Cosmos DB data which is not moving around the network is encrypted and secured. You can be rest assured that, even if attackers somehow get your stored data, it will be extremely tough for them to decrypt it.

Let's look over the key security features offered by Azure:

• Secured network: Cosmos DB provides an IP-based, rule-filtering firewall for advanced network protection
• Authorization: Cosmos DB authorize users using hash-based authentication codes
• User management: Cosmos DB provides secure user management using the resources concept
• Active directory support: Cosmos DB integrates with widely known and secure active directory authentication systems
• Turnkey distribution and replication: Using turnkey distribution, data is replicated and secured
• Failover handling: You can use automatic or manual failover
• Automated backups: Cosmos DB data is backed up regularly
• Database restoration: You can restore your database from the backup
• Monitor for attacks: By using monitoring, you can monitor attacks if they are happening to your server
• HTTPS/SSL/TLS encryption: All data traveling via the Azure network is encrypted
• Encryption at rest: All data stored in Azure machines is encrypted

Compared to the industry at large, Azure offers some very advanced features.