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Bayesian Network-Based Privilege Escalation Risk Estimation in Linux Systems Using Vulnerability and Access-Relationship Features

Description

Enterprise organizations commonly use Linux systems to host applications, databases, services, and infrastructure workloads. Linux manages user accounts, groups, file permissions, processes, and system services to control access to system resources.

Privilege escalation occurs when a user or process obtains permissions beyond those intended by the system's access-control policy. Vulnerable software, excessive permissions, insecure configurations, and inappropriate access relationships can contribute to privilege escalation risk.

A vulnerability alone does not always indicate that privilege escalation is possible. The potential risk also depends on the privileges available to a user, the affected services, and the relationships between users, processes, and system resources.

In this use case, an Ubuntu Linux virtual machine is deployed as the assessment target, while Kali Linux is used as the security-testing environment. A controlled Linux privilege-escalation risk assessment is performed using vulnerability information and access-relationship features.

A publicly available security dataset is used to provide vulnerability-related records for the risk-estimation workflow. Linux user permissions, group memberships, services, and access relationships are reviewed to identify relevant security features.

Python and Pandas are used to preprocess the security data. NetworkX is used to represent relationships between users, groups, processes, and system resources. A Bayesian Network implemented using pgmpy estimates privilege escalation risk based on the selected vulnerability and access-relationship features.

Nmap is used to identify network-accessible services where applicable, while OpenSCAP is used to assess the Ubuntu host's security configuration. The estimated risk and validated security findings are documented to support remediation prioritization.

The identified Linux permissions and configuration weaknesses are then reviewed and corrected where necessary. The assessment is repeated to determine whether the observed security risks have improved after remediation.

The complete security-validation workflow is:
Linux System
→
Vulnerability and Access-Relationship Data
→
Security Feature Extraction
→
Access-Relationship Analysis
→
Bayesian Network Risk Estimation
→
Privilege Escalation Risk Assessment
→
Finding Validation
→
Risk Prioritization
→
Linux Hardening
→
Reassessment
→
Security Validation

Existing Security Problem

Application/Service: Linux Operating System

Linux is the target operating system in this use case. It manages user accounts, groups, file permissions, running processes, and system services to control access to system resources.

Existing Problem :

If a Linux system contains vulnerable software, excessive user permissions, insecure file permissions, or inappropriate access relationships, a user or process may have opportunities to obtain privileges beyond those intended by the system administrator.

Reviewing vulnerabilities independently may not provide enough information to understand how existing permissions and access relationships contribute to privilege escalation risk.

A security assessment therefore needs to combine vulnerability-related information with relevant Linux access relationships and use a risk-estimation method to identify and prioritize potentially risky conditions.

The security problem is:
Linux System
→
Vulnerable Software or Configuration
→
Excessive or Inappropriate Permissions
→
Risky Access Relationships
→
Potential Privilege Escalation Path
→
Increased Security Risk
→
System or Data Compromise

The proposed solution introduces vulnerability and access-relationship feature extraction, Linux permission analysis, graph-based relationship representation, Bayesian Network-based risk estimation, security finding validation, risk prioritization, Linux hardening, and post-remediation validation.

Attack

Specific Attack: Linux Privilege Escalation Assessment

The controlled attack scenario evaluates whether identified Linux vulnerabilities and access-control conditions may contribute to privilege escalation risk.

A designated non-privileged laboratory account is used to review permissions, accessible resources, running services, and relevant security configurations.

The objective is to identify and assess potentially risky conditions in the authorized Linux environment. The assessment does not assume that every vulnerability or permission weakness can be exploited successfully.

The Bayesian Network estimates risk using the available vulnerability and access-relationship features. Its output supports security prioritization but does not independently prove that privilege escalation is exploitable.

Attack Behavior :
Non-Privileged Linux User
→
System and Permission Review
→
Vulnerability Identification
→
Access-Relationship Analysis
→
Potential Privilege Escalation Conditions
→
Bayesian Network Risk Estimation
→
Security Finding Validation
→
Linux Access-Control Remediation
→
Post-Remediation Validation

Security Concept

Bayesian Network-Based Privilege Escalation Risk Estimation

The primary security concept is probabilistic risk estimation using a Bayesian Network combined with Linux access-relationship analysis.

