Can ransomware affect OneDrive?
Short answer
Yes, ransomware can affect data in cloud storage services like OneDrive if files connected to an infected system become encrypted. When ransomware executes, it scrambles files across reachable systems, rendering data unusable. Because connected file stores can reflect these modifications, guidance from CISA recommends maintaining offline, encrypted backups rather than relying solely on continuously connected cloud storage.
The details
Ransomware is designed to encrypt files on a system, rendering data and dependent operations unusable until decrypted. When local storage environments connect to cloud storage services, modifications made by malicious software can propagate to those files. A common operational mistake is treating connected cloud file storage as a complete disaster recovery strategy, which leaves organizations exposed if synced directories are impacted during an incident.
To protect mission-critical services, CISA guidance emphasizes maintaining offline, encrypted backups and routinely testing them, aligning with the 3-2-1 backup rule. Organizations should also review their provider documentation directly to verify what version-history, rollback, or file retention settings are active on their accounts, as continuous synchronization tools differ fundamentally from isolated, offline backup copies.
What to do
- Disconnect affected machines from local networks and the internet immediately to halt spread.
- Check your cloud storage provider documentation to verify file restore and version-history capabilities.
- Report ransomware incidents to law enforcement entities such as IC3 or a Secret Service Field Office.
- Maintain offline, encrypted backups and routinely test recovery procedures to verify data availability.
- Apply software updates and operating system patches routinely to reduce vulnerable entry points.
Terms explained
- Backup (3-2-1 rule)
- A backup is a separate copy of data that can be restored after deletion, failure or attack. The 3-2-1 rule means three copies, on two types of storage, with one off-site.
- HTTPS and TLS
- HTTPS is HTTP protected by TLS encryption, which keeps data between a browser and a website private and tamper-resistant and confirms the site controls its domain.
- Ransomware
- Ransomware is malware that encrypts or steals data and demands payment to restore access or prevent publication.