

If using InfiniBand


Handles pcmcia devices



Smart Card support



If using rawdevices

If using rawdevices


Prereads programs required for startup into memory

Why not?


Prereads programs required for startup into memory (/etc/readahead.d/*.early)

Why not?


Prereads programs required for startup into memory (/etc/readahead.d/*.later)

Why not?


Used when using SELinux to restore specific files security context

If using SELinux


Redhat network daemon

If using RHN updates


manages RPCSEC GSS contexts for the NFSv4 client

If using NFSv4


maps user names to UID and GID numbers for NFSv4

If using NFSv4


starts the SELinux Troubleshooting Daemon

If using SELinux


Self Monitoring and Reporting Technology (SMART) Daemon






Starts syslog



X font server. You can load it only in run level 5.



Xinetd service



Provides notification of updates which are available to be applied to your system

If using network updates using yum

To check which xinetd services run by default:

chkconfig --list | awk '/xinetd based services/,/""/' | grep on

Service name




allows remote daemons to query information about users establishing TCP connections on the local server


6. Remove unneeded LKM's (Loadable Kernel Modules)

Loadable kernel modules will be loaded when they are needed by the OS/tools, so after disabling all unneeded services we can see that the amount of loaded modules (using lsmod) before is much greater than now.

To disable unneeded LKM's we can use this method:

· lsmod – Displays a list of all loaded modules

· modinfo - Displays information about a specific module

· rmmod – Will try to unload a module (if not used)

To prevent a specific LKM from loading at boot time you will need to change the modprobe configuration files:

· RHEL4 – edit /etc/modprobe.conf and add the line:
alias off
for example: "alias floppy off"

· RHEL5 – edit /etc/modprobe.d/blacklist and add the line:

To find the you can use modinfo and get the value in the alias field for example: "modinfo ipv6".

7. Disable CTRL+ALT+DEL

CTRL+ALT+DEL are the default keys defined to reboot the machine, we've seen few cases which cause this defaults to reboot a production server because of a human mistake. To remove this default, edit the file /etc/inittab and comment the line:

ca::ctrlaltdel:/sbin/shutdown -t3 -r now

Or to this line if you whish to echo a message when buttons are pressed:

ca::ctrlaltdel:/bin/echo "CTRL+ALT+DEL is disabled."

after saving the file run this command to reload the init settings:

init q

8. Disabling IPv6

To disable IPv6 you need to:

· Add this line to /etc/modprobe.conf:
alias net-pf-10 off

NOTE: if the line "alias net-pf-10 ipv6" exists in the file, change it.

· Add this line to /etc/sysconfig/network

NOTE: If the line "NETWORKING_IPV6=yes" exists in the file, change it.

9. Secure SSHD

SSH is the replacement for telnet, rsh, rcp and rlogin, with SSH you can create an encrypted & secure connection to the machine. The main sshd configuration file is /etc/ssh/sshd_config.

· To restrict direct root login via ssh set:
PermitRootLogin no

· Allow only ssh version 2 connections, set:
Protocol 2

· Ensure that strict mode is enabled to check file permissions and ownerships of important files locate at the user home directory. With this setting set to yes the sshd will fail connection to the user if the files are not set correctly:
StrictMode yes

· Disable all host based authentications via ssh:
IgnoreRhosts yes

HostbasedAuthentication no

RhostsRSAAuthentication no

· Set idle session timeout to 15 min:
ClientAliveInterval 300
ClientAliveCountMax 3

· Allow only specific users to connect via ssh by create a sshgroup and enable it in ssh:
AllowGroups sshgroup

· Disable sftp if not needed, remark the line:
Subsystem sftp /usr/lib/misc/sftp-server

· Use privilege separation to separate the ssh daemon into two parts, a small part will run as root and the second part will run in cohort jail environment. To do this set:
UsePrivilegeSeparation yes

