HijackThis is a utility that produces a listing of certain settings found in your computer. HijackThis will scan your registry and various other files for entries that are similar to what a Spyware or Hijacker program would leave behind. Interpreting these results can be tricky as there are many legitimate programs that are installed in your operating system in a similar manner that Hijackers get installed. Therefore you must use extreme caution when having HijackThis fix any problems. I can not stress how important it is to follow the above warning.
For the past couple of years there has been a new threat introduced to your computer that anti virus software does not as of yet remove. This software is developed to track your movements on the Internet, create statistics of what you do on your computer, or even worse, actually hijack your web connections to direct you to pages that you did not ask for. These types of Malware are called Spyware, Browser Hijackers, and Dialers. Malware is the generic category of any programs that perform a detrimental effect on your computer without your knowledge or permission. Other more notorious types of Malware are viruses, Trojans, worms, and backdoors.
Windows XP comes with a built-in firewall called Windows Firewall. For people who do not want to spend the money on a commercial software firewall, this firewall will be more than enough to protect your computer. By default, Windows Firewall disables all incoming traffic to your computer, including ICMP traffic, which consists of pings. Just like all other firewall's you can specify which services/ports you would like to have open so that other computers can connect to yours. This will allow you to open up ports for services like web servers, mail servers, game servers, etc. Windows Firewall comes configured with basic services that you can enable to be opened, and you also have the ability to add other rules for incoming traffic that are not already configured. If you would like, you also have the ability to enable incoming ICMP traffic, so that you can ping and traceroute to your computer.
One of the top questions I see on forums is "How do I know if I have been hacked?". When something strange occurs on a computer such as programs shutting down on their own, your mouse moving by itself, or your CD constantly opening and closing on its own, the first thing that people think is that they have been hacked. In the vast majority of cases there is a non-malicious explanation for these problems such as faulty hardware or problematic software, but it is better to be safe than sorry for not investigating deeper. Unfortunately, the vast majority of computer users have no idea how to go about determining if their computer is hacked. It is for these people, that I am writing this tutorial.
Anyone who is in the security arena should know about Windows Alternate Data Streams, otherwise known as ADS. Though not highly publicized, lack of this little known attribute of the Windows NTFS file system may affect how you solve a problem in the future.