--- title: "Logical vs. Physical Air Gap: The Difference That Matters When It Counts" date: 2026-03-31T13:40:00+02:00 author: FAST LTA canonical_url: "https://www.fast-lta.de//en/blog/logischer-vs-physischer-air-gap-der-unterschied-der-im-ernstfall-zählt" section: "Entries: Articles" --- ### Logical Air Gap: Definition and Limits [\#](#logical-air-gap-definition-and-limits "Logical Air Gap: Definition and Limits") #### What Is a Logical Air Gap? [\#](#what-is-a-logical-air-gap "What Is a Logical Air Gap?") A **logical air gap** means that two networks are separated by software mechanisms: - **VLAN segmentation:** Backups reside in a separate VLAN, production systems in another. A router or switch does not automatically route data between them. - **Firewalls/ACLs:** Explicit deny rules block traffic between the networks. - **Separate subnets/IP ranges:** Backups have a separate IP network, unreachable at Layer 3. This looks secure. But it is only an air gap on paper. #### The Problem: Credentials Are Available Across the Network [\#](#the-problem-credentials-are-available-across-the-network "The Problem: Credentials Are Available Across the Network") The critical flaw: backup administrators or backup software need credentials (username, password, API keys) to access the isolated backup network. These credentials are: 1. **Stored locally** on administration PCs or production servers (for example in scripts or configuration files) 2. **Present in RAM** when backup software is running 3. **In the directory service** (if central authentication is used) With admin rights (which ransomware obtains after privilege escalation), attackers can read these credentials with standard tooling, connect to the “isolated” backup network, and delete or encrypt the backups. VLAN and firewall isolation only protect as long as credentials are not compromised. With advanced ransomware, that assumption is unrealistic. #### The “Virtual Air Gap” Myth [\#](#the-virtual-air-gap-myth "The ") Some solutions advertise a “virtual air gap” or “logical air gap.” This is a marketing term without real security substance. It typically means: - Daily automatic disconnection (network interface disabled after backup) - Separate admin accounts (with separate credentials) - Network segmentation This is better than nothing, but still circumventable: - The network interface can be re-enabled by malware with admin rights - The admin credentials can be stolen through the same attack vectors - Network segmentation can be overcome through lateral movement A virtual air gap is not genuine isolation. --- ### Physical Air Gap: Definition and Practical Implementation [\#](#physical-air-gap-definition-and-practical-implementation "Physical Air Gap: Definition and Practical Implementation") #### What Is a Physical Air Gap? [\#](#what-is-a-physical-air-gap "What Is a Physical Air Gap?") A **physical air gap** means that two systems have no network interface through which they can reach each other. The separation is not firewall-based but hardware-based. Two disk-based implementations: 1. **Silent Brick Max Air:** A backup appliance whose connection is galvanically severed in the offline state. Data is written during a controlled backup window, then the connection is electrically cut. No physical removal needed, no manual handling. 2. **Silent Brick Pro:** Storage bricks that are physically removable from the Controller X. Removal creates a physical air gap; the medium itself is offline and not network-addressable. Legacy approaches such as tape removed from a drive or unplugged USB drives also create a physical separation, but they depend on manual media handling, introduce human error, and slow down recovery. Disk-based hardware air gap automates the isolation and keeps restores fast. #### Why a Physical Air Gap Works Against Ransomware [\#](#why-a-physical-air-gap-works-against-ransomware "Why a Physical Air Gap Works Against Ransomware") The logic, compared point by point: - **Network addressability:** Logical air gap: yes, the path exists, only firewall-blocked. Physical air gap: no active interface at all. - **Credentials required:** Logical air gap: yes, and ransomware can steal them. Physical air gap: no, the separation is physical, not credential-based. - **Bypassable with admin rights:** Logical air gap: yes, by changing firewall rules or using stolen credentials. Physical air gap: no, no command can establish a hardware connection that does not exist. - **Ransomware protection:** Logical air gap: moderate. Physical air gap: strong. The practical sequence: ransomware breaks in and escalates to admin rights, then tries to reach the backup target. With a logical air gap it finds credentials, connects, and deletes backups. With a physical air gap there is no network interface, no credentials help, and access is impossible. The attacker can issue thousands of commands on the production side; none of them can create a physical connection to air-gapped hardware. --- ### Practical Examples [\#](#practical-examples "Practical Examples") #### Example 1: Infected Production Network with Logical Air Gap [\#](#example-1-infected-production-network-with-logical-air-gap "Example 1: Infected Production Network with Logical Air Gap") Scenario: ransomware has admin rights on a production server. The attacker searches the file system for stored credentials, finds a backup script containing the backup account and password, mounts the backup share with those credentials, and deletes the backups. VLAN and firewall did not prevent any of it, because the credentials were exposed. Result with logical air gap: the attacker wins. #### Example 2: Infected Production Network with Physical Air Gap [\#](#example-2-infected-production-network-with-physical-air-gap "Example 2: Infected