HELP! email security breeched! :(
I get hundreds of thosands of spam below! can anyone guide me how to buff up the security of my cPanel Linux server? To stop spams and enhance security?Can I stop the spams like below simply by enabling SMTP Tweak in cPanel? Anything else I can do or install to protect my server?

"> 83.149.123.0/24 routing block because of spam-trap mail
>
>
>
> and unresolved abuse complaints for
>
> 83.149.123
> 83.149.210
> 83.149.69
> 83.149.90
>
>
> Return-Path: <ldobbs@beststrength.com>
> Received: from webserver.apc.sg ([83.149.123.53]) by
> zoon.lafn.org
> (8.13.1/8.11.3) with ESMTP id jBKBlJlj010069 for <SPAM-TRAP@lafn.org>;
> Tue, 20 Dec 2005 03:47:26 -0800 (PST) (envelope-from
> ldobbs@beststrength.com)
> Received: from mx1.genutrust.com ([4.79.248.64]
> helo=rigshow.com) by
> webserver.apc.sg with esmtpa (Exim 4.52) id 1EofxG-0002FM-20 for
> SPAM-TRAP@lafn.org; Tue, 20 Dec 2005 12:46:54 +0100
> Message-ID: <20051220064640.6C92AF877A002D9D@beststrength.com>
> From: Laura Dobbs <ldobbs@beststrength.com>
> To: SPAM-TRAP <SPAM-TRAP@lafn.org>
> Subject: Just needs your approval
> Reply-To: ldobbs@beststrength.com
> Date: 20 Dec 2005 06:46:40 -0500
> MIME-Version: 1.0
> Content-Type: multipart/alternative;
> boundary="----=_NextPart_000_0012_7E1EC209.5A588755"
> X-AntiAbuse: This header was added to track abuse, please include
> it
> with any abuse report
> X-AntiAbuse: Primary Hostname - webserver.apc.sg
> X-AntiAbuse: Original Domain - lafn.org
> X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [47 12]
> X-AntiAbuse: Sender Address Domain - beststrength.com
> X-Source:
> X-Source-Args:
> X-Source-Dir:
> X-Virus-Scanned: ClamAV 0.86.2/1213/Mon Dec 19 06:48:34 2005 on
> zoon.lafn.org
> X-Virus-Status: Clean
> X-UIDL: k/9"!0PO"!L>'!!`)&"!
>
>
>
> SPAM-TRAP,
>
> I can't wait to speak to you about your finances in California. I am
> your personal account manager. I am emailing to let you know that your
> application will be approved, and that you may be eligible for our
> exclusive low rates.
>
> If you would like to apply for these rates, I ask that you fill out
> this short form.
>
> ... "