Does cloud storage protect against ransomware?
The short answer
A sync drive on its own does not. When ransomware encrypts your files, the sync client uploads the encrypted versions over the cloud copies. What protects you is version history with point-in-time restore. Backup services like Backblaze, IDrive and Acronis let you roll back to before the attack. Sync.com does too, with up to 180 days of versions.
In detail
Many people expect the cloud to stop ransomware. The malware encrypts files on your computer. Your sync client then sees thousands of changed files. It does its job and copies the damage to Dropbox, Google Drive or OneDrive within minutes. Now the cloud copy is encrypted too.
The defense is storage that remembers what your files looked like before. Services differ in how far back they go. OneDrive has built-in ransomware detection. With one click it restores the whole drive to a chosen date within the last 30 days. Dropbox and Google keep version history per file, 30 days as standard. That works well for a few files and takes a long time for ten thousand.
Sync.com keeps up to 180 days of versions on its larger plans. That is a comfortably long window. True backup services are built for exactly this. Backblaze keeps 30 days as standard and can extend that to forever. IDrive keeps up to 30 versions per file. Acronis goes furthest and actively blocks processes that try to tamper with its backup files.
CISA’s ransomware guidance on stopransomware.gov adds one more layer. Keep at least one copy offline or out of reach of an infected machine. Advanced attacks look for connected backups first. At home that can be an external drive that is not always plugged in. A cloud backup that needs separate login details to delete also works. You only have to set this up once. With a versioned cloud backup and an offline drive in a drawer, you can recover from ransomware in an afternoon.