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» A basic firewall.

» A Anti-virus software like Kaspersky, AntiVir or Norton, any others may suffice if it contains a virus scanner to scan for malicious software.

» A basic malware removal tool like Ad-Aware or Spybot - Search & Destroy.

» When using a wireless connection, use a robust password.

Medium Business

» A fairly strong firewall.

» A strong Anti-virus software and Internet Security Software.

» For authentication, use strong passwords and change it on a bi-weekly/monthly basis.

» When using a wireless connection, use a robust password.

» Raise awareness about physical security to employees.

» Use an optional network analyzer or network monitor.

Large Business

» A strong firewall and proxy to keep unwanted people out.

» A strong Anti-virus software and Internet Security Software.

» For authentication, use strong passwords and change it on a weekly/bi-weekly basis.

» When using a wireless connection, use a robust password.

» Excercise physical security precautions to employees.

» Prepare a network analyzer or network monitor and use it when needed.

» Implement physical security management like closed circuit television for entry areas and restricted zones.

» Security fencing to mark the company's perimeter.

» Fire extinguishers for fire-sensitive areas like server rooms and security rooms.

» Security guards can help to maximize security.

Government

» A very strong firewall and proxy to keep unwanted people out.

» A strong Anti-virus software and Internet Security Software.

» Strong encryption, usually with a 256 bit key.

» Whitelist authorized wireless connection, block all else.

» All network hardware is in secure zones.

» All host should be on a private network that is invisible from the outside.

» Put all servers in a DMZ, or a firewall from the outside and from the inside.

» Security fencing to mark perimeter and set wireless range to this.

Source: Network security - Wikipedia, the free encyclopedia