Logging is one of the most important aspects of any security program. It provides a record of events that occur within your environment, which allows you to understand how your systems are being used and what vulnerabilities exist. Logging helps you identify issues before they become problems, and it gives you insight into what happened after the fact.
There are many different types of logs, each with its own purpose. Some logs are designed to provide information about system activity, while others are intended to capture information about network traffic or application behavior. There are also different levels of logging, ranging from basic records of actions taken by applications, to detailed records of every event that occurs during the execution of an application.
In general, the more detail you can include in your logs, the better. For instance, if you’re looking for evidence of a compromise, you’ll need to look for signs of unauthorized access to your systems. A log entry that includes details about the IP addresses involved in the request will allow you to correlate the requests with the users making them. Similarly, if you’re trying to determine whether a particular file was accessed by someone else, you’ll need to examine the contents of the log entries associated with that file.
As you consider what type of logs to create, keep in mind that not all logs are created equal. In addition, not all logs are equally useful. For example, a log of HTTP requests might be helpful in determining whether a web server has been compromised, but it won’t tell you much about the nature of the threat. On the other hand, a log of failed login attempts could indicate that a malicious actor is attempting to gain access to your systems.
The best way to decide what kind of logs to create is to think about the specific threats you face and the kinds of information you want to collect. If you’re concerned about a particular type of threat, such as phishing emails, then you’ll probably want to track email messages sent to your domain. If you’re worried about malware infections, you’ll likely want to monitor the activities of your users’ computers.
In general, as a minimum, make sure the elements of the common logging format are included and build from there. If you need assistance with log design or help determining and implementing a logging strategy, drop us a line at firstname.lastname@example.org. We’re happy to help!