Audit log - definition & overview

An audit log, often called an audit trail or audit history, is a chronological record of events, actions and changes within a computer system, software application, network or organization. The primary purpose of an audit log is to maintain a detailed and tamper-evident record of activities and transactions for accountability, security, compliance and troubleshooting.

Accountability and transparency: Audit logs help establish a clear trail of user activity administrators and systems. These historical records document the evolution of a system or organization over time and can be valuable for future reference, analysis and decision-making. This record deters unauthorized or malicious actions, as individuals know their actions are being recorded and can be traced back to them.

Compliance and regulations: Many regulations and standards (such as HIPAA, PCI DSS and GDPR) require organizations to maintain audit logs as part of their data protection and security practices. Audit logs provide evidence of compliance with these regulations, facilitating a security audit and inspections by regulatory authorities.

Forensic analysis: In the event of a security incident, audit logs serve as valuable sources of information for forensic analysis. Security professionals can use the audit trail to reconstruct events leading up to and following an incident, aiding in the investigation and identification of the attack vector.

Legal and dispute resolution: In legal proceedings or disputes, audit logs can provide verifiable evidence of actions taken, transactions performed and interactions within a system. This evidence can help resolve disputes and protect organizations from false claims.

Security monitoring: By capturing and logging events such as login attempts, access to sensitive data and system modifications, audit logs enable real-time monitoring of security-related activities. Suspicious or unauthorized behavior can be detected and responded to promptly, enhancing overall system security.

Incident detection and response: Audit logs are essential for identifying and responding to security breaches, data breaches and other unauthorized activities. When unusual patterns or anomalies are detected in the audit trail, security teams can investigate and take appropriate action to mitigate potential threats.

Troubleshooting and diagnostics: Audit logs aid in diagnosing and resolving technical issues by providing insights into system behavior, errors and performance bottlenecks. IT teams can analyze logs to pinpoint the causes of system failures or anomalies and implement appropriate fixes.

Change management: Audit logs track configuration changes and system modifications, helping organizations maintain control over their IT environments. Changes can be reviewed to ensure they were authorized and to identify potential causes of disruptions.

Performance analysis: By analyzing audit logs, organizations can gain insights into system usage, resource consumption and user behavior. This information can be used to optimize system performance and resource allocation.

Both system logs and audit logs play important roles in monitoring and maintaining the security of computer systems, networks and applications. However, they serve distinct purposes and capture different types of information. System logs provide a broad view of system operations and performance, while audit logs focus on recording security-related events to ensure compliance, monitor security incidents and facilitate forensic analysis. Both logs are essential for maintaining computer systems and networks' overall health and security. Here's the difference between a system log and an audit log:

Common types of information captured in system logs include:

• System status: Information about the system's state, including startup, shutdown and restart events.

• Error messages: Notifications about errors, warnings and exceptions encountered by the system, applications, or hardware components.

• Resource usage: Data for utilizing system resources such as CPU, memory, disk space and network bandwidth.

• Software and hardware events: Information about software installations, updates, hardware changes and device connections.

• Service status: Details about the availability and performance of network services and daemons.

• Authentication and authorization: Records of user logins, logouts and access control events.

Securing audit logs is crucial to maintaining the integrity, confidentiality and availability of the recorded data. Properly secured audit logs help prevent unauthorized access, tampering and manipulation of critical event records. Here are several practices and strategies to enhance the security of audit logs:

Access control
Limit access to audit logs to authorized personnel only with role-based access controls. Strong authentication mechanisms, such as multi-factor authentication (MFA), can ensure that only authorized users can access audit log data.

Encryption
Encrypt audit log data both in transit and at rest to protect against interception and unauthorized access. Also, use encryption protocols and algorithms that are robust and compliant with industry standards.

Tamper-evident design
Implement measures to ensure the integrity of audit logs, making it difficult for unauthorized parties to tamper with or modify the records. Use cryptographic hash functions or digital signatures to create a tamper-evident seal for each log entry.

Centralized logging
Implement centralized logging solutions to collect and store audit logs in a dedicated and secure location, like a security data lake. Centralized logs are easier to monitor, analyze and protect than logs dispersed across various systems.

Redundancy and backup
Maintain redundant copies of audit logs in secure locations to prevent data loss due to hardware failures, disasters or cyberattacks. You’ll also want to regularly back up audit logs and test the restoration process to ensure recoverability.