10. Kernel Security Tuning




TCP SYN attack cookie protection

TCP SYN Attack is a DOS attack that consumes all the resources of a machine.

net.ipv4.tcp_syncookies = 1

Disable IP forwarding

Disable ip forwarding. This parameter should be set to 1 when the linux server acts as a router.

net.ipv4.ip_forward = 0

Disable IP source routing

Source routing is used to specify a path or route through the network from source to destination. This feature can be used by intruders to send a new source route to route traffic to different place and listen to the server network without the server know it happens.

net.ipv4.conf.all.accept_source_route = 0

Disable ICMP Redirect Acceptance

ICMP redirects are used to tell a server the better path to other networks than the one chosen by the server. This feature can be used by intruders.

net.ipv4.conf.all.accept_redirects = 0

Enable IP Spoofing Protection

IP sppofing is when an intruder change the source of an IP packet.

net.ipv4.conf.all.rp_filter = 1

Disable ping

Disable ping requests

net.ipv4.icmp_echo_ignore_all = 1

Disable broadcast requests

Disable broadcast requests

net.ipv4.icmp_echo_ignore_broadcasts = 1

Alert for bad error messages in network

net.ipv4.icmp_ignore_bogus_error_responses = 1

Enable logging

Enable logging of source route packets, spoofed packets and redirect packets

net.ipv4.conf.all.log_martians = 1

11. Lock unused accounts

There are many accounts created with linux installation (more than 40), most of them are locked already locked. We will check the users that are not locked and decide what to do with each account.

To get the list of open account use:

cat /etc/passwd | grep -v nologin | grep -v false | grep -v root | grep -v sync | grep -v shutdown | grep -v halt





Used when using the machine as a news feed server



Used for postgresql database



Used for mysql database



Send oops data and memory dumps over the network



Parallel processing, used for GRID



IMAP server



Backup tool


12. Configure TCP-Wrapper

To allow access from and to specific networks/servers/services we can use TCPWrapper.

The configuration files for TCP Wrapper are:

§ /etc/hosts.allow

§ /etc/hosts.deny

The files format is:

: [ : shell command ]

Useful man pages for more information:

§ hosts_options(5)

§ hosts_access(5)

NOTE: hosts.allow file take precedence over hosts.deny.

For example:

§ Allowing access via ssh only from specific hosts/subnets:
sshd: server1 server2

§ Allowing any type of access to the server only from specific hosts/subnets:
ALL: server1 server2

§ To remote logging all connections from server1 use:
sshd: server1: spawn echo "Login from %c to %s" | mail –s "Login"

NOTE: For more complex filtering we can use iptables.

13. Password policies

13.1. Password Aging

· Edit /etc/login.defs


· Edit /etc/default/useradd

o Change the value of: EXPIRE to the number of days the password will live

o Change the value of: INACTIVE to the number of days that the user will be locked after a password expires

o Or use chage…

· use passwd –S to get password aging information for a user

13.2. Strong password enforcement

· Edit /etc/pam.d/system-auth and add:
minlen=10 lcredit=-1 ucredit=-1 dcredit=-1 ocredit=-1 difok=3
To the end of the line:
/lib/security/$ISA/ retry=3

13.3. Password history

· Edit /etc/pam.d/system-auth and add:
To the end of the line:
/lib/security/$ISA/ nullok use_authtok md5 shadow

13.4. Locking user after too many logins

· Edit /etc/pam.d/system-auth and add:
auth required /lib/security/$ISA/ onerr=fail no_magic_root
after the line:
auth required /lib/security/$ISA/
Also, add the line:
account required /lib/security/$ISA/ per_user deny=5 no_magic_root reset
after the line:
account required /lib/security/$ISA/

14. Set accounts ulimits

To prevent accidental DOS we will set ulimits for all users/groups that we use. This example will show how to set the ulimit for oracle user and for users group. We will use only 2 type of limits (nofile and nproc), but there are more than 10 other types of limits that can be set, like memory, cpu, max logins and more.

