Maintenance, Monitoring, and Analysis of Audit Logs
Collect, manage, and analyze audit logs of events that could help detect, understand, or recover from an attack.
Why Is This Control Critical?
Deficiencies in security logging and analysis allow attackers to hide their location, malicious software, and activities on victim machines. Even if the victims know that their systems have been compromised, without protected and complete logging records they are blind to the details of the attack and to subsequent actions taken by the attackers. Without solid audit logs, an attack may go unnoticed indefinitely and the particular damages done may be irreversible.
Sometimes logging records are the only evidence of a successful attack. Many organizations keep audit records for compliance purposes, but attackers rely on the fact that such organizations rarely look at the audit logs, so they do not know that their systems have been compromised. Because of poor or nonexistent log analysis processes, attackers sometimes control victim machines for months or years without anyone in the target organization knowing, even though the evidence of the attack has been recorded in unexamined log files.
How to Implement This Control
|CSC 14-1||Include at least two synchronized time sources (i.e., Network Time Protocol - NTP) from which all servers and network equipment retrieve time information on a regular basis so that timestamps in logs are consistent, and are set to UTC (Coordinate Universal Time).||Quick win|
|CSC 14-2||Validate audit log settings for each hardware device and the software installed on it, ensuring that logs include a date, timestamp, source addresses, destination addresses, and various other useful elements of each packet and/or transaction. Systems should record logs in a standardized format such as syslog entries or those outlined by the Common Event Expression initiative. If systems cannot generate logs in a standardized format, log normalization tools can be deployed to convert logs into such a format.||Quick win|
|CSC 14-3||Ensure that all systems that store logs have adequate storage space for the logs generated on a regular basis, so that log files will not fill up between log rotation intervals. The logs must be archived and digitally signed on a periodic basis.||Quick win|
|CSC 14-4||Develop a log retention policy to make sure that the logs are kept for a sufficient period of time. Organizations are often compromised for several months without detection. The logs must be kept for a longer period of time than it takes an organization to detect an attack so they can accurately determine what occurred.||Quick win|
|CSC 14-5||Have security personnel and/or system administrators run biweekly reports that identify anomalies in logs. They should then actively review the anomalies, documenting their findings.||Quick win|
|CSC 14-6||Configure network boundary devices, including firewalls, network-based IPS, and inbound and outbound proxies, to verbosely log all traffic (both allowed and blocked) arriving at the device.||Visibility/Attribution|
|CSC 14-7||For all servers, ensure that logs are written to write-only devices or to dedicated logging servers running on separate machines from the hosts generating the event logs, lowering the chance that an attacker can manipulate logs stored locally on compromised machines.||Visibility/Attribution|
|CSC 14-8||Deploy a SIEM (Security Incident and Event Management) or log analytic tools for log aggregation and consolidation from multiple machines and for log correlation and analysis. Using the SIEM tool, system administrators and security personnel should devise profiles of common events from given systems so that they can tune detection to focus on unusual activity, avoid false positives, more rapidly identify anomalies, and prevent overwhelming analysts with insignificant alerts.||Visibility/Attribution|
|CSC 14-9||Monitor for service creation events and enable process tracking logs. On Windows systems, many attackers use PsExec functionality to spread from system to system. Creation of a service is an unusual event and should be monitored closely. Process tracking is valuable for incident handling.||Advanced|
|CSC 14-10 (NEW)||Ensure that the log collection system does not lose events during peak activity, and that the system detects and alerts if event loss occurs (such as when volume exceeds the capacity of a log collection system). This includes ensuring that the log collection system can accommodate intermittent or restricted-bandwidth connectivity through the use of handshaking / flow control.||Advanced|
CSC 14 Procedures and Tools
Most free and commercial operating systems, network services, and firewall technologies offer logging capabilities. Such logging should be activated, with logs sent to centralized logging servers. Firewalls, proxies, and remote access systems (VPN, dial-up, etc.) should all be configured for verbose logging, storing all the information available for logging in the event a follow-up investigation is required. Furthermore, operating systems, especially those of servers, should be configured to create access control logs when a user attempts to access resources without the appropriate privileges. To evaluate whether such logging is in place, an organization should periodically scan through its logs and compare them with the asset inventory assembled as part of Critical Control 1 in order to ensure that each managed item actively connected to the network is periodically generating logs.
