[CentOS] Find reason for heavy load

Noob Centos Admin centos.admin at gmail.com
Thu Dec 31 18:41:46 UTC 2009


Hi,

> I do not know about now but I had to unload the modules in question.
> Just clearing the rules was not enough to ensure that the netfilter
> connection tracking modules were not using any cpu at all.

Thanks for pointing this out. Being a noob admin as my pseudonym
states, I'd assumed stopping apf and restarting iptables was
sufficient. I'll have to look up unloading module later.

> /me shrugs. When I was the mta admin at Outblaze Ltd. (messaging
> business now owned by IBM and called Lotus Live) spammers always ensured
> I got called. All they do is just press the big red button (aka start
> the script/system) and then go and play while I would have to deal with
> whatever was started.

Based on the almost precise timing of around 9:30 to 5:30 India time,
I'm inclined to think in my case it wasn't so much a spammer pressing
a red button but a compromised machine in an office starting up when
the user gets into office and knocks off on time at 5:30 :D

> I remember only one occasion when the spams were
> launched but neutralized very soon because they were pushing a website
> and I found a sample real early and so the anti spam system could just
> dump the spams and knock out accounts being used to send the crap.

Could I ask how do I knock out the accounts sending the crap if they
are not within my systems?

> First, try rmmod'ing the netfilter modules after you have cleared away
> the state related rules to make sure that you are only using static
> rules in netfilter...unless you have done that already..

I think I'm only using static rules because after I restart iptables,
I would then do a service iptables status to check my rules were in,
and that list was very short compared to when APF was active.

The good news is, I think I've fixed the big problem after doing my
shutdown tests and returned to the original problem.


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