If you get an email saying it is from the court system and you need to appear in court on a certain day, do not open the attachment. The court system wouldn't contact you first through email. This is a scam email that when you open the email attachment, installs malware.
I received an email supposedly from Netflix. It looked very official and used their logos. However, it was sent to an email account I have that Netflix doesn't have. And when I moused over the address of the sender (that said Netflix) it was actually an address in the UK. Please double check before you click on any links on any email messages you receive.
If you get a call from someone saying they are from Microsoft, hang up. Microsoft will not call you and tell you that there is something wrong with your computer.
Always make sure you have an update and active anti-virus program. I also recommend a good malware/spyware cleaner.