Analytical programs such as SIM/SEM solutions for reviewing logs can provide value, but the capabilities employed to analyze audit logs are quite extensive, even including, importantly, just a cursory examination by a person. Actual correlation tools can make audit logs far more useful for subsequent manual inspection. Such tools can be quite helpful in identifying subtle attacks. However, these tools are neither a panacea nor a replacement for skilled information security personnel and system administrators. Even with automated log analysis tools, human expertise and intuition are often required to identify and understand attacks.
CSC 14 Effectiveness Metrics
In order to test the effectiveness of the automated implementation of this control, organizations should measure the following:
1. Does each system log appropriately to a central log management system (yes or no)?
2. Does each log event generated include a date, timestamp, source address, destination address and other details about the packet (yes or no)?
3. If a system fails to log properly, how long does it take for an alert about the failure to be sent (time in minutes)?
4. If a system fails to log properly, how long does it take for enterprise personnel to receive the alert about the failure (time in minutes)?
CSC 14 Automation Metrics
In order to automate the collection of relevant data from these systems, organizations should gather the following information with automated technical sensors:
1. What percentage of the organization's systems do not currently have comprehensive logging enabled in accordance with the organization's standard (by business unit)?
2. What percentage of the organization's systems are not currently configured to centralize their logs to a central log management system (by business unit)?
3. How many anomalies / events of interest have been discovered in the organization's logs recently (by business unit)?
CSC 14 Effectiveness Test
To evaluate the implementation of Control 14 on a periodic basis, an evaluation team must review the security logs of various network devices, servers, and hosts. At a minimum the following devices must be tested: two routers, two firewalls, two switches, 10 servers, and 10 client systems. The testing team should use traffic-generating tools to send packets through the systems under analysis to verify that the traffic is logged. This analysis is done by creating controlled, benign events and determining if the information is properly recorded in the logs with key information, including a date, timestamp, source address, destination address, and other details about the packet. The evaluation team must verify that the system generates audit logs and, if not, an alert or e-mail notice regarding the failed logging must be sent within 24 hours. It is important that the team verify that all activity has been detected. The evaluation team must verify that the system provides details of the location of each machine, including information about the asset owner.
CSC 14 System Entity Relationship Diagram
Organizations will find that by diagramming the entities necessary to fully meet the goals defined in this control, it will be easier to identify how to implement them, test the controls, and identify where potential failures in the system might occur.
A control system is a device or set of devices used to manage, command, direct, or regulate the behavior of other devices or systems. In this case, we are examining audit logs, the central log database system, the central time system, and log analysts. The following list of the steps in the above diagram shows how the entities work together to meet the business goal defined in this control. The list also delineates each of the process steps in order to help identify potential failure points in the overall control.
Step 1: Production systems generate logs and send them to a centrally managed log database system
Step 2: Production systems and log database system pulls synchronize time with central time management systems
Step 3: Logs analyzed by a log analysis system
Step 4: Log analysts examine data generated by log analysis system.
Critical Security Controls - Version 5
- 1: Inventory of Authorized and Unauthorized Devices
- 2: Inventory of Authorized and Unauthorized Software
- 3: Secure Configurations for Hardware and Software on Mobile Devices, Laptops, Workstations, and Servers
- 4: Continuous Vulnerability Assessment and Remediation
- 5: Malware Defenses
- 6: Application Software Security
- 7: Wireless Access Control
- 8: Data Recovery Capability
- 9: Security Skills Assessment and Appropriate Training to Fill Gaps
- 10: Secure Configurations for Network Devices such as Firewalls, Routers, and Switches
- 11: Limitation and Control of Network Ports, Protocols, and Services
- 12: Controlled Use of Administrative Privileges
- 13: Boundary Defense
- 14: Maintenance, Monitoring, and Analysis of Audit Logs
- 15: Controlled Access Based on the Need to Know
- 16: Account Monitoring and Control
- 17: Data Protection
- 18: Incident Response and Management
- 19: Secure Network Engineering
- 20: Penetration Tests and Red Team Exercises
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