· Edit /etc/security/limits.conf, and add:

o For oracle account:
oracle soft nofile 4096

oracle hard nofile 63536
oracle soft nproc 2047
oracle hard nproc 16384

o For the users group:
@users soft nofile 500
@users hard nofile 1000
@users soft nproc 250
@users hard nproc 500

15. Enable auditing

Auditing will log all activities made by users, the drawback of linux auditing system is that we are unable to see the parameters used by a command, for example, if a user will run the command "rm –rf" we will only see rm in the audit trail.

Auditing users commands is available by psacct daemon.

To enable psacct run:

/etc/init.d/psacct start

chkconfig psacct on

Commands to get information from psacct database are:

§ lastcomm – last commands by users

§ ac – statistics about users connect time

§ ac –p – Total time for each user

§ ac –d – Total time for each day

§ sa – summarize accounting information

§ sa –u – print the user for each command

§ sa –m – CPU usage per user

§ and more options for each command (sa, ac, lastcomm)…

16. Patch management

There are few patch management solutions, here is a list of a few products:

· Yum (Yellow dog Updater, Modified) – Opensource tool to manage RPM based installations

o Opensource & Free

o Simple to use and manage

o No central management console

· Redhat default up2date solution:

o No central management console

o Each server handles it's own updates

o Each server need access to RHN (can be solved by http proxy server)

· Redhat Satellite server –Implements a solution for patch management by creating a single server that all servers register to get the new patches. This server collects all needed information and packages from Redhat Network for all the registered servers, and can automatically/manually update the registered servers. The satellite server is the only one that needs to have access to the Internet. Redhat Satellite server benefits:

o Single place to manage all servers

o Single place with access to the internet. Can be protected by firewalls.

o Monitoring system – can monitor servers performance

o Network based server install (Kickstart install solution implemented)

o Servers cloning (clones software that were installed by RPM's only)

· IBM Tivoli provisioning management

· HP Radia

· Quest configuration management for SMS

17. Enable iptables

Using iptables we can filter/reroute/logging packets and more. For example, if we would like to allow connections log all packets received from a specific ip on a specific port we can do it with iptables.
I will not discuss iptables in this document, but this is a very good way to do this type of jobs.

iptables can be loaded by the services:

§ iptables6 – for IPv6

§ iptables – for IPv4

If you will use iptables to forward communication you will also need to set the kernel parameter ip_forward to 1.

18. Syslog shipping (Remote Logging)

Syslog can send the log records to a remote host for central monitoring, protecting the data from the administrator and from hackers. To do this all you need to do is:

§ On the syslog server side (The server that will log and save the data) edit the file /etc/sysconfig/syslog and add "-r" to the SYSLOGD_OPTIONS variable and restart syslog daemon.

§ On each client add the following line to /etc/syslog.conf and restart the syslog daemon:
*.* @syslog-server
Where syslog-server is the syslog server name/ip.

NOTE: Running syslog server (The server that will log and save the data) will open UDP:514 port.

19. Apache Hardening

Apache is the default web server for linux and the most common web server on the internet. Because of this, apache is a very secure web server but there are few things to do when configuring apache, the main configuration file of apache is /etc/httpd/conf/http.conf:

§ By default apache bounds it self to all networks (Ethernet interfaces) available in the server. Bounding apache to listen to specific interface will minimize the vulnerable of apache, to do that we will need to set the parameter: Listen to smoothing like this:
Where is the ip address that we wish apache to listen on.

§ The default configuration of apache is to follow symbolic links and this could be exploited by hackers, to disable this feature remove the "FollowSymLinks" option from apache configuration file.

§ Remove SSI (Server-Side Includes) support – SSI is a way to run server side commands before an html is delivered to the client. SSI is usually disabled by default, to check that that it is also true for our installation check if the option "+Includes" exists in apache configuration files.

