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Yuri Slobodyanyuk's blog on IT Security and Networking sharing experience and expertise

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Configure DVTI hairpinning on Cisco router for safe browsing

guten Tag everyone, today i am posting the video showing how to configure Dynamic Virtual Tunnel Interface (DVTI) on Cisco IOS router. DVTI for remote access has been available for a long time already and actually comes to gradually replace the old way of dynamic crypto maps, but as always people are hard to get out of the rut so mainly this great feature goes unnoticed.
In this specific setup I am using DVTI for hairpinning – i.e. I will connect using CIsco VPN client to the router and will tunnel ALL of my traffic through this connection, no split tunnel.
The main benefit of DVTI here is that using DVTI interface I can assign it ip nat inside and router will take care of NAT translating my traffic when sending it clear text to the Internet.
Enjoy
As always you can watch all my videos on Vimeo – vimeo.com/yurisk.info, also you can download there videos as files.
Reference on Cisco: DVTI on CIsco.com

Enable RADIUS Authentication for SSH and WEBGui access to the Checkpoint firewall

User actions accountability is one of the building blocks of Non-repudiation in Security.
In Checkpoint , nevertheless, the default (and widely used) user authentication for SSH and WEBGui sessions is local. Actually Checkpoint thought about that long ago and have been offering Radius authentication for users accessing the SecurePlatform via SSH or WEBgui for quite long time. I’ll put the discussion why they did it as a separately priced feature aside.
But if you have SecurePlatform Pro license for NGX R65 or earlier or Advanced Networking Blade for R70 or later then you can use it once Pro features are enabled on the SPLAT.
To help you configuring this I recorded this video , so be secure and enjoy.
PS As always feedback is welcome here as well as to the email yuri@yurisk.info.
Direct link to Vimeo

Encrypting preshared keys stored on the cisco IOS router

You never know where your router may end up . It may be RMA’ed without proper wiping the configuration first, it may be plain simple stolen. In any of these or other unfortunate cases the last thing you would want is for the attacker get passwords or other security information stored on the router.
One piece of such information is preshared key(s) , that by default are stored in clear text.
To address this potential threat Cisco, starting IOS 12.3, provide AES encryption feature on IOS routers to encrypt the stored preshared keys. In video below I recorded you can see the walkthrough to enable and manage this security feature.
Enjoy. As always suggestions, critics, comments are welcome .
NB – Narration is in English.

Cisco – how to schedule an unattended reload with EEM

Good evening everyone,
Today a colleague of mine asked if I had a ready-to-use template to schedule a reload of Cisco IOS router .
–    “Of course, piece of cake, there should be millions of hits on it in Google” , was my thought. So, after 30 minutes of searching the mighty G and being surprised to have found nothing I dragged from my notes this recipe dated 2007 but still valid as ever.
Enjoy.
NB Word of warning to those trying to do it with built in KRON service of IOS – rebooting a router requires to answer  “yes” at the CLI prompt and therefore will NOT work with KRON, only EEM can do it.
IOS used and tested – IOS 12.4T

conf t
Edge(config)#event manager applet ReloadMe
Edge(config-applet)#event timer cron name ReloadMe cron-entry “05 09 * * *”
Edge(config-applet)#action 33 reload
wr mem

This will reload router every day at 09:05, for other formats see man page for cron in Linux

sh run
….
event manager applet ReloadMe
event timer cron name ReloadMe cron-entry “05 09 * * *”
action 33 reload

Enable SNMP v3 in Checkpoint video walkthrough

SNMP version 3 has been with us for so many years but so very few Checkpoint folks use it that I decided to do this screencast/video showing how to enable and use SNMP v3 in Checkpoint firewall. NOTE – the language of narration is Hebrew .

BTW I think of posting more videos like that . All of them will be available under  http://vimeo.com/yurisk

BTW2 If you have free user in Vimeo.com you can download the videos as files as well.

Two tips to secure SSH access from specific IPs to specific users in Checkpoint or any Linux

[showmyads]
Today I’ll bring you two tips to secure SSH access to the Checkpoint firewall beyond firewall rules itself. SSH access is the most powerful way to own the firewall so it should be secured to the paranoid level and even then it is never enough.
Tip 1 Change the listening port.
You may say obscurity is not security but I will not agree – any measure that makes attacking your system harder without much burden on you is valid. After all there is no such thing total security, only endless arms race. Checkpoint just being a Linux in disguise uses OPenSSH server so changing the port is done via :
NOTE before changing listening port don’t forget to allow incoming connection on this port in firewall rules.

/etc/ssh/sshd_config
#Port 22

You change the above line to (if say I want to change port to 5022):

Port 5022

Then save , then restart the SSH daemon:

[Expert@fireball]# service sshd restart

Now you connect to the firewall #ssh -p 5022 user@IP
Tip 2 Limit SSH access per user and per IP address
Openssh provides the possibility to restrict access for specific user to specific IP addresses. I will look here at few potential scenarios.
Case 1 Limit all SSH users to access from specific IP , here from network 99.19.19.0/24:
At the bottom of the same file /etc/ssh/sshd_config I add:

AllowUsers *@99.19.19.*

Save , restart SSH daemon and this will take effect – only users coming from network
99.19.19.0/24 will be able to login by ssh , any other source IP will always get “Wrong username or password”
Case 2 Limit some users to access from specific IPs but allow others from Any.
Checkpoint comes with default user admin that people often do not change, and I concluded over the years that changing people’s bad behavior is much harder than changing firewalls. So I do this:
When both me and client are managing the firewall, i create the username for me , here yurisk and restrict the username admin to internal nets (for emergency cases) and his specific IP.Here my user is yurisk, client’s user is admin and LAN is 10.88.88.0/24 and client’s WAN IP is 123.123.123.10

/etc/ssh/sshd_config
AllowUsers admin@123.123.123.10 admin@10.88.88.* yurisk

How to separate inbound and outbound data graphs in Nfsen Netflow tool

As I said already ( here and here ) for gathering Netflow data, especially with security in mind, I deem Nfsen/nfdump to be the best. And with some easy 2-minutes tweaking I can always make it do exactly what I want.
By default when you configure Cisco to export both ingress and egress Netflow data from the interface Nfdump/Nfsen will accept and process it fine BUT … will show it on the same timeline with the same color and so overlapping over each other. That means you will see only the largest values. To fix it you create additional (from Live) profile with separate Channels, each representing direction of the traffic – inbound or outbound. Then for each channel you set appropriate filter – IN for incoming traffic , OUT for outgoing traffic (all respective to the interface being monitored), followed by SNMP ifIndex of the interface in the router. Picture is worth 1024 words they say , so see below screenshots how I did it for one of my clients.

Nfsen custom profile with channels

Nfsen custom profile with channels


Nfsen custom profile with channels

Nfsen custom profile with channels


[showmyads]

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