Need an expert to check if I have illegal activity on my network please

wwell.. I switched to linux becuase I was being targeted by hackers on windows BIG TIME...it was so bad that my pc wasnt even mine.. it was simply a thin client to locon the hackers network.. I just want to be sure im still not being infiltrateed

Another indicator is its failing to download updates any advice??

hers the details on the update failure..

W:The repository 'cdrom://Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1) xenial Release' does not have a Release file., Wata from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., E:Failed to fetch cdrom://Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)/dists/xenial/main/binary-amd64/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update caot be used to add new CD-ROMs, E:Failed to fetch cdrom://Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)/dists/xenial/main/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update caot be used to add new CD-ROMs, E:Some index files failed to download. They have been ignored, or old ones used instead.