How do you know if you system has been Hacked?

Good article from SANS

1. Your anti-virus program has triggered an alert that your system is infected, particularly if it says that it was unable to remove or quarantine the affected files
2. Your browser’s homepage has unexpectedly changed or your browser is taking you to websites that you did not want to go to
3. There are new accounts on your computer or device that you did not create, or new programs running that you did not install
4. Your computer or applications are constantly crashing, there are icons for unknown apps, or strange windows keep popping up
5. A program requests your authorization to make changes to your system, though you’re not actively installing or updating any of your applications
6. Your password no longer works when you try to log into your system or an online account, even though you know your password is correct
7.  Friends ask you why you are spamming them with emails that you know you never sent
8.  Your mobile device is causing unauthorized charges to premium SMS numbers
9.  Your mobile device suddenly has unexplained very high data or battery 

PDF Link Below

https://securingthehuman.sans.org/newsletters/ouch/issues/OUCH-201604_en.pdf