The internet can be a dangerous place, regardless of whether you are a light or heavy user. Hackers, automated systems and other types of intrusions constantly scan computers that are on the internet to try and break into them to steal information and create havoc wherever possible. Sometimes it's difficult to tell if unwanted IP addresses are accessing your computer, unless you know what types of tricks and software will give you the edge.
Use the netstat command on Windows operating systems to get a list of what programs are accessing what IP addresses through which ports on your computer. To use netstat, open a command line by clicking the Start button, clicking on the Run option and typing "CMD" into the Run box and clicking the OK button. Type "netstat" into the command line window to see the list of programs, IP addresses and ports that are connecting to the web.
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Install firewall software on your computer that will alert you to what types of incoming and outgoing connection attempts are occurring on your computer. Using a third-party firewall software will give you a great deal of flexibility in this area, since most applications will give you the option to set up popup alerts that appear when unknown or unwanted IP addresses attempt to connect to your computer.
Install and run a packet sniffing application like Wireshark or Ethereal which will show you the packet-level communications to and from your computer. Included in the packet will be information about what IP addresses are sending and receiving information to and from your computer. Running this type of software requires an advanced technical understanding of computers, so it may require that you seek out the help of a qualified individual for assistance.