Log Source Verification
A critical function of any SIEM environment is verifying that the intended systems are logging successfully. Systems that are believed to be logging to a SIEM that aren’t pose a significant risk to an organization, creating a false sense of security and limiting the amount of data available for an investigation.
A common mistake that can be made while verifying if a particular system is logging to a SIEM is using the incorrect fields for confirmation. For example, most SIEMs have several IP address and hostname fields, ranging from source IP address, destination IP address, device IP address, and others. Given the multiple fields, it can be confusing to know which is used for what, especially for new staff. This leaves a possibility that staff are pulling incorrect data and providing inaccurate results when performing verification or searching in general.
As an example, Company A is implementing a new Linux server, and the SOC is being asked if they can see logs coming from it, 172.16.2.1. The SIEM application has three IP address fields: Device IP Address, Source IP Address, and Destination IP Address. The Device IP Address field contains the IP address of the server generating the log event. The Source IP Address is the source of the event, and the Destination IP Address field is the target of the event.
One of the SOC analysts performs the verification, searches for “172.16.2.1,” and gets one result:
Event Name: Accept
Source IP Address: 10.1.1.1
Source Port: 22
Device IP Address: 172.16.50.25
Destination IP Address: 172.16.2.1
Destination Port: 22
Without paying attention to the field names, the analyst mistakenly mentions that the new Linux server is logging, when in fact what he’s looking at is an accept traffic event generated from firewall 172.16.50.25, not an event from the new server. The project to implement the new server is now considered completed, and Company A now has a security gap.
While this can be a major issue and add risk to an organization, a simple process can be followed to show staff which fields to use for verification. Your SIEM vendor can also easily tell you which fields to use as well. Learning and education sessions on searching can also be used to address this and ensure staff know how to search effectively.