Suggest an editImprove this articleRefine the answer for “Which OSI layers does network security affect?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**Network security affects all layers of the OSI model**, because attacks and defenses can occur at any stage of data transmission, from the physical cable to the user application. **Key point:** there is no single "security layer" - protection is distributed across the whole OSI model.Shown above the full answer for quick recall.Answer (EN)ImageNetwork security **affects all layers of the OSI model**, because attacks and defenses can occur **at any stage of data transmission**, from the physical cable to the user application. It is important to understand: *there is no single "security layer" - protection is distributed across the whole OSI model.* --- ## Short answer for the interview If you need a short answer: > *Network security affects all 7 layers of the OSI model, because threats and defense mechanisms exist at every layer, from physical to application.* --- ## Layer by layer, in plain terms ### 1. Physical layer **What is protected here:** cables, ports, equipment. **Threats:** - physical access to the server; - disconnecting a cable; - theft of equipment. **Defenses:** - access control to the server room; - video surveillance; - locks, safes. This is mostly about *physical security*, but it directly affects the network. --- ### 2. Data Link layer **What happens here:** frame transmission inside the local network (MAC addresses). **Threats:** - MAC spoofing; - ARP spoofing; - local network eavesdropping. **Defenses:** - port security on switches; - ARP protection; - network segmentation (VLAN). --- ### 3. Network layer **What happens here:** routing, IP addresses. **Threats:** - IP spoofing; - network scanning; - DDoS attacks. **Defenses:** - firewall; - IP filtering; - ACL (access control lists). This is **one of the key layers of network security**. --- ### 4. Transport layer **What happens here:** data transfer between nodes (TCP / UDP). **Threats:** - SYN flood; - session hijacking; - port attacks. **Defenses:** - stateful firewall; - session control; - connection limits. --- ### 5. Session layer **What happens here:** managing sessions and connections. **Threats:** - session hijacking (interception); - session reuse. **Defenses:** - session lifetime control; - re-authentication; - secure token management. --- ### 6. Presentation layer **What happens here:** encoding, compression, data encryption. **Threats:** - interception of data in plain form. **Defenses:** - data encryption (TLS, SSL); - data format protection. This is exactly where **confidentiality** is ensured. --- ### 7. Application layer **What happens here:** the work of applications and services (HTTP, FTP, SMTP and others). **Threats:** - SQL injection; - XSS; - phishing; - attacks on web applications. **Defenses:** - WAF (Web Application Firewall); - user authentication; - input validation. **The most attacked layer**, because it is closest to the user. --- ## Summary in plain terms - Attacks happen **at all layers of the OSI model** - So security must also be **multi-layered** - The higher the layer, the closer the attack is to the user and the dataFor the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.