My IP address is banned by some of the websites because of doing email spam and dictionary attack. But I think I am not involved in these activities. I think someone else will be using MY IP as his own IP address as we use proxy sites. But it is only possible if one can access my IP address from his own system and if he can use it.
closed as off topic by danlefree♦ Jan 29 '12 at 18:01
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Most bot networks possess innocent user computers and infest them with hidden malware that is usually used to send unsolicited email, among other things.
You might want to run some spyware cleaning software and anti viruses, also having a firewall where you need to approve outgoing requests might help find the culprit.
Other than that, if you are using a shared IP address, it could be any of your neighbors on the network that are either doing this activity, or have infected computers.