Dos attack? / Server loads shooting up? / what to do? / where to get help?

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We have a 16,000 member forum

Nearly 3 million page views per month

max users online approx 600

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I guess folks search a lot..

Our loads are shooting up to 100+ etc every 15 mins or so. We have been manually restarting Apache in root. Past load level 5 or 6 and the forum freezes.. Its becoming a serious PITA.

I am not the web tech.. the data below was taken during an OK period.

We dont have - load balancing or a hardware firewall..

We CAN NOT asertain if this is a tech issue or a malicious attack and our server company cant figure it out either....

Any threads / links / tips - that I can show my web tech would be VERY appreciated!

Thanks in advance,

MM

Server Load Averages 1.69 1.57 4.35 | 313 Users Online (173 members and 140 guests)

Admin Control Panel
Server Type Linux Data Usage 650.02 MB Users to Moderate 2 [View]
Web Server Apache v1.3.34 Index Usage 284.39 MB Threads to Moderate 0 [View]
PHP 5.1.2 Attachment Usage 9.61 GB Posts to Moderate 0 [View]
PHP Max Post Size 55.00 MB Avatar Usage 11.67 MB Attachments to Moderate 0 [View]
PHP Maximum Upload Size 8.00 MB Profile Picture Usage 13.5 KB Events to Moderate 0 [View]
PHP Memory Limit None Unique Members Today 1,523 New Threads Today 38
MySQL Version 4.1.13-standard New Users Today 10 New Posts Today 507
MySQL Packet Size 1,024.00 MB