When Wifi first came to the internet world, a lot of people were very conscious of security and everybody seems to be concerned on how secure their network is. A lot of people are constantly war-driving, scanning areas for open internet connections via network access points. These people uses open networks to do hacking, uploading viruses and other malicious stuffs, others, simply take a piggy-back on the free internet connection. Nowadays, you can buy a cheap $6 device that can scan an area for any possible wireless hot spot and you can check if this wireless is open or not by simply opening your laptop and logging in.
Public Wifis in coffee shops and malls are networks that were setup by professional network administrators and security was on their top of their list and should not be compared to a home-based setup.
Usually, when you buy a wireless router, you can simply plug it in, click here and click there using the provided instruction and you are all set, a complete wireless connection inside the house or office… or is it just the house or office?
Through the years, I have been seeing networks that are unsecured and basically open to the public, and what shocks me is there are shared folders that has the write-capability. Also, people tend to forget or actually do not know that wireless routers has strong signals that can actually announce signals farther than they expect, which poses security risk and possible virus infection.
Some people sometimes shares a folder/directory on a network and brings home the laptop, leaving the directory open to the public, connects to the unsecured wireless network, giving access to whoever would connect to the unsecured network. Imagine if somebody who has bad intentions finds that you have an “open to the public” directory and plants a virus? What if a person who has a worm infected computer sees an open connection and jumps in to your network? There are many possibilities that you can get an infection due to carelessness or due to not knowing that you have to add security to your network.
HP Released a very good article guide on 10 steps on how to secure your network, you can view this from this link http://h71036.www7.hp.com/hho/cache/387479-0-0-225-121.html
You can also see a guide at Practically Networked for an in-depth tutorial
http://www.practicallynetworked.com/support/wireless_secure.htm
Some steps you can do to secure your network according to Rediff:
1. Change default administrator usernames and passwords
Most routers or access points come enabled with a default set of username / password combinations. These combinations are well documented and available online for hackers to use. If a hacker can access your device’s administrative pages they can modify the configuration and control all aspects of your device. These username / password combinations can be changed from the administrative panel and should be set to something difficult to guess.
Keep a password which is difficult to guess and not easy to crack. A good password is 8 characters long, not easily guessable, contains mixture of uppercase and lowercase letters as well as numbers and preferably contains special characters like $,*,%,!.
2. Turn on encryption
All wireless devices support some form of encryption. Encryption technology scrambles messages sent over the air and ensures that they cannot be intercepted by hackers. Several encryption technologies exist for wireless communication today. WPA is the strongest commonly available encryption technology for home devices. While WEP can also be used cracking WEP is just a matter of few minutes.
We would advice corporates to go for WPA with EAP Authentication, TKIP / RC4 Encryption or WPA 2 with EAP Authentication, AES-CCMP encryption for better security
3. Change the default SSID
Access points and routers all use a network name called the SSID. Manufacturers normally ship their products with the same SSID set for all routers. For example, the SSID for Netgear devices is normally ‘NETGEAR’. The default SSID can be changed from the administrative panel and should be set to something unique.
4. Enable MAC Address filtering
Each wireless device possesses a unique identifier called the physical address or MAC address. Access points and routers keep track of the MAC addresses for all devices that connect to them. Wireless routers offer the option to key in the MAC addresses of your home equipment so as to restrict the network to only allow connections from those devices.
It ensures that rogue users cannot connect to the wireless router without using advanced MAC spoofing techniques.
5. Disable SSID Broadcast
The wireless access point or router typically broadcasts the network name (SSID) over the air at regular intervals. This feature was designed for businesses and mobile hotspots where wireless clients may roam in and out of range. For the home user, this roaming feature is unnecessary, and it increases the likelihood someone will try to log in to your home network.
Fortunately, most wireless access points allow the SSID Broadcast feature to be disabled by the network administrator. Your SSID name can be manually entered into your devices to prevent the need for SSID Broadcasts to be enabled.
6. Do not auto-connect to open wireless networks
Connecting to an open wireless network such as a free wireless hotspot or your neighbour’s router exposes your computer to security risks and attacks. Although not normally enabled, most computers have a setting available allowing these connections to happen automatically without notifying the user. This setting should not be enabled except in temporary situations.
7. Assign static IP addresses to devices
Most home wireless devices use dynamic IP addresses. DHCP technology is indeed easy to set up. Unfortunately, this convenience also works to the advantage of network attackers, who can easily obtain valid IP addresses from your network’s DHCP pool.
Turn off DHCP on the router or access point, set a fixed IP address range instead and then configure each connected device to match. Using a private IP address range (like 10.0.0.x) prevents computers from being reached directly from the Internet.
8. Enable firewalls on each computer and router
Modern network routers contain built-in firewall capability, but the option also exists to disable them. Ensure that your router’s firewall is turned on. For extra protection, consider installing and running personal firewall software on each computer connected to the router.
9. Position the router or access point safely
Wireless signals normally reach to the exterior of a home. A small amount of signal leakage outdoors is not a problem, but the further this signal reaches, the easier it is for others to detect and exploit. Wireless signals often reach through neighboring houses and into streets. When installing a wireless home network, the position of the access point or router determines its reach.
Try to position these devices near the centre of the home rather than near windows to minimize leakage. Many routers allow you to reduce the range of your router from the administrative panel to prevent the signal leakage.
10. Turn off network during extended periods of non-use
The ultimate in wireless security measures, shutting down your network will most certainly prevent outside hackers from breaking in! While impractical to turn off and on the devices frequently, at least consider doing so during travel or extended periods of downtime.
Viruster 
Literally, 
The other potential threat is 
Browser hijackers are small programs that gets installed in your computer that will literally take control of your browser. Usually what these malicious program does is it embeds its own site as your default homepage, and you have no way of changing it. There are some that gives out errors when you try to change the default homepage, some allows you to change it but reverts back the fake homepage, others will make the browser settings grayed out so you cannot change it.
Why are people creating these kinds of program?
