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Category Archives for "Brezular’s Blog"

Cracking WPA/WPA2 Pre-shared Key Using GPU

The WPA/WPA2 4-way authentication handshake between AP (authenticator) and client (supplicant) is used to generate encryption keys. These keys are then used to encrypt data sent over wireless medium. In the previous tutorial, we installed the aircrack-ng suite to capture and crack the 4-way authentication handshake to obtain passphrase needed to access a wireless network. […]
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VyControl Installation on Standalone VyOS Router

So far, we have discussed both the manual and Docker methods of installing VyControl. The manual method consists of cloning the VyOS git repository and installing Python dependencies in a virtual environment. The Docker method is based on downloding VyControl Docker image from Docker hub and launching the container. In both cases, VyOS controller is […]
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VyControl – Web UI for VyOS Firewall

VyControl project is a single frontend interface to manage a single or multiple VyoS servers. It was developed by Roberto Berto and is written in Django/Python. It currently supports firewall and static routes configuration. Additional features are planned such as IPSEC, openvpn and basic dynamic routing. My goal is to provide easy-to-reproduce installation steps so […]
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Docker Installation on VyOS

Docker really makes it easier to create, deploy, and run applications by using containers, and containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and ship it all out as one package [1]. I would like to share the script vyos-docker-install.sh, which […]
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Cracking WPA/WPA2 Pre-shared Key

This tutorial illustrates cracking of pre-shared key which is needed to gain an access to a WPA/WPA2 network. Instead of explaining the theory behind the attack, I focus on providing commands that you can easily copy and paste and penetrate the network. However, I strongly recommend getting a background to this topic by studying online […]
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Playing with Python Ransomware

I recently came across the Python script pokus.py which implements a ransomware function. The code is written for demonstration purposes only, so it completely lacks obfuscation techniques. The goal is to identify the vulnerability that is intentionally implemented in the code so we can restore the attached file - private.gif.rsw (the file is compressed by […]
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Remotely Triggered Black Hole Filtering as Service

Remotely triggered black hole (RTBH) filtering is a technique that provides the ability to drop undesirable traffic before it enters a protected network. It is commonly used for the mitigation of distributed-denial-of-service (DDoS) and DoS attacks. We have covered a configuration of source and destination RTBH for Cisco IOS-XR in a previous tutorial. A trigger […]
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Remotely Triggered Black Hole Filtering

Remotely triggered black hole (RTBH) filtering is a technique that provides the ability to drop undesirable traffic before it enters a protected network. It is used for the mitigation of distributed-denial-of-service (DDoS) and DoS attacks. We will show configuration of destination and source RTBH for Cisco IOS-XR in a network depicted on the Picture 1. […]
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BGP FlowSpec on Arista vEOS

BGP FlowSpec is an another Multiptocol-BGP extension with SAFI 133. Created for the purpose of DoS and DDoS attacks mitigation, it brings a new NLRI that collects 12 types of L3 and L4 information. These information creates a flow which defines criteria used for matching DDoS parameters. For instance, a flow can match victim's IP, […]
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LXC as Virtual Service Container on IOS XE

In the last tutorial, we have discussed Cisco open service container based on Kernel Virtual Machine (KVM). Virtual machines include the application, binaries and libraries along with entire guest OS. As a result, we can run any guest OS supported by KVM hypervisor. Containers, however share the same kernel with; each container still acts as […]
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Hosting KVM Apps Inside IOS XE Virtual Service Container

Service Containers are applications that can be hosted directly on Cisco IOS XE routing platforms. Service containers are either Linux Virtual Containers (LXC) or Kernel Virtual Machine( KVM) based virtual machines. A typical Cisco service container carries a digital signature that verifies it as an authentic application from Cisco. An open service (unsigned) container is […]
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Urban Terror Server on Cisco CSR1000v

We have discussed the configuration of Guest Shell on Cisco CSR 1000v platform in a previous tutorial. The guest shell is a built-in Linux container with CentOS 7 installed, which can be activated on the fly when Linux applications are needed. Our lives are currently affected by SARS-CoV-2 and long-standing quarantine, so why not do […]
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Legacy Open Switch 0.4.0 Image

The Open Switch 0.4.0 is the legacy Open Switch version with Cisco like CLI that I used to use in my tutorials. As it can be downloaded anymore, I share the VMDK image below. Please, use the image for learning or demonstration purpose only because this Open Switch version is discontinued. Instead, use the Open Switch […]
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Guest Shell Built-in Linux Container on Cisco IOS-XE

IOx (IOs + linuX) is Cisco's Application Hosting Infrastructure for Cisco IOS XE devices (e.g. CSR1000v). IOx enables hosting of applications and services developed by Cisco and third-party developers in network edge devices across diverse hardware platforms. The Guest Shell is a built-in Linux container (LXC) with a CentOS 7 running on Cisco IOS-XE platforms […]
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Virtual eXtensible LANs -VXLANs

The tutorial discusses configuration of VXLANs on Arista vEOS and Openvswitch virtual machines. The VXLANs extend an L2 network by connecting VLANs from multiple hosts through UDP tunnels called VXLAN segments. VXLANs use Internet Protocol (both unicast and multicast) as the transport medium. VXLAN segments are identified by a 24-bit Virtual Network Identifier (VNI). Within […]
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Virtual eXtensible LANs – VXLANs

The tutorial discusses configuration of VXLANs on Arista vEOS and Openvswitch virtual machines. The VXLANs extend an L2 network by connecting VLANs from multiple hosts through UDP tunnels called VXLAN segments. VXLANs use Internet Protocol (both unicast and multicast) as the transport medium. VXLAN segments are identified by a 24-bit Virtual Network Identifier (VNI). Within […]
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Cloning Remote Linux Machines

I would like to share the second version (1.1) of the Bash script backup_images-1.1.sh which you can use for cloning disks of remote Linux machines. The script reads IP addresses of the hosts from a file and copy the disks with dd command over SSH connection. The disks are stored on a local machine, compressed […]
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Use TheGreenBow VPN Client to Connect with VyOS

The site-to-site Virtual Private Networks (VPN) connect two or more remote locations. Thanks to it, computers located inside locations can communicate securely over the public Internet as they were located on the same private network. This is accomplished by tunnels that interconnect remote locations. Tunnels add extra layer security, encrypting user traffic carried inside tunnels. […]
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