[Snort-users] How to detect OS with Snort?

Joel Esler jesler at ...1935...
Wed May 16 09:17:05 EDT 2012




On May 8, 2012, at 7:06 PM, Kevin Ross wrote:

> I take it this is due to a policy enforcement in which windows is not allowed? p0f may be a more useful tool to run for this to passively try and fingerprint the OS as it passes. If you are trying to do it via user agent something like this may work:
> 
> alert tcp $HOME_NET any -> any any (msg:"WINDOWS User Agent Detected"; flow:established,to_server; content:"Windows"; nocase; http_header; pcre:"/User\x2DAgent\x3A\x20[^\r\n]*Windows/Hi"; classtype:policy-violation; sid:149881; rev:1;)

User Agents can be spoofed.  Easily.  Trivially.


> 
> I don't think snort is the best for this though. If it is actual attacks you are better off looking at detecting attacks from existing sigs that are out there.
> 
> If you don't mind me asking so we can understand what you are trying to get to: why is it you want to detect Windows machines on your network? If it is enforcement I would look at making the case for other tools such as packetfence http://www.packetfence.org/home.html but I will try and think of something if you let me know what you hope to achieve with this so I understand what you need to look at.

In OpenSource land, p0f is the best tool to go about detecting OSes.

--
Joel Esler
Senior Research Engineer, VRT
OpenSource Community Manager
Sourcefire


> 
> 
> On 8 May 2012 14:26, Borja Luaces <borja.luaces at ...11827...> wrote:
> Good afternoon,
> 
> First of all I have to say that I am new to Snort.
> 
> I am trying to create an alert rule to detect the OS but everytime I try it it seems not to work.
> 
> The rule looks like the following one:
> 
> alert tcp any any -> any any (content:"Windows NT";msg:"Microsoft OS detected";)
> 
> Any help?
> 
> Thanks for your time
> 
> -- 
> Borja Luaces Altares
> Administrador/Analista de Sistemas (MCSE Security,C|EH & CSSA)





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