Your computer is up to date and has latest anti-virus software. You are also protected by firewall and against spyware. For no fault of yours, your internet services get disturbed. For a very long time, we all thought that as long as our computer is secure, it doesn’t matter if your neighbor’s computer is not secure because it is their problem.

Welcome to the world of ARP spoofing.

Internet and local network mostly runs on Ethernet and Wi-Fi. If you are connected through wireless or Ethernet cable, you are using ARP for connecting to other computers and Internet. In other words, your network depends on ARP to function properly.

ARP assumes that every computer in the network is trustworthy. If a computer announces its IP address, every other host MUST accept it. There is little or no way of stopping a computer from announcing a wrong IP address. If a computer, either infected with a virus or not, announces that all IP addresses in the network belongs to it there is no stopping.

Man in the middle attack

For your Internet to work, your computer sends packets to default gateway IP address. What if some other computer sits in the middle and read everything you do on the Internet?

Spoofing computer tells your gateway that it is your computer and tells you that it is the gateway. Obliging, your gateway sends packets to spoofing computer assuming it is your computer. Your computer also falls for the trick and sends the data to the spoofing computer.

Now the spoofing computer controls your internet activity. It not only knows what you are doing on the internet but can change data coming from the Internet. It can modify the web pages you see in the browser. One such activity by a virus known as Win32/Virut.A is creating havoc all over the world. This virus simply inserts the following line into every web page your browse.

Do you have this problem already? Check web page source.

Your computer need not be infected with virus for this to happen.
All your internet activity is controlled by some one else. This includes private messages you send, the credit card you use and much more.

Symptoms of Win32/Virut.A

• Downloads stopped in the middle with connection reset
• Some websites strangely do not open for some