From Level 2 to Level 4: The Most Efficient Path to Resilience

1. What Level 2 and Level 4 Mean in Practice #

Level 2: Basic (partially prepared) #

The typical Level 2 state:

• DR plan: exists, last updated 2 or more years ago, never tested
• Backups: run daily, recovery tests rare or never conducted
• RTO/RPO: defined, but never tested against the actual architecture
• Backup access: production admin accounts have access to backup systems
• Air gap: no isolated backup layer
• Offline availability: DR plan exists only in digital form
• NIS2 compliance: not demonstrable

Real risk at Level 2: If ransomware compromises the network and obtains sufficient credentials, online backups are at risk. The Veeam Ransomware Trends Report 2025 found that attackers targeted backup repositories in 89% of attacks. Recovery can take weeks, or fail entirely.

Level 4: Managed (resilient) #

The Level 4 state:

• DR plan: current, tested, with defined roles and a communication plan
• Backups: multi-tier architecture with an air gap layer
• RTO/RPO: defined AND verified through quarterly tests
• Backup access: dedicated backup admin account, no production overlap
• Air gap: physically or galvanically isolated backup layer in place
• Offline availability: DR plan printed and stored securely
• NIS2 compliance: demonstrable through documentation and test records

Real risk at Level 4: Controlled. During a ransomware attack, the air gap layer remains intact. Recovery duration: hours to days, measured and documented.

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2. The Gap Analysis: What Is Missing Between Level 2 and Level 4 #

The move from Level 2 to Level 4 requires four structural changes:

Gap 1: Missing Air Gap Layer #

Problem: All backup copies are network-attached. An attacker with domain admin rights can delete or encrypt them.

Solution: Introduce a physically or galvanically isolated backup layer. With the Silent Brick System, the SB Pro variant provides a physical air gap (bricks are physically removable from the Controller X), while SB Max Air provides galvanic separation without physical removal.

Effort: 4 to 8 weeks (procurement, installation, configuration). One-time.

Impact: Largest single resilience gain. Closes the most common attack path against backup systems.

Gap 2: No Recovery Test Records #

Problem: Backups exist, but no full restore has been tested in the last 12 or more months. The documented RTO is an estimate, not a measurement.

Solution: Quarterly recovery tests with formal records: what was tested, when, how long the restore took, whether it met the RTO target.

Effort: 1 day per quarter for the test, 2 hours for the record. Ongoing.

Impact: Converts the RTO from an assumption to a measured value. Creates audit evidence for NIS2 and, in the financial sector, for the resilience testing obligations under DORA (Regulation (EU) ²⁰²²⁄₂₅₅₄). Surfaces weaknesses in the architecture before an incident does.

Gap 3: Production Credentials for Backup Systems #

Problem: Backup administrators use the same accounts as production administrators. An attacker who compromises production admin credentials automatically has backup admin access.

Solution: A dedicated backup administrator account used for no other purpose, with separate credentials. Ransomware that compromises production credentials then has no automatic access to backup systems.

Effort: 1 day to create and reconfigure.

Impact: Decouples backup security from production security. The cheapest security upgrade per unit of effort.

Gap 4: Outdated and Digital-Only DR Plan #

Problem: The DR plan describes an infrastructure state from three years ago. It also lives on a SharePoint server, which may not be accessible when needed most.

Solution: Annual DR plan updates following infrastructure reviews. Offline availability as a requirement: printed and locked away, or encrypted on media independent of the network.

Effort: 1 day annually for the update. 30 minutes to print and store.

Impact: In an actual incident, you have a plan you can trust, even without network access.

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3. Implementation Path: 12 Weeks to Level 4 #

Weeks 1 to 2: Inventory and Quick Wins #

Immediate actions (zero budget, 0 to 1 day effort):

• Create backup inventory: which systems are backed up? Which are not?
• For each backup: can an attacker with admin credentials delete it?
• Create a dedicated backup admin account (closes Gap 3)
• Print the DR plan and place it in a secure location (partially closes Gap 4)

Outcome after week 2: Gap 3 closed, Gap 4 partially closed. Clear picture of remaining gaps.

