Log Analysis (or log inspection) is done inside OSSEC by the logcollector and analysisd processes. The first one collects the events and the second one analyzes (decodes, filters and classifies) them.
It is done in real time, so as soon as an event is written OSSEC will process them. OSSEC can read events from internal log files, from the Windows event log and also receive them directly via remote syslog.
Inside OSSEC we call log analysis a LIDS, or log-based intrusion detection. The goal is to detect attacks, misuse or system errors using the logs.
LIDS - Log-based intrusion detection or security log analysis are the processes or techniques used to detect attacks on a specific network, system or application using logs as the primary source of information. It is also very useful to detect software misuse, policy violations and other forms of inappropriate activities.
How often are logs monitored?
In real time.
Where are the events analyzed?
In the manager.
How long are they stored?
For as long as your policy dictates (it is user configurable).
Where does this help me with compliance?
(PCI DSS, etc) It helps with the whole section 10 (log monitoring) of PCI.
How much CPU does it use?
On the agent, it uses very little CPU/memory since it just read the events and forwards them to the manager.
On the manager, it depends on the number of events per second (EPS).
How does it deal with false positives?
False positives can be eliminated using local rules.
These options should be specified locally in each agent’s ossec.conf file or the
share agent.conf. Inside the
<localfile> element, you can have the following
With in OSSEC there are two major methods for monitoring logs: file and process. Each method has its own page and examples.