Secure storage and retention
Store audit logs on secure and hardened storage systems with appropriate role-based access controls. You’ll need to define and adhere to retention policies that specify how long logs should be retained to meet regulatory and compliance requirements.

Monitoring and alerts
Implement real-time monitoring of audit logs for suspicious activities, anomalies or unauthorized access attempts. And be sure to configure alerts and notifications to notify security teams of potential security breaches.

Regular review and analysis
Regularly review and analyze audit logs to detect patterns, anomalies, or unauthorized activities. Conducting periodic audits and reviews can ensure that logs are accurate and complete.

Immutable logging
Use techniques that make audit logs immutable, i.e. tamper-resistant, such as write-once storage or append-only logs, to prevent unauthorized modifications.

Secure backup and archiving
When backing up or archiving audit logs, ensure the backup copies are as secure as the original logs. Apply encryption and access controls to backup data.

Secure logging infrastructure
Ensure the infrastructure and systems responsible for generating, collecting and transmitting audit logs are secure and protected against attacks targeting the logging infrastructure, such as log injection attacks.

Vendor and third-party security
If using third-party logging solutions, assess their security practices, data handling and encryption mechanisms to ensure they meet your security requirements and compliance regulations.

Documentation and policies
Document security procedures and policies for managing and securing audit logs and use them to train personnel involved in managing and accessing them to ensure proper handling and security awareness.

Securing audit logs is a multi-layered effort that involves technical controls, best practices and ongoing vigilance. By implementing these measures, organizations can safeguard their audit log data and maintain the trustworthiness of their security and compliance efforts.

The availability of an auditing record after an event depends on several factors, including the design and configuration of the auditing system, the type of event being recorded and the specific policies and requirements of the organization. Some auditing systems are designed to provide real-time event logging, meaning that audit records are generated and made available almost immediately after an event. Other systems might use batch processing, where audit logs are collected and processed at specific intervals, resulting in a slight delay between the event and the availability of the corresponding audit record.

In many cases, organizations strive to strike a balance between real-time logging and system performance considerations. They design their auditing systems to capture critical events promptly while managing the potential impact on system resources. The time it takes for an auditing record to be available can vary widely and should be determined based on the organization's specific needs, security goals and technical capabilities.

Organizations often follow a combination of scheduled and event-triggered audit log reviews. For example, regularly scheduled reviews could occur daily, weekly, monthly or quarterly, depending on the organization's needs or as specified by compliance regulations. These reviews help ensure ongoing monitoring and regulatory compliance. In contrast, event-triggered reviews might be triggered by specific events, such as system updates, security incidents or changes in the threat landscape. After such events, more frequent reviews might be necessary to assess the impact.

The frequency of reviewing audit logs depends on several factors. There is no one-size-fits-all answer, but here are some considerations to help determine how often audit logs should be reviewed:

• Some industries and compliance regulations specify the frequency of audit log reviews. Ensure that your review schedule aligns with these requirements.

• The level of risk associated with the systems and processes being monitored. High-risk systems might require more frequent and rigorous log reviews.

• Systems with high event volumes or critical functions might warrant more frequent reviews to ensure timely detection of anomalies or security incidents.

• Consider the operational impact of log reviews. Frequent reviews might be necessary during periods of heightened activity, such as system updates or major events.

• During and after a security incident, logs may need to be reviewed more frequently to identify the scope and impact of the incident.

• If you have automated tools or systems to analyze log events and trigger alerts for suspicious activities, the frequency of manual reviews might be adjusted accordingly.

• Your organization’s size will often determine the resources available. Larger organizations might have dedicated teams or tools for log analysis, allowing for more frequent reviews.

Sumo Logic is a cloud-native, secure, centralized log analytics service that provides insights into logs through pre-built applications, identifying patterns to show outliers in the behaviors of applications and systems. Security teams and compliance analysts can then instantly act on these outliers, get to the root cause and prevent any future impact on the business.

Sumo Logic can collect logs from almost any system in nearly any format, and our centralized log management service analyzes over 1.5 exabytes of data per day. Learn more about log management in our guide.

Sumo Logic provides everything you need to conduct real-time forensics and log management for your IT data without performing complex installations or upgrades or needing to manage and scale any hardware or storage. With fully elastic scalability, Sumo Logic is fit for any size deployment.

The Sumo Logic Audit app uses Sumo Logic audit index events to present information about account management activities, user activities and management of library content searches, dashboards, reports and folders in your Sumo Logic account. The app uses predefined searches and dashboards that provide visibility into your environment.

Learn more about Sumo Logic's log analytics solution.