In this use case, vulnerability-related information, permission conditions, user privileges, and access relationships are represented as security features. These features are used to estimate privilege escalation risk within the controlled Linux environment.

NetworkX represents relationships between users, groups, processes, services, and system resources as a graph. This helps identify how access relationships may contribute to potential privilege escalation conditions.

Python is used to preprocess the security data and prepare the features required by the Bayesian Network. The resulting risk estimates are reviewed alongside the underlying Linux configuration and assessment evidence.

The assessment follows:
Linux Security Data Collection
→
Vulnerability Feature Extraction
→
Linux Permission Analysis
→
Access-Relationship Graph Creation
→
Bayesian Network Construction
→
Security Evidence Preparation
→
Privilege Escalation Risk Estimation
→
Risk Classification and Review
→
Security Finding Validation
→
Linux Hardening
→
Post-Remediation Validation

Defensive Mechanism

The security concept defines the overall risk-estimation strategy.

The following are the specific defensive mechanisms implemented.

Linux Least-Privilege Access Control :

Linux user permissions and group memberships are reviewed to ensure that accounts receive only the privileges required for their responsibilities.

Purpose: Reduce unnecessary privileges that may contribute to privilege escalation risk.

File and Directory Permission Review

Sensitive files and directories are reviewed to identify inappropriate ownership or permissions.

Purpose
  • Prevent unauthorized users from accessing or modifying protected system resources.

Vulnerability Assessment

Vulnerability information is reviewed to identify software weaknesses that may affect the Linux environment.

Purpose
  • Identify vulnerability-related conditions that may contribute to privilege escalation risk.

Access-Relationship Analysis

Relationships between users, groups, processes, services, and system resources are represented and analyzed.

Purpose
  • Identify risky access relationships that may increase privilege escalation exposure.

Bayesian Network Risk Estimation

A Bayesian Network estimates risk using the selected vulnerability and access-relationship features.

Purpose
  • Support evidence-based prioritization of potentially risky Linux security conditions.

Linux Service Exposure Assessment

Nmap is used to identify network-accessible services and ports on the authorized laboratory target.

Purpose
  • Identify exposed services that require further security review.

Server Security Baseline

OpenSCAP is used to assess the Ubuntu host's security configuration against an appropriate security policy.

Purpose
  • Identify operating-system configuration weaknesses relevant to the assessment.

Security Finding Validation

The model's risk estimates are compared with the observed Linux configuration and assessment evidence.

Purpose
  • Ensure that risk classifications are reviewed against actual security conditions rather than treated as confirmed exploitation.

Risk-Based Prioritization

Validated findings are prioritized according to their severity, accessibility, privilege implications, and potential impact.

Purpose
  • Direct remediation efforts toward the most important security weaknesses.

Post-Remediation Validation

The Linux configuration and relevant security findings are reassessed after remediation.

Purpose
  • Verify that identified security weaknesses have been addressed and that the resulting access controls behave as intended.

Security Tools

Primary Risk Estimation Tool: Python with pgmpy

Python is used to preprocess the security features, while pgmpy provides the Bayesian Network implementation for probabilistic risk estimation.

Purpose
  • Prepare vulnerability and access-relationship features.
  • Construct the Bayesian Network.
  • Represent relevant security variables and dependencies.
  • Estimate privilege escalation risk from available evidence.
  • Support risk classification and assessment reporting.

Access-Relationship Analysis Tool: NetworkX

NetworkX is used to represent and analyze relationships between Linux users, groups, processes, services, and system resources.

Purpose
  • Represent relevant Linux access relationships.
  • Identify connections between users and system resources.
  • Analyze potential paths involving excessive permissions.
  • Prepare relationship-based features for the risk assessment.

Data Processing Tool: Pandas

Pandas is used to load, clean, transform, and organize the security records and features required by the risk-estimation workflow.

