Someone trying to Hack into my PC

Yesterday when I reviewed my Norton History files there had been 20-30 attempts of "Unauthorised Access Blocked" all in about 1 min, today I had the same thing happening, I click onto the file and see that the "target" is changing from various program files. There is also a shield on the Windows 7 start button that indicates there is updates to be downloaded but there are no updates. Can anyone please assist with this issue.