Production Network with Physical Air Gap") Scenario: ransomware has admin rights. The Silent Brick Max Air is offline, galvanically separated. The attacker scans for backup hosts: nothing is online. DNS lookups fail, pings time out, no connection can be established. The backup system is not addressable, regardless of which privileges the attacker holds. Result with physical air gap: the backups survive. --- ### Hybrid Approach: Best Practice [\#](#hybrid-approach-best-practice "Hybrid Approach: Best Practice") A robust strategy combines both: 1. **Production network:** Standard security (EDR, firewall, segmentation) 2. **Backup network (logical air gap):** VLAN segmentation, firewall, separate credentials 3. **Hardware air gap (physical air gap):** Silent Brick Max Air or removable Silent Brick Pro bricks, offline after backup When ransomware breaks in, it can damage layers 1 and 2, but not layer 3, because layer 3 is physically isolated. --- ### Comparison at a Glance [\#](#comparison-at-a-glance "Comparison at a Glance") - **Setup complexity:** Logical: moderate (VLAN, firewall). Physical: higher (hardware integration), but automated in operation. - **Administrative flexibility:** Logical: high (rules changeable). Physical: deliberately rigid; that rigidity is the protection. - **Ransomware resilience:** Logical: moderate (credentials at risk). Physical: strong (not reachable). - **Recovery time (RTO):** Logical: fast. Physical on disk: fast as well; the system reconnects for restore and data is immediately accessible. - **Cost:** Logical: low (software). Physical: higher (hardware), offset by drastically reduced incident risk. - **Compliance suitability:** Both can be documented; security agencies recommend offline copies, and a physical air gap is the stronger evidence. --- ### Frequently Asked Questions [\#](#frequently-asked-questions "Frequently Asked Questions") **Is a logical air gap secure at all?**It adds value if credentials are not stored locally but managed centrally in an HSM or vault. Then attackers cannot simply read them. But this is administratively difficult and expensive, and it still leaves a network path in place. **Can I have a physical air gap with automated backups?**Yes. The Silent Brick Max Air automates the process: backup runs on schedule, data is written, the connection is then galvanically severed. No administrator intervention required. **Do I need a physical air gap if my backup network is not reachable from the internet?**That helps, but not against insider threats or ransomware that enters from the production network. A physical air gap is the strongest defense. **What about an air gap on a single server?**Not practical. An air gap only works at the hardware/network level. A single server with shared resources is not an air gap. --- ### Further Resources [\#](#further-resources "Further Resources") → How Ransomware Destroys Backups: Technical Analysis (/en/blog/wie-ransomware-backups-zerstoert/) → Hardware Air Gap: Comparison for IT Decision-Makers (/en/blog/hardware-air-gap-vergleich/) → Silent Brick System: Backup Storage with Hardware Air Gap (/en/produkte/silent-brick-system/) → Ransomware Protection: Guide for IT Decision-Makers (/en/blog/ransomware-schutz-leitfaden/) → Request a Demo (/en/kontakt/demo/) ### Air Gap An air gap is the complete physical interruption of all network connections between a backup system and the rest of the IT infrastructure, so that the system has no addressable network interface in its offline state and is therefore unreachable by ransomware and attackers. [Mehr erfahren →](https://www.fast-lta.de//en/glossary/air-gap) ### Ransomware Ransomware is malware that encrypts data on infected systems and demands a ransom for decryption — with the goal of forcing organizations and public bodies to pay by paralyzing their operations. [Mehr erfahren →](https://www.fast-lta.de//en/glossary/ransomware) ### Ransomware Ransomware is malware that encrypts data on infected systems and demands a ransom for decryption — with the goal of forcing organizations and public bodies to pay by paralyzing their operations. [Mehr erfahren →](https://www.fast-lta.de//en/glossary/ransomware) ### Air Gap An air gap is the complete physical interruption of all network connections between a backup system and the rest of the IT infrastructure, so that the system has no addressable network interface in its offline state and is therefore unreachable by ransomware and attackers. [Mehr erfahren →](https://www.fast-lta.de//en/glossary/air-gap) ### Air Gap An air gap is the complete physical interruption of all network connections between a backup system and the rest of the IT infrastructure, so that the system has no addressable network interface in its offline state and is therefore unreachable by ransomware and attackers. [Mehr erfahren →](https://www.fast-lta.de//en/glossary/air-gap) ### Ransomware Ransomware is malware that encrypts data on infected systems and demands a ransom for decryption — with the goal of forcing organizations and public bodies to pay by paralyzing their operations. [Mehr erfahren →](https://www.fast-lta.de//en/glossary/ransomware) ### Disaster Recovery Disaster recovery refers to the structured processes and technical measures that ensure IT systems can be restored within defined timeframes (RTO) with maximum data loss (RPO) after a severe failure — ransomware attack, hardware failure or data center outage. [Mehr erfahren →](https://www.fast-lta.de//en/glossary/disaster-recovery) ### Ransomware Ransomware is malware that encrypts data on infected systems and demands a ransom for decryption — with the goal of forcing organizations and public bodies to pay by paralyzing their operations. [Mehr erfahren →](https://www.fast-lta.de//en/glossary/ransomware)