Purpose
  • Process publicly available security data.
  • Clean and organize relevant records
  • Prepare vulnerability-related features.
  • Prepare structured input for the Bayesian Network.

Network Service Discovery Tool: Nmap

Nmap is used to identify network-accessible services and ports on the authorized Ubuntu laboratory target.

Purpose
  • Identify running network services.
  • Establish the initial service-exposure baseline
  • Identify services that require additional security review.
  • Support network-exposure validation after remediation.

Server Security Assessment Tool: OpenSCAP

OpenSCAP is used to assess the Ubuntu host's security configuration against an appropriate security policy.

Purpose
  • Assess operating-system security configuration.
  • Identify configuration weaknesses.
  • Review the host against a security baseline.
  • Support post-remediation security validation.

Security Findings and Advisory Tool: Dradis Community Edition

Dradis Community Edition is used to organize and document validated security findings, supporting evidence, risk priorities, and remediation recommendations.

Purpose
  • Record validated security findings.
  • Store technical assessment evidence.
  • Document potential security impact.
  • Track remediation requirements.
  • Prioritize identified risks.
  • Produce structured security-assessment documentation.

Target Platform: Ubuntu Linux

Ubuntu provides the controlled Linux environment used for the privilege escalation risk assessment.

Purpose
  • Host the target operating system.
  • Provide controlled Linux user accounts
  • Support permission and service reviews.
  • Apply required security configuration changes.
  • Support OpenSCAP assessment.

Security Testing Platform: Kali Linux

Kali Linux provides the controlled security-testing environment used to assess the authorized Ubuntu target.

Purpose
  • Perform authorized security testing.
  • Execute Nmap service discovery.
  • Review network-accessible services.
  • Support post-remediation testing.

Virtualization Platform: VirtualBox

VirtualBox provides the isolated laboratory infrastructure for running Ubuntu and Kali Linux virtual machines.

Purpose
  • Host the Ubuntu target system.
  • Host the Kali Linux security-testing system
  • Isolate the security assessment environment.
  • Support controlled testing without intentionally targeting production infrastructure.

Process

STEP 01

Prepare the Isolated Linux Security Environment

  • Create an isolated cybersecurity laboratory using VirtualBox.
  • Configure Ubuntu as the Linux assessment target.
  • Configure Kali Linux as the security-testing system.
  • Establish controlled network communication between the virtual machines.
  • Assign and record the laboratory IP addresses.
  • Verify communication between Kali Linux and Ubuntu.
  • Confirm that all testing is restricted to the authorized laboratory.
Tools: VirtualBox + Ubuntu + Kali Linux
STEP 02

Prepare the Ubuntu Target System

  • Start the Ubuntu virtual machine.
  • Verify that the operating system is functioning correctly.
  • Review the available user accounts and groups.
  • Identify the running system services.
  • Record the initial operating-system configuration.
  • Confirm that the target is ready for the authorized security assessment.
Tools: Ubuntu Linux
STEP 03

Establish the Initial Linux Access Baseline

  • Identify the designated administrative account.
  • Create or identify a controlled non-privileged laboratory account.
  • Review the permissions assigned to the laboratory account.
  • Review the account's group memberships.
  • Identify the resources that the account is authorized to access.
  • Record the initial access-control state.
  • Confirm the intended permissions before beginning the assessment.
Tools: Ubuntu Linux
STEP 04

Collect Vulnerability-Related Security Information

  • Obtain publicly available security data suitable for the selected risk-estimation workflow.
  • Load the available records into the Python environment.
  • Identify the vulnerability-related fields relevant to the assessment.
  • Review the available severity and vulnerability information.
  • Check whether the selected records contain sufficient information for the intended features.
  • Record any missing or incomplete fields.
  • Prepare the relevant information for further processing.
Tools: Python + Pandas
STEP 05

Review Linux Permissions and Access Relationships

  • Review the permissions assigned to the designated laboratory account.
  • Inspect relevant user and group relationships.
  • Review access to selected files and directories.
  • Identify services and processes relevant to the assessment.
  • Review the relationship between the account and accessible system resources.
  • Identify excessive permissions or suspicious access relationships where present.
  • Record the observed access-control conditions.
Tools: Ubuntu Linux
STEP 06

