OSI Layers - Open Systems Interconnection Reference Model
- Application - Provides application connection HTTP, FTP, SMTP, SNMP etc.,
- Presentation - Data formatting and encryption takes place - known as syntax layer - ASCII encoded to EBCDIC Or vice-versa
- Session
- Transport - connects low level communication hardware in level 1 through 3 with higher level software in levels 5 through 7 - TCP, UDP - Communicates in segments
- Network - Sends and receives in Packets (Chunk of data)
- Datalink
Sends and receives frames (a sequence of 64 to 1518 bytes). Two sub-layers:-
MAC - Media Access Control
LLC - Logical link Control (Used by network switches)
7. Physical - Data transmitted in bits. Cable and radio spectrum
Hint:- Please Do Not Tell Sales People Anything to remember OSI layers
Network topology
1) Bus - No central device - only T connector
2) Ring - No central device - only T connector
3) Star - Central device connects each device
4) Mesh - Every device connects to each other
5) Wireless Mesh
Hybrid Topology
2 or more network topology
Point to point communication
Point to multi-point
CIA - Confidentiality Integrity Availability
Risk Identification
Risk Assessment
Quantitative Risk Analysis Vs Qualitative Risk Analysis
Asset Value
Exposure Factor
Single Loss Expectancy = Asset Value (AV) x Exposure Factor (EF)
Annualized Rate Of Occurrence
ALE = SLE x ARO
CVSS (Common Vulnerability Scoring System) Calculator
https://first.org
Risk Response (Take Decision) - Evaluating Counter measures - Provide a proposal - Adjusting the finding
Risk Treatment - Avoid (You can do but are not doing - Ignore) / Accept (You cannot do anything - Accept the existence of vulnerability and move on) / Mitigate (Fix the vulnerability) / Transfer (Risk to the supplier, eg: Cloud Provider to take care)
Goal of Risk Management - Minimise the risk in the org and maintain the same
Residual Risk - Risk which remains after counter-measures (Never Eliminated but lesser in-nature)
Risk Monitor - Contiuous monitoring of the risk - Qualsys , Nessus
Key Performance Indicator (KPI) - How well a process is progressing towards a intends goal
Key Risk Indicator (KRI) - Metrics , which defines risk threshold of an organisation - how many denial of service (DoS) - How many acceptable and not acceptable - eg:- Quantity of unauthorized software , no-antivirus
KPI and KRI are SMART metrics
KPI - underperforming KRI - Early Warning
SMART - Specific Measurable Attainable Relevant Time-Bound
Security Controls: - Policies to protect CIA of the asset - Administrative Controls - no impact to work , security training - Technical Controls - Firewall in-place , Physical Controls - CCTV
Control Types - Detective (sensor) , Preventive (lock) , Deterrant (violating company policies) , Corrective , Recovery Control (Backup) , Compensating (Alternative - Intent , similar level of defense)
Control Selection - High Security in Jewellery Shop , Bank. College - Normal Security
Risk Management Frameworks: NIST , CIA
NIST - National Institute Of Science and Technology (United States Federal Govt)
- Prepare
- Categorize
- Select
- Implement
- Assess
- Authorize
- Monitor
- Identify
- Protect
- Detect Respond
- Recover
