There are three types of ARP spoofing in the terms of spoofing target.
1. Only host computer is spoofed, with the result as the following chart.

2. Only Router or Gateway is spoofed, with the result as the following chart.

3. The combination of the former two spoofing, with the result as the following chart.

The threat of ARP spoofing can be divided as the following types:
1. Unusual internet connection: IP conflict or frequently lost internet connection.
2. Data leaking: leak of private information( MSN chatting record, emails) or leak of accounts and passwords.
3. Data being changed: Hostile change of website content.
4. Illegal control: Others' illegally control of your connecting speed or your visit to some certain website.

The ARP spoofing can be divided to two types according to the differences of attackers:
1. Artificial attacks. The main aims of artificial attacks are as follows: to cause unusual internet connection, to steal data, to control others' computer illegally.
2. ARP viruses The main application of ARP viruses are as following: to steal data such as passwords, to change website data.

Currently, most of ARP spoofing is discovered after unusual internet connection. Notice: a careful designed artificial ARP spoofing or a well designed ARP virus will not cause unusual internet connection. So it doesn't mean that without unusual internet connection there must be no ARP spoofing to your computer.