Date: Tue, 12 Feb 2008 08:22:34 -0500
From: Keith Kilroy <keith@...uritynow.us>
To: keith@...uritynow.us
Cc: full-disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Re: Brute force attack - need your advice

Oh yeah be sure not to use html formatted emails to post... Like I  
accidently just did had wrong damn client up. That happens with not  
enough sleep or coffee :(

link within has now been disabled


On Feb 12, 2008, at 8:17 AM, keith@...uritynow.us wrote:

> Hello Tonnerre,
>
> "I personally think that Snort is snake oil."
> It can be a pain to get setup and to actually reduce false  
> positives, been using since begining of project, but requires a lot  
> of learning to setup properly" and as I stated nothing is foolproof  
> or totally secure. Other measures need deployed as well such as an  
> application level firewall. I disagree with the snake oil statement  
> (we'll agree to disagree here) but do agree someone that does not  
> use it on a daily basis it is very hard to work through at first.
>
> "Apart from the fact that you cannot destroy a hard disk in a way that
> makes it unrecoverable (with expensive equipment and time), this is
> pure populism."
>
> It takes quite a bit of heat and even then some data can be  
> recovered, from magnetic residue, in labs. Usually cost prohibitive  
> unless someone really wants your data bad and has a big budget.
>
> But please state a config that someone with experience can not get  
> into, is more of a point that security is ever evolving.
>
> "This is security by obscurity. If you just fiddle with the ports  
> which
> were open for a second, it is pretty easy to determine which service  
> is
> running on it. I see no point at all in all of this port changing."
>
> Yup it is security by obscurity and it will help against a script  
> kiddie that won't take the time to scan all ports, thats why I  
> suggested move to a high non-standard port.
>
> "But I don't agree to ...
>
>> write. Heck you can even google and download some to get you started.
>
> ...using any script Google finds, some have nasty bugs and blacklist
> the wrong hosts (e.g. if you set an user name with spaces). You  
> clearly
> don't want your DNS server blacklisted, for example."
>
> I'm not talking about downloading blacklists but dynamic firewall  
> rules and scripting to achieve a dynamic list based on ranking of  
> attacks against the box. Google does have a few references and  
> examples that can be modified if necessary. I'm going under the  
> assumption that scripting is not second nature to the tech setting up.
>
> Blacklists downloaded, for lack of a better term suck.
>
> Tonnerre I appreciate your comments too, debating is a good thing on  
> things like this.
>
> Keith
>
> <a href="http://www.linkedin.com/in/keithkilroy" ><img src="http://www.linkedin.com/img/webpromo/btn_viewmy_160x25.gif 
> " width="160" height="25" border="0" alt="View Keith Kilroy's  
> profile on LinkedIn"></a>
>
> -----Original Message-----
> From: Tonnerre Lombard <tonnerre.lombard@...roup.ch>
> Sent: Tuesday, February 12, 2008 7:20am
> To: Keith Kilroy <keith@...uritynow.us>
> Cc: Abilash Praveen <contactme@...lashpraveen.com>, full-disclosure <full-disclosure@...ts.grok.org.uk 
> >
> Subject: Re: [Full-disclosure] Brute force attack - need your advice
>
> Salut, Keith,
>
> On Tue, 12 Feb 2008 03:21:20 -0500, Keith Kilroy wrote:
>> Lock down your server so only needed ports are open, move ssh above
>> the norm scan range, setup SNORT and learn how to use it, harden and
>> update all progz. Check for web app holes.....buffer overflows etc.
>
> While I agree with locking down and checking for vulnerabilities, I
> personally think that Snort is snake oil. It hardly ever detected
> attacks for me which could have harmed my systems. (There were quite a
> bunch of them, but they went mostly unnoticed.)
>
> There are behavior based, autolearning IDS modes, but I've had my
> experiences with jumping in public parking lots (which caused terror
> alert because the IDS wasn't used to people jumping), so I am quite
> sceptic of that as well.
>
>> The only box that is safe is the one unplugged hdd removed and
>> destroyed and rest of system locked in a closet.
>
> Apart from the fact that you cannot destroy a hard disk in a way that
> makes it unrecoverable (with expensive equipment and time), this is
> pure populism.
>
>> Just perform your due diligence and watch and archive your logs.
>
> I agree here; and don't log to syslog on localhost, have a separate
> logging host like syslog is intended to be used...
>
>> are targeted at those guys), ever heard of DDOS and botnets. move all
>> default ports you can and have their services report different than
>> what is really there.
>
> This is security by obscurity. If you just fiddle with the ports which
> were open for a second, it is pretty easy to determine which service  
> is
> running on it. I see no point at all in all of this port changing.
>
>> If you are detecting the brute force attacks then you can stop them.
>
> Apart from the bandwidth induced, bruteforce attacks are pretty  
> useless
> if you have sanely chosen passwords. And in the age of Tengig  
> networks,
> the bandwidth penalty is minimal.
>
>> anyway. Just try to stay ahead of the curve. Harden, log, respond. Oh
>> yeah be sure to perform your backups, if someone besides a Script
>
> I totally agree to backups though, for various reasons[1]. ;-)
>
>> [Lines of acute paranoia scrapped]
>> securing your stuff and monitoring with dynamic blocking that times
>> out after a period of time. Rank the attacker when it hits a 5
>> blockem for 30 min then if it reoccurs and they achieve a high score
>
> This is pretty useful for various purposes, also for saving bandwidth
> used by brute force attackers. But I don't agree to ...
>
>> write. Heck you can even google and download some to get you started.
>
> ...using any script Google finds, some have nasty bugs and blacklist
> the wrong hosts (e.g. if you set an user name with spaces). You  
> clearly
> don't want your DNS server blacklisted, for example.
>
> 				Tonnerre
>
> [1]: No, a RAID1 is not a backup.
> -- 
> SyGroup GmbH
> Tonnerre Lombard
>
> Solutions Systematiques
> Tel:+41 61 333 80 33		Güterstrasse 86
> Fax:+41 61 383 14 67		4053 Basel
> Web:www.sygroup.ch		tonnerre.lombard@...roup.ch
>
>
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