System Securiy

Introduction

Networking brings a great range of advantages, which we have already discussed. However, because networked computers are always connected to one another, it means that if someone is able to access one computer, they could in fact access all data on all devices on the entire network! Criminals will do all that they can to gain entry to a network for this very reason. It is therefore vital that we understand these risks and have in place measures to reduce them.

Malware

Malware is any software which can harm a computer or user. There are a range of different types of Malware:

Viruses

Spyware

Adware

Pharming

Viruses

Viruses are small programs which aim to cause physical harm to a computer system.  They often get confused with spyware (which simply spy on users, recording key strokes etc. but do not aim to harm the system – just the user).

The main types are:

Standard Virus

These hide in files / programs and replicate themselves in order to spread into other programs / files. Their aim is usually to delete or damage data.

Worms Virus

These don’t necessarily damage data, instead they simply try to replicate themselves, using more and more of the computer’s resources, slowing down your computer and making it useless.

Trojan Virus

These are often programs (such as a game) which you can use. But in the background they will cause harm, like deleting your files, making annoying changes to your computer setup or creating a portal for other users to use in order to gain access to your system.

Spyware

Spyware’s aim is to spy on the user and send back as much information about them as possible (passwords, usernames, websites they visit, purchases they have made). A common piece of spyware is a key logger. It quietly runs in the background recording every key you hit. If you type in the same set of characters, regularly, this could be identified as your password. The reason for collecting this data is so that ‘senders’ of the spyware can use this information to steal your identification or sell your information to third parties who will then target you with advertisements.

Adware

Like spyware, this type of malware doesn’t physically delete or corrupt a system’s data. Instead its aim is to download and display unwanted adverts and collect marketing information about your online habits. It will often also try to direct you to unwanted websites by changing your default homepage.

Pharming

We have already seen how a DNS server enables us to ‘lookup’ the IP addresses of computer that are hosting website…so that we can then visit them. Pharming malware seeks to change the IP address stored in the DNS (or cached on our computer) to another IP address so that the user is sent to a phoney website instead of the one they intended. For example, if we typed in www.bbc.co.uk into our browser, this URL would be looked up on the DNS and the IP address…