Network Security — Threats and Protection

Connecting a computer to a network, and especially to the Internet, brings great benefits but also exposes it to threats — harmful programs and attacks that can damage data, steal information, or misuse the system. Network security means the steps taken to protect a computer, its data, and the network from these dangers.

A. Malware — harmful programs. Malware (malicious software) is any program written to harm a computer or its data. The main kinds are:

• Virus. A program that attaches itself to a file or program and, when that file is run, copies itself to other files and spreads. A virus can corrupt or delete data, slow the computer, or make it behave wrongly. It needs the user to run the infected file to spread.
• Worm. A program that copies itself and spreads across a network on its own, without needing to attach to another file, often clogging the network and slowing computers.
• Trojan horse. A harmful program that hides inside something that looks useful or harmless (a game or a free tool); when the user runs it, it secretly damages the system or lets an attacker in.
• Spyware. A program that secretly watches what the user does and sends private information (such as passwords) to someone else without permission.

B. How infections spread and how to prevent them. Malware usually spreads through infected e-mail attachments, downloads from unsafe websites, infected pen drives, and pirated software. Ways to prevent infection and protect a networked computer include:

1. Install and update antivirus software to detect and remove malware.
2. Keep the operating system and software updated, so security holes are closed.
3. Do not open unknown e-mail attachments or links, and do not download from untrusted sites.
4. Scan pen drives and external devices before use.
5. Use strong passwords and change them from time to time.
6. Take regular backups of important data, so it can be restored if damaged.
7. Use a firewall (see below) to control network traffic.

C. Cookies. A cookie is a small text file that a website stores on the user's computer through the browser to remember information about the user — such as login details, items in a shopping cart, or preferences — so the site can recognise the user on the next visit. Cookies make websites more convenient, but because they record browsing information they also raise privacy concerns, and users can view or delete them in the browser settings.

D. Firewall. A firewall is a security system — hardware, software, or both — that sits between a computer or network and the outside Internet and controls the traffic passing in and out, according to set rules. It allows safe, permitted data through and blocks unauthorised or harmful access, acting like a security guard at the gate of the network. It is a first line of defence against attacks from outside. …