This is a quick tip on using a Synology NAS to backup with Time Machine in OSX Lion / Mountain Lion. If you have installed and are running the Synology Antivirus Essentials app, it is advisable to exclude the Time Machine backup location. You can do this by creating and running a ‘custom scan’ instead of running a ‘full scan’. If the antivirus makes any changes to the time machine sparsebundle it will likely cause the backup to become ‘corrupted’ from OSX’s standpoint, which will cause OSX to need to create a full backup again causing the loss of your backup history.
Sophos Antivirus for Mac is a good real-time scanning platform that you can use to protect your OSX based machines and it’s free. http://www.sophos.com/en-us/products/free-tools/sophos-antivirus-for-mac-home-edition.aspx
Bit Defender for Mac is also offered in the Mac app store and as with all Bit Defender products I’ve come across offers solid and superior protection. It’s free and can be used to scan your drives, however I did not see the ability to conduct specific items scans or provide live protection.
Good luck and hope this helps someone out.