Help me please

Hello.
I have had two accounts of mine hacked: minecraft and Skype. The mine craft account was hacked a couple months ago, and I thought little of it. Then one of my friends on Skype got hacked, and then I got hacked just this weekend. The hacker sent a file out to all of my contacts that was dangerous, I don't know exactly what it was. At the moment, I am experiencing no unusual problems but I don't know whether something is in my computer that is accessible to the hacker and I don't know where to look or how to get rid of it. I have a mac running lion. Please help if you know anything about situations like this. Thanks.
-chris

Hi  

Oops forgot to add it sounds like you have a Virus or a Trojan...

All the best Brett  

Hello.
I have had two accounts of mine hacked: minecraft and Skype. The mine craft account was hacked a couple months ago, and I thought little of it. Then one of my friends on Skype got hacked, and then I got hacked just this weekend. The hacker sent a file out to all of my contacts that was dangerous, I don't know exactly what it was. At the moment, I am experiencing no unusual problems but I don't know whether something is in my computer that is accessible to the hacker and I don't know where to look or how to get rid of it. I have a mac running lion. Please help if you know anything about situations like this. Thanks.
-chris

Here is an account of a friend of mine of what happened. http://www.tomshardware.com/forum/38030-63-undetectable...
Also, I made a new Skype account, and it too was hacked.
What are some good free programs that I can run to hopefully get rid of this or what other steps should I take?

It sounds like some kind of malicious software, to be in safer zone try comodo antivirus software.

Hey guys,
Thanks for the help. I ended up erasing my hard drive and resetting my mac, but I also transferred files through a backup disk. They were all pictures and music. Malicious software could not hide inside those could it? I am also turning on mac security features such as file vault and I will be buying a reputable anti virus software soon. I would just like to make sure that the virus is completely gone. Is erasing the hard drive a way to do that? I haven't been touched since I erased the hard drive, but I want to be absolutely sure that it is gone. Thanks again.Sophos is a free anti virus program and it works. try it before buying anything and wasting your money.
-chris