I have dedicated server with ovh and it seems server is not secure. My server is down 2-3 times a day. It may be because of DDOS or some virus attack. I need help of experienced server administrator, who can resolve this issue ASAP.
Can you give more details on what the server is running (like OS, Apache/IIS?, 3rd party scripts/apps?) Do you notice that it goes down at random intervals or is it a consistent pattern?
Have you reported the problem to them ? Doesn't the server have a firewall installed? I'd recommend you to try scanning the server for any infections. If you assume it to be a victim of DDoS, I'd recommend you to purposely take down the server for some time and raise this issue with your host on top priority. They'd be able to assist you better in this case as there might be other machines over the ip subnet that would've possibly be facing the same issue.
I think before anyone goes any further, it's important to define what the OP means by "down". That's far too vague to even begin making an analysis. Is the whole server unavailable? Can he connect via remote connections? Is there a KVM system attached - is the server available via that? Does the server just stop serving some sites or all of them. Is it a particular language that isn't responding - static HTML sites? php sites? asp.net site? How, if the server is truly "down" (I mean off), does it come alive again? Is it really down or just unresponsive? What does unresponsive mean? What do traffic logs show? If it's a dedicated server I assume the host is providing MRTG stats (they should be) - what do they show when your server is "down"? If it's excess traffic it may be a DOS attack but it would have to be a lot of traffic? You need to find out a lot more about what is going on. Saying it is "down" is no help and no use to anyone. You need to be much more specific. Finally, it goes without saying, if you're not an experienced server admin then you shouldn't have a dedicated server. Pay the host to manage it or you'll never get it working reliably and securely. Having server attached to a hostile internet 24/7 is not like running a PC in the confines of your relatively safe home environment. Dedicated servers take time to set-up and secure properly and just as much time to maintain and keep them safe. Get someone experienced to look after it. Not just to solve this problem, but ALL THE TIME.