You should protect your computer from viruses, malware and spamware. Always install official versions of software and download them from the manufacturers sites. Be careful opening attachments of suspicious sources. Office documents can contain viruses. Use an antivirus programm, at least (in case of Windows7) Microsoft security essentials, starting Windows8 security essentialsare included in Windows Defender.
Keep your Firewall activated. A firewall checks for legitimacy of incoming internet traffic. This is a good first protection against hacking.Windows Firewall is included in Windows and activited by default.
Spyware is software that aims to gather information about a person or organization without their knowledge. Windows Defender contains antispyware measures.
Always keep your (Windows) system up to date. Updates contain the latest virus ans spyware protection measures.