Ransomware Defense Basics Cheat Sheet
Backup strategy, segmentation, detection signals, and incident response steps to prevent and recover from ransomware attacks.
2 PagesBeginnerMar 27, 2026
3-2-1-1 Backup Verification
Script sketch to confirm an offline/immutable backup copy actually exists and restores cleanly.
bash
# 3 copies, 2 media types, 1 offsite, 1 immutable/offline# Verify latest immutable backup snapshot exists (example: AWS Backup vault lock)aws backup list-recovery-points-by-backup-vault \ --backup-vault-name immutable-vault \ --query 'RecoveryPoints[0].{Status:Status,CreationDate:CreationDate}'# Periodically test-restore into an isolated sandbox account/VPC# and checksum the restored data against a known-good hashsha256sum -c restored-data.sha256
Prevention Controls
The controls that stop or slow the initial compromise and lateral spread.
- Immutable backups- object-lock/WORM storage attackers can't encrypt or delete
- Network segmentation- isolate backup infra and critical systems from user VLANs
- MFA everywhere- especially on VPN, RDP, and privileged/admin accounts
- Patch management- prioritize internet-facing and known-exploited CVEs (CISA KEV)
- Least privilege- limit domain admin usage, use tiered admin accounts
- Email/endpoint filtering- block macro-enabled attachments and known malicious domains
Detection & Response Signals
Early indicators and the first response steps if ransomware activity is suspected.
- Mass file renames/encryption- sudden spike in file-extension changes across shares
- Shadow copy deletion- `vssadmin delete shadows` is a near-certain pre-encryption signal
- Unusual outbound traffic- large data transfers before encryption (double-extortion staging)
- Isolate, don't reboot- pull network cable/disable NIC; rebooting can trigger the payload
- Activate IR plan- engage incident response, legal, and law enforcement per playbook
- Restore from clean backup- rebuild from the last known-good immutable snapshot, not in place
Pro Tip
Test your backup restore process quarterly under a simulated ransomware scenario, not just backup completion — most organizations discover their restore is too slow or the backups were also compromised only after a real attack, when it's too late.
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