Perform Controlled Vulnerability and Service Assessment

  • Perform authorized service discovery against the Ubuntu laboratory target.
  • Use Nmap to identify network-accessible ports and services.
  • Record the identified services and their accessible ports.
  • Review whether the observed services are expected in the laboratory environment.
  • Identify services that require further security assessment.
  • Correlate the observed service information with the available vulnerability records where relevant.
  • Preserve the initial assessment evidence.
Tools: Nmap + Kali Linux + Ubuntu
STEP 07

Prepare the Security Features

  • Load the selected security records into Pandas.
  • Clean and organize the relevant vulnerability-related information.
  • Select the features required by the risk-estimation model.
  • Prepare the relevant Linux access and permission features from the assessment information.
  • Standardize feature representations where necessary.
  • Check for missing values and inconsistent records.
  • Prepare the structured features for the Bayesian Network workflow.
Tools: Python + Pandas + Ubuntu Linux
STEP 08

Represent Linux Access Relationships as a Graph

  • Identify the relevant users, groups, processes, services, and system resources.
  • Represent the selected entities as graph nodes.
  • Represent the observed access relationships as graph edges.
  • Use NetworkX to construct the access-relationship graph.
  • Review the graph for relevant connections between the laboratory account and system resources.
  • Identify relationships that may require further security review.
  • Record the relationship-based features for the risk-estimation workflow.
Tools: Python + NetworkX + Ubuntu Linux
STEP 09

Define the Bayesian Network Variables

  • Identify the security variables required for the risk-estimation model.
  • Define the relevant vulnerability-related variables.
  • Define the relevant permission and access-relationship variables.
  • Define the risk condition that the model is intended to estimate.
  • Determine the relationships between the selected variables using an appropriate model design.
  • Ensure that the variables and their possible states are clearly defined.
  • Record the model assumptions and limitations.
Tools: Python + pgmpy
STEP 10

Construct the Bayesian Network

  • Implement the Bayesian Network using pgmpy.
  • Define the selected security variables as model nodes.
  • Establish the conditional dependencies between the variables according to the model design.
  • Configure the conditional probability distributions using an appropriate, documented method.
  • Verify that the network structure is valid.
  • Check that the probability distributions are configured correctly.
  • Record the model configuration for the assessment.
Tools: Python + pgmpy
STEP 11

Perform Bayesian Network-Based Risk Estimation

  • Prepare the security evidence required by the Bayesian Network.
  • Provide the relevant vulnerability and access-relationship features to the model.
  • Perform probabilistic inference using the configured network.
  • Obtain the estimated probability associated with the defined privilege escalation risk condition.
  • Apply the predefined risk-classification criteria if risk categories are required.
  • Record the resulting risk estimates.
  • Ensure that the output is treated as a model-based estimate rather than proof of successful exploitation.
Tools: Python + pgmpy + Pandas
STEP 12

Validate and Correlate the Security Findings

  • Review the Bayesian Network risk estimates.
  • Review the underlying vulnerability-related information.
  • Review the Linux permission and group-membership evidence.
  • Review the access-relationship graph.
  • Review the Nmap service-discovery results.
  • Compare the model output with the observed Linux security configuration.
  • Identify findings that require additional investigation.
  • Confirm which findings are supported by the available assessment evidence.
Tools: Python + pgmpy + NetworkX + Nmap + Ubuntu Linux
STEP 13

Document the Security Findings

  • Create the security assessment project in Dradis Community Edition.
  • Record the Ubuntu Linux system as the assessed asset.
  • Document the identified vulnerability and access-control findings.
  • Record the relevant Linux permissions and access relationships.
  • Document the Bayesian Network risk estimates.
  • Add supporting evidence from the authorized security assessment.
  • Document the potential security impact and model limitations.
  • Record the recommended remediation actions.
Tools: Dradis Community Edition + Python + Ubuntu Linux
STEP 14

