Why is my server using so much memory?

I haven't even set up my website on my dedicated server so I'm the only one using it at the moment. And yet this is what I see in my sys info:

Full Size

I just got a bunch of security softwares installed today so I'm wondering if that could be the reason. Programs like Dos deflate, CSF firewall, Mod_security, SIM, Log watch, etc.

My server's details:

CentOS  
Processor       Intel Xeon CPU X3220  
CPU Speed       2.39 GHz  
Cache Size      4.00 MB  
RAM             2GB DDR2

Your picture shows 56% cached memory. Linux works with kernel and cache loaded in the RAM to speed up things. When you have more applications taking up memory, the cache will be reduced to trade off its advantages for running more apps.

In short, things are fine; you are not running out of memory.
The Kernel+Apps memory utilization is near the 30% mark.

Update: sebthebert gave this nice link to LinuxAteMyRam for more reading on the subject.

It's using 600MB of memory at the moment - you must have quite a few things running, but it's not unreasonable.

Ignore the 'buffers' and 'cached' lines - those are disk buffers and disk cache. The system's just using that because it's there.

Look at the 'Kernel + Applications' line to see what the programs are actually using.

There's nothing wron with that picture. My server with 768M RAM routinely sits at or near 100% utilization - even when the load averages are 0.01 0.01 0.01 and the busiest process is top.

If, after running your server with its "real" load, it's running out of memory, that's when you start worrying :)