§ Disable CGI support – apache CGI support is a way to run scripts from apache, this could be exploited if the script is not written in a secure way. CGI is enabled for all "ScriptAlias" directories and disabled for all other directories by default. To check that the CGI is disable in our installation we need to check that the "ExecCGI" option is not used.

§ Remove unused modules – apache comes with a very big set of loadable modules, we can find the loaded modules in apache configuration files by looking for the directive "LoadModule". It is a good idea to comment the modules that are not used. Here is a list of few modules that are not used commonly, and can be removed probably:

Module Name



LDAP support


LDAP authentication with apache


SSI support


WebDAV support


Needed if using the Index option


Provides a comprehensive overview of the server configuration


Provides information on server activity and performance


filesystem provider for mod_dav


HTTP proxy server


FTP support module


HTTP support module


Execution of CGI scripts

§ Hiding apache version number and other sensitive information by setting:
ServerSignature Off

ServerTokens Prod

§ Turn off support for .htaccess files, This is done in a Directory tag with the AllowOverride directive. Set it to None:
AllowOverride None

§ Lower the "Timeout" value to 45

§ Limiting large requests:

o Limiting the size of a body requests to 1MB (Do not set this if allowing to upload large files):
LimitRequestBody 1048576

o Limiting the size of an XML file (if using webdav):
LimitXMLRequestBody 10485760

o You can also check "LimitRequestFields", "LimitRequestFieldSize" and "LimitRequestLine". These directives are set to a reasonable defaults for most servers, but you may want to tweak them to best fit your needs.

o Use SSL communication, apache support SSL and can be very easily configured for ssl.

o The final thing to do, but only if truly needed is to run apache in a chrooted environment. This is very tricky thing to do, but possible, we will not discuss this in here.

20. Sendmail Hardening

Sendmail is the default mail server for linux, it's not very secure and pretty hard to configure, But Sendmail is usually used for local mail delivery and not as an SMTP server, if you need an SMTP server I recommend postfix over Sendmail. To use Sendmail for local mail delivery we don't need it to listen to SMTP port 25, to do that all we need to do is edit the file /etc/sysconfig/Sendmail and change the DAEMON variable from "yes" to "no" like this:

21. NFS Hardening

§ Use NFS over TCP

§ Restrict use for NFSv3 and v4 only

§ Use TCP wrapper on NFS

§ Export only to those machines that you really need

§ Use fully qualified domain names

§ Export only directories you need to export

§ Export read-only wherever possible

22. Antivirus

Antivirus for linux are no commonly used unless:

· The server role is a windows file server using samba

· The server role is a mailserver

There are three very well known anti-viruses for linux:

· ClamAV – OpenSource antivirus

· Panda – Commercial antivirus

· McAfee LinuxShield - Commercial antivirus

23. Other tools worth checking

23.1. Nessus

Nessus is a very popular vulnerability scanner used, started as an opensource and now it's a closed source but still available for free download.

23.2. Bastille Linux

Bastille Linux is a tool that helps protecting the operating system by setting a large amount of parameters. It's a good thing to run this tool after implementing this document.

23.3. DenyHosts

DenyHosts is a script intended to be run by Linux system administrators to help thwart SSH server attacks (also known as dictionary based attacks and brute force attacks)

23.4. Checking for rootkits

Rootkits - (Wikipedia) a set of software tools intended to conceal running processes, files or system data from the operating system. Rootkits have their origin in benign applications, but in recent years have been used increasingly by malware to help intruders maintain access to systems while avoiding detection. chkrootkit is one of the most commonly used for rookits checking.

23.5. Nikto

Nikto is an Open Source web server scanner which performs comprehensive tests against web servers.

23.6. Tripwire

Tripwire is a file and directory integrity checker. Tripwire is a tool that aids system administrators and users in monitoring a designated set of files for any changes.

23.7. Ntop

ntop is a network traffic probe that shows the network usage, similar to what the popular top Unix command does.