Weeks 3 to 4: Planning and Procurement of the Air Gap Layer #

Actions:

• Calculate capacity: data volume times 1.5 as a sizing guideline for air gap capacity
• Decision: physical air gap (SB Pro, removable bricks) or galvanic separation (SB Max Air, automated)?
• Initiate procurement (typical delivery: 2 to 4 weeks)
• Write a backup policy for the air gap layer: frequency, retention, ownership

In parallel:

• Update the DR plan with the current infrastructure state and current contact details
• Document RTO/RPO per critical system if not already done

Weeks 5 to 8: Air Gap Layer Installation and Configuration #

Actions:

• Install hardware and configure networking
• Configure backup jobs: production to online repository, then a backup copy job to the air gap layer
• Run the first test backup to the air gap system
• Set up backup monitoring: failures must trigger immediate escalation

Outcome after week 8: Gap 1 closed. Air gap layer operational. First backups running.

Weeks 9 to 12: Tests, Documentation, Completion #

Actions:

• Run the first full recovery test from the air gap layer
• Measure restore time against RTO targets
• Create a test record (date, tester, system, restore time, outcome, deviations)
• Align the backup concept with your framework of choice: ISO 27001:2022 controls, the NIS2 risk management measures, or, as a national example in Germany, the BSI IT-Grundschutz module CON.3
• Update the DR plan with the new air gap recovery procedure

Outcome after week 12: All four gaps closed. First test records in place. Level 4 achieved.

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4. Budget Frame: What the Move from Level 2 to Level 4 Costs #

Exact figures depend on capacity and vendor, but the order of magnitude is consistent:

• Air gap system: a one-time investment typically in the low five-figure euro range for mid-sized capacity, plus annual maintenance in the low four-figure range
• IT personnel for configuration and tests: a few internal person-days one-time, then roughly one person-day per quarter for tests
• Documentation and DR plan update: 1 to 2 internal person-days one-time, then about half a day per year

For comparison: industry reports put the average cost of recovering from a ransomware attack, excluding any ransom, in the seven-figure range (Sophos State of Ransomware 2025: about USD 1.5 million on average), before reputational damage, regulatory fines, or customer losses. The Level 4 investment pays for itself with the first controlled incident.

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5. What Level 4 Is Not, and Why Level 5 Comes Later #

Level 4 is the foundation on which Level 5 builds:

What Level 4 delivers:

• Demonstrated recovery capability from the air gap layer
• Protection against ransomware that compromises production credentials
• A defensible NIS2 compliance baseline for backup management and disaster recovery
• Controlled failure instead of uncontrolled total loss

What Level 4 does not yet deliver:

• Automated recovery testing
• A full cyber resilience architecture with an isolated recovery environment
• Red-team testing and tabletop exercises as regular practice
• Continuous improvement from post-incident reviews

Recommendation: Reach Level 4 in the first 12 weeks. Then: conduct a first tabletop exercise (a Level 5 element) and evaluate recovery test automation.

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6. Measurement: How to Demonstrate Level 4 #

Level 4 is not self-assessment. It is a measurable property:

• Recovery test frequency: target 4 times per year; evidence: test records with dates
• RTO compliance: target above 90% of tests; evidence: restore time vs. documented RTO
• Backup success rate: target above 99%; evidence: monitoring dashboard, monthly reports
• Air gap backup age: target under 24 hours; evidence: backup job logs
• DR plan currency: target under 12 months old; evidence: version control, date in document
• Backup admin isolation: target 100%; evidence: directory account documentation

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Further Resources #

→ IT Resilience Guide (/en/blog/it-resilienz-leitfaden/) → Resilience Maturity Self-Assessment (/en/blog/resilienz-reifegrad-selbstbewertung/) → NIS2 Audit Preparation: Checklist for IT Managers (/en/blog/audit-preparation-nis2-checklist/​) → Tabletop Exercise Ransomware: Instructions and Scenarios (/en/blog/tabletop-exercise-ransomware/) → Air Gap as a Resilience Layer (/en/blog/air-gap-resilienz-layer/)