[quote=“Dirt Merchant”]I was chatting to my mate online yesterday, only to have him send me one of my pictures, from my PC!
I asked him how the bugger he did that, as I thought he didn’t and shouldn’t have access to my PC. He said he checked my IP address, and went from there. We’re not network-linked in any way.
How did he do it? And how do I stop him, and anyone else, doing it again.
His intentions were not malicious, but nonetheless, my PC is my PC and I want it to stay that way![/quote]
Once he has your IP address, he can scan your computer for open ports. Ports are basically little digital doorways into your computer. Every program that uses TCP/IP uses a port to establish a connection. For example, you use port 80 for http requests, port 21 for ftp requests, et cetera. These are just the default ports. You can tell your FTP program to use any port you want. (If you’re using WS_FTP, just click on the Advanced tap under Session Properties. ) Hell, you could also tell your browser to use a different port by typing in the address and putting a colon and the new port number like, “*ttp://www.anyaddress.com:anynumber” I used to run a web server through an alternate port because my service provider blocked port 80 to keep people like me from running web servers.
So anyway, your friend most likely has a program that allows him to upload and download files through any open port he specifies. Such programs are ubiquitous. If you have a router, make sure all of your ports are closed and/or hidden. Another open door to your computer is through file or print sharing. Make sure this is disabled. (Definitely get a firewall.)