Block Skype connections

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There is a popular belief that Skype client is very hard to block on the network layer, due to it’s Peer-To-Peer behavior and usage of HTTP/S ports.

Block Skype client

However at present time (December, 2012) Skype client connections can be blocked pretty simply by a few firewall rules.
After startup, Skype client receives a number of it’s master (login?) servers – dsnX.d.skype.net. Currently there are 16 DNS entries from dsn0.d.skype.net to dsn16.dsn.skype.net.

Using simple bash script (uses Linux DNS utility – dig) we can get most of these server’s IP addresses:

[code]
for i in {0..20} ; do dig +short dsn$i.d.skype.net; done | sort | uniq
[/code]

Just block all access to following networks and Skype client won’t be able to authenticate and connect.

111.221.74.0/24
111.221.77.0/24
157.55.130.0/24
157.55.235.0/24
157.55.56.0/24
157.56.52.0/24
213.199.179.0/24
64.4.23.0/24
65.55.223.0/24

For Linux router, with IPtables firewall, you may use following command:

[code]
for ip in 111.221.74.0/24 111.221.77.0/24 157.55.130.0/24 157.55.235.0/24 157.55.56.0/24 157.56.52.0/24 213.199.179.0/24 64.4.23.0/24 65.55.223.0/24; do iptables -A OUTPUT -d $ip -j DROP; done
[/code]

Tags: Posted by BackTrack in Linux, Networking on December 29, 2012
20 Replies

Search recursively in file contents

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There is a very useful command to search for a particular string in file in bash. It will search subdirectories as well and display a full path to the file, containing the string.
[code]
find . -type f -exec grep -Hn “emacs” {} \; 2>/dev/null
[/code]
Output:
./anaconda-ks.cfg:56:emacs
./install.log:282:Installing emacs-leim-21.4-24.el5.x86_64
./install.log:592:Installing emacs-common-21.4-24.el5.x86_64
./install.log:781:Installing emacs-21.4-24.el5.x86_64
./install.log:792:Installing emacspeak-23.0-3.el5.noarch

The 2>/dev/null argument will hide annoying errors like grep: line too long.
If you want to limit the depth of subdirectories, use -maxdepth X argument. Where X is >0.

For a search in current directory, grep alone is sufficient:

[code]
grep -Hn “string” *
[/code]

Tags: , Posted by BackTrack in Linux on December 25, 2012

Zabbix 2 CheckPoint SNMP template

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I have created Zabbix 2.x Template for monitoring CheckPoint products via SNMP.
This template utilizes custom CheckPoint MIBs that are located on SecurePlatform OS in $CPDIR/lib/snmp/

You can also download CHECKPOINT-MIB file here (from R75 version):
http://pingtool.org/downloads/CHECKPOINT-MIB.txt

You need to copy this file to your Zabbix server, into directory /usr/share/snmp/mibs
To test new MIBs, run a snmpget command as follows:

SNMPv2: [code]snmpget -v2c -c -Of CHECKPOINT-MIB::svnVersion.0[/code]
SNMPv3: [code]snmpget -v3 -l authpriv -u -A -X -Of 192.168.14.3 CHECKPOINT-MIB::svnVersion.0[/code]

This command should return the product version:
.iso.org.dod.internet.private.enterprises.checkpoint.products.svn.svnInfo.svnVersion.0 = STRING: “R75.40”

Download links for Templates:

SNMPv2: http://pingtool.org/downloads/zbx_CheckPoint_SNMP.xml
SNMPv3: http://pingtool.org/downloads/zbx_CheckPoint_SNMPv3.xml

SNMPv2 template will try to link standard Zabbix’s Templates:”Template SNMP Device and Template SNMP Disks.

SNMPv3 template will try to link my own SNMPv3 Zabbix Templates: Template SNMPv3 Device and Template SNMPv3 Disks.

You can get these SNMPv3 templates from here

Tags: , , , Posted by BackTrack in Linux on December 19, 2012
5 Replies

Zabbix 2 SNMPv3 device template

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Zabbix comes with predefined SNMP Device Template, that is configured to access devices with SNMP version 2.
Here is modified version of 3 Zabbix’s templates for use with SNMPv3.

Zabbix SNMP v3 Template

It will add 7 new templates:

Template SNMPv3 Device
Template SNMPv3 Generic
Template SNMPv3 Interfaces
Template SNMPv3 Disks
Template SNMPv3 Processors
Template SNMPv3 OS Linux
Template SNMPv3 OS Windows

Download: zbx_SNMPv3_template.xml

To add this new template to your Zabbix, press “Import” button on templates page and select the xml file.

Template uses following macroses:

{$SNMP_SECNAME} – SNMPv3 username
{$SNMP_AUTH} – authentication password
{$SNMP_PRIV} – encryption passphrase

These macros have to be defined on hosts page:

Configuration – Hosts – <host using SNMP v3> – Macros – Add

Tags: Posted by BackTrack in Linux on October 31, 2012
6 Replies