SIEM

• Centralize events - if everything is in one place it's much easier to search for something.
• Normalize events - if the format of the events is the same we can actually search for things.
• Search events - perhaps everything for a period of time or for an IP address or username.
• Report on events - provide executive summaries on security and fault issues on a regular basis.
• Correlate events - configure some logic so that if certain events happen within a specified period of time an alert of some sort can be generated.

 

 

The following factors will make sure your SIM project is a success;

 

1. Events Per Second (EPS) - This is the rate at which your networked devices will be sending events to the SIM.  If this number is not calculated correctly the first thing that will happen is that the SIM will start to drop events before they are stored in the database.  Think about a back catcher trying to catch 10 balls at the same time.  If you are dropping events before they are able to get used by the SIM your searches, reporting, and correlation will all be incorrect and misleading. Again most SIM manufacturers will be able to help determine this number by the number of and types of networked devices you have, and the number of users.
2. Storage - If the SIM is not sized correctly you won't be able to keep the anticipated number of events for the desired amount of time.  It's like filling a gas tank.  If the tank is already full you need to burn off (or delete) the gas before you put more in.  The issue is that if you want to be able to look back three months for forensic or compliance requirements you may no longer be able to.  Know how long you want to be able to go back on the fly during the sizing phase.  Three months is pretty standard.
3. Parsing - A key feature of log management is to normalize events to put all data in the right fields so that it can be queried. For example a Cisco firewall may have the time in a different format than a network intrusion prevention system. In order to search all events for that specific time they must all look the same, otherwise referred to as normalized or parsed. If the SIM doesn't support all of your critical systems and applications out of the box it's not the end of the world. What it does mean is that you are going to have to write some parsing rules. It is not extremely difficult but can be challenging and is definitely time consuming.  Compare the list of device types you plan on getting events from to the list of event sources supported by the manufacturer.
4. Filtering - Because EPS ratios and storage are somewhat precious resources in SIMs there may be certain events from an event source that you don't want to store in the database.  The issue is that some network elements can send either all events or no events to a SIM.  For example your Network IPS may have an informational signature for detecting DNS traffic.  The only thing you may be using it for is monitoring for volume changes in DNS so storing these billions of events in the SIM may not be desired.  Ask the SIM manufacturer about the possibility of filtering events before they get into the database.  In some cases the databases are so efficient that it will not matter.  Keep in mind the more you send to SIM the more useful it is, and the more costly it is.
5. Management - SIM architecture is very similar to other servers. You have the hardware, an operating system, a database, and the application. To manage each of these components separately is very cumbersome. It sounds like a normal day at the office but when you consider that some of the best SIMs come as an appliance, why would you waste your time with having to manage each component separately? There is enough to do with a SIM that you don't want to spend months preparing for an upgrade.  Look for SIMs that you can easily download and run a file to upgrade the system like you would a router or switch.
6. Accountability - who is responsible for managing the system to keep it alive and all the hardware and software up to date? Falling behind with security updates is more like eating stale dairy than stale bread. Making it easy to manage is key and assigning a single team to be in charge of updating the system and it's content is important. The other responsibility is managing events. I prefer open systems within the organization. The security team may oversee the system and help develop content like correlation rules and filters, but the network, Linux  windows, database, and application administers should have access too. They know their systems better than anyone and if they are willing to contribute correlation rule use cases the SIM will only get better. They may even want to be the ones to monitor their custom correlation rules.  This will help reduce mean time to resolution of incidents, which is the entire point of the solution
7. https://community.mcafee.com/community/business/siem/blog/tags/correlation
8. http://blogs.gartner.com/anton-chuvakin/2013/09/24/detailed-siem-use-case-example/