detection and backups are two separate things.
- the antivirus will help you detect (and clean if possible) that something is wrong
- the backups will help you restore after any damage happened
if you only have an anti-virus and no backup, you will lose stuff if a virus goes through the AV checks.
if you only have a backup system, you could be losing stuff as we speak, without knowing. or you could be hosting an army of trojans etc.
For all you know, your backups could be infected. As was mentioned above, if you didn't keep all your backups, chances are you won't be able to find one not infected
Best is to have both. But in any case AV > Backup.
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