Perform Risk-Based Prioritization

  • Review the validated Linux security findings.
  • Evaluate the severity of the relevant vulnerability information.
  • Review the privileges associated with the affected account or resource.
  • Consider the accessibility of the affected service or resource.
  • Review the Bayesian Network risk estimates alongside the technical evidence.
  • Consider the potential impact on system resources and sensitive data.
  • Determine the remediation priority using documented risk criteria.
  • Record the risk-prioritization decision in Dradis.
Tools: Dradis Community Edition + Python + pgmpy
STEP 15

Develop and Apply the Linux Remediation Strategy

  • Review the prioritized security findings.
  • Identify unnecessary administrative privileges.
  • Remove inappropriate permissions or group memberships where confirmed.
  • Correct insecure file and directory permissions where necessary.
  • Review affected services and their configurations.
  • Apply the appropriate security configuration changes.
  • Preserve legitimate system functionality while enforcing least privilege
  • Record the remediation actions performed.
Tools: Ubuntu Linux + Dradis Community Edition
STEP 16

Perform Post-Remediation Security Testing

  • Review the Linux access controls after remediation.
  • Recheck the permissions of the designated non-privileged laboratory account.
  • Verify that the account cannot access resources beyond its authorized permissions.
  • Repeat the relevant Nmap service-discovery assessment.
  • Compare the observed service exposure with the initial assessment
  • Reassess the relevant security features after configuration changes.
  • Record the post-remediation evidence.
Tools: Ubuntu Linux + Nmap + Kali Linux + Python
STEP 17

Reassess Privilege Escalation Risk

  • Update the relevant security features using the post-remediation assessment evidence.
  • Provide the updated features to the configured Bayesian Network.
  • Perform risk estimation again using the same documented model assumptions.
  • Compare the initial and post-remediation risk estimates.
  • Review whether the risk classification has changed.
  • Confirm that any reduction in estimated risk is supported by the observed configuration changes.
  • Record any remaining security weaknesses that require further action.
Tools: Python + Pandas + pgmpy + NetworkX
STEP 18

Perform Final Security Validation and Advisory Review

  • Execute the appropriate OpenSCAP security configuration assessment.
  • Compare the initial and final security-baseline results.
  • Review the original Linux access-control and vulnerability findings.
  • Review the implemented remediation actions.
  • Compare the pre-remediation and post-remediation security evidence.
  • Review the Bayesian Network risk estimates and their supporting features.
  • Update the findings in Dradis Community Edition.
  • Mark successfully remediated findings.
  • Record residual risks and any limitations in the assessment.
  • Finalize the Linux privilege escalation risk assessment and security recommendations.
Tools: OpenSCAP + Dradis Community Edition + Python + pgmpy + NetworkX + Nmap

Outcome

An isolated Ubuntu Linux assessment environment is successfully established using VirtualBox, with Kali Linux providing the authorized security-testing environment.

The Linux user accounts, group memberships, file permissions, services, and relevant access relationships are reviewed to establish the initial access-control state.

Vulnerability-related security information is processed using Python and Pandas, producing structured features for the privilege escalation risk-estimation workflow.

NetworkX is used to represent relevant relationships between users, groups, processes, services, and system resources, helping identify access relationships that require further investigation.

A Bayesian Network is constructed using pgmpy to estimate privilege escalation risk from the selected vulnerability and access-relationship features.

The estimated risk is reviewed alongside Linux configuration evidence, vulnerability information, and service-discovery results to support security finding validation and risk prioritization.

Validated findings, risk estimates, technical evidence, and remediation recommendations are documented using Dradis Community Edition.

Linux security weaknesses are addressed through appropriate permission corrections, removal of unnecessary privileges, and relevant configuration hardening, reducing identified privilege escalation risk factors.

Post-remediation testing and reassessment compare the initial and final security conditions, helping verify whether the identified weaknesses have been addressed while legitimate Linux operations remain functional.

The complete Bayesian Network-based privilege escalation risk-estimation workflow, vulnerability feature processing, access-relationship analysis, security finding validation, risk prioritization, Linux hardening, and post-remediation validation is demonstrated in the controlled laboratory environment.