In case you have any doubts:
Norton Antivirus (made by Symantec) has a very long and illustrious reputation for mangling Mac OS X systems, sometimes to the point where a complete reinstall is necessary. Among other things, it installs kernel extensions which are known to cause kernel panics and system freezes; it contains known and documented bugs which can silently corrupt Adobe Photoshop and Adobe InDesign files, destroy a user's ability to authenticate as an administrator, and (on PPC systems) can cause Classic to stop functioning; and Symantec has on at least two occasions now released flawed .dat file updates which erroneously report certain critical Mac OS X files as "viruses." (Deleting these "viruses" causes damage to the system that in some cases renders it unbootable.)
Norton has also been reported as damaging iPhone backups.
A major security flaw in Norton has also been noted:
http://www.macnn.com/articles/15/05/08/contentious.utility.ignored.apple.guideli nes.created.zero.day.exploit.128538/