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Security

A collection of 18 posts

Configuring Dynamic NAT on Cisco Routers

Configuring Dynamic NAT on Cisco Routers

Welcome to another tutorial on Network Address Translation (NAT). In this post we'll be looking at how to configure Dynamic NAT on Cisco routers. I highly recommend that you first read through my previous post on configuring static NAT before continuing with this one. What is Dynamic NAT?

NAT (Network Address Translation)

NAT (Network Address Translation)

NAT (Network Address Translation) NAT stands for Network Address Translation. It's one of those concepts that you need to understand if you want to pass your CCNA. Not only do you need to understand how it works, but you also need to know how to configure it. First

DoS TCP SYN Attack Mitigation

DoS TCP SYN Attack Mitigation

A DoS (Denial of Service) attack is an attempt to make a machine or network resource unavailable to its intended users. One common type of DoS attack is the TCP SYN flood attack, which exploits the TCP three-way handshake process. Understanding TCP SYN Flood Attacks In a normal TCP connection

Mitigating SubSeven attacks

Mitigating SubSeven attacks

SubSeven – aka: Sub7 and Sub7Server is a backdoor program, in the form of a Trojan, used mostly for causing trouble on computer networks. It can be used for simple attacks such as hiding the mouse cursor and opening applications, but it can also be used for more serious attacks including

Decrypting Type 7 Passwords (enable password)

Decrypting Type 7 Passwords (enable password)

Cisco passwords are often stored in hashed or encrypted format in the configuration. The different types of password encryption supported by Cisco devices are: * Type 0 (Cleartext) - The password is stored in plain text and is easily readable. * Type 5 (MD5 hash) - The password is hashed using MD5.

Mitigating Smurf DoS Attacks

Mitigating Smurf DoS Attacks

A smurf attack is a form of denial of service (DoS) attack that takes advantage of IP broadcasting and ICMP ping requests to overwhelm a target host with traffic. The attack works by sending ICMP echo requests (ping packets) to a network's broadcast address, with the source IP

IP Address Spoofing Mitigation with Access Control Lists (ACL)

IP Address Spoofing Mitigation with Access Control Lists (ACL)

Understanding IP Spoofing IP spoofing is a technique used by attackers to disguise their identity by modifying the source IP address in packet headers. This makes it appear as if the traffic is coming from a trusted source when it's actually originating from a malicious host. Common attack

Restricting access to Telnet and SSH

Restricting access to Telnet and SSH

By default, when you configure Telnet or SSH on a Cisco router or switch, any device that can reach the management IP address can attempt to connect. This poses a security risk, as unauthorized users could potentially gain access to your network equipment. To enhance security, you can restrict which

Cisco Access-lists (ACL's - Access Control Lists)

Cisco Access-lists (ACL's - Access Control Lists)

Access Control Lists (ACLs) are packet filters. They are a list of conditions that categorize packets. They can be helpful for security and for managing traffic flow. For security, ACLs can allow or deny packets to move through the network. For traffic flow management, ACLs can identify traffic that needs

Port Security on a Cisco Switch

Port Security on a Cisco Switch

What is Port Security? Port security is a feature available on Cisco Catalyst switches that allows a network administrator to configure individual switch ports to allow only a specific number of source MAC addresses to be learned on that port. This prevents an attacker from connecting a device such as

Cisco Router Login Lockdown

Cisco Router Login Lockdown

This post covers various security features built into Cisco IOS that help prevent unauthorized access to your Cisco router or switch. While these features won't stop a determined attacker with physical access to your device, they will provide some basic protection against network-based attacks and casual snooping. Login

'Login local' on a Cisco Router

'Login local' on a Cisco Router

When configuring access to a Cisco router, you have several options for authentication. One common method is using login local, which authenticates users against locally configured usernames and passwords stored on the router itself. What is Login Local? The login local command tells the router to authenticate users using the

Configuring SSH (Secure Shell) on a Cisco device

Configuring SSH (Secure Shell) on a Cisco device

SSH (Secure Shell) provides a secure way to connect to and manage network devices remotely. Unlike Telnet, which sends data in plain text, SSH encrypts all communication between the client and server, making it the preferred method for remote administration. This guide will show you how to configure SSH on

Setting the enable password and secret on a Cisco device

Setting the enable password and secret on a Cisco device

The enable password and enable secret are used to restrict access to privileged EXEC mode (also known as enable mode) on Cisco devices. Let's explore the differences between them and how to configure each. The difference between enable password and enable secret Both the enable password and enable

Configuring the Console port on a Cisco Device

Configuring the Console port on a Cisco Device

The console port on a Cisco device is primarily used for out-of-band management. This is usually the primary method of configuring a device for the first time. All Cisco routers and switches have a console port. Let me show you how to configure the console port on a Cisco device.

Hashing, What is it and how does it work?

Hashing, What is it and how does it work?

Hashing, often referred to as a hash function, is a fundamental concept in computer science and cryptography. It's a mathematical algorithm that takes an input (or 'message') of any size and produces a fixed-size string of characters, which appears random. This output is called a hash

Ports and their use.

Ports and their use.

Ports can be a confusing subject at first, and in this post I hope to clarify what ports are and how they are used. First, let's look at what a port is. A port is a logical connection point. In the networking sense, it is used to identify

How encryption works

How encryption works

Encryption is the process of converting readable information into a scrambled code that hides the information's true meaning. The purpose of encryption is to protect digital data confidentiality as it's stored on computer systems and transmitted using the internet or other computer networks. The outdated data