[Snort-users] Homenet Question

Gibson, Samuel gibsons at ...15616...
Fri May 4 13:15:46 EDT 2012


I forgot to mention the Sensitive_data threshold exceeded alert (GID: 139 Sig: 1) that I assume gets triggered due to the amount of sensitive_data email alerts.  Sorry if I should have made this another thread.

________________________________________
From: Gibson, Samuel [gibsons at ...15616...]
Sent: Friday, May 04, 2012 12:08 PM
To: snort-users at lists.sourceforge.net
Subject: Re: [Snort-users] Homenet Question

Thanks for your help.  This is sort of a follow-on question.

I have updated EXTERNAL_NET to !$HOME_NET and that seems to have helped with some of the rules but, am I correct in thinking it should stop the sensitive_data email alerts between internal resources and VPN clients?

# alert tcp $HOME_NET any -> $EXTERNAL_NET [80,20,25,143,110] (msg:"SENSITIVE-DATA Email Addresses"; metadata:service http, service smtp, service ftp-data, service imap, service pop3; sd_pattern:20,email; classtype:sdf; sid:5; gid:138; rev:1;)

I get loads of these due to a large volume of emails to VPN clients.
________________________________________
From: Gibson, Samuel [gibsons at ...15616...]
Sent: Wednesday, May 02, 2012 4:40 PM
To: snort-users at lists.sourceforge.net
Subject: Re: [Snort-users] Homenet Question

Thanks guys.  I will try setting EXTERNAL_NET to !$HOME_NET.


________________________________________
From: Ian Bowers [iggdawg at ...11827...]
Sent: Wednesday, May 02, 2012 12:11 PM
To: Adam Gardner
Cc: Gibson, Samuel; snort-users at lists.sourceforge.net
Subject: Re: [Snort-users] Homenet Question

Alternately, if you have some reason for using "any" as EXTERNAL_NET, you can change the variable in the rule from EXTERNAL_NET to !$HOME_NET.  If you use PulledPork, place this in modifysid.conf :

2009702 "$EXTERNAL_NET" "!$HOME_NET"

However I imagine similar issue will come up in other rules.  Adam's solution is probably the best way to go.

-Ian

On Wed, May 2, 2012 at 10:13 AM, Adam Gardner <adamgardner502 at ...11827...<mailto:adamgardner502 at ...11827...>> wrote:
Since your $EXTERNAL_NET is set to "any" 10.0.0.0/8<http://10.0.0.0/8> is included in that.  You'll probably want to set $EXTERNAL_NET to !$HOME_NET.


On Wed, May 2, 2012 at 9:46 AM, Gibson, Samuel <gibsons at ...15616...<mailto:gibsons at ...15616...>> wrote:
Hello,

I am having an interesting issue with the homenet.  I have it setup in snort.conf as follows:

ipvar HOME_NET [10.0.0.0/8<http://10.0.0.0/8>]

ipvar EXTERNAL_NET any

ipvar DNS_Servers [10.1.2.3,10.1.2.4]

Which we have subnetted into internal networks similar to 10.1.2.x, 10.2.3.x and so on.  However our VPN clients use 10.1.20.x/24.

Whenever a VPN Client registers itself in DNS after connecting, I get an ET POLICY DNS Update From External net  (Gen 1 Sig 2009702)

The rule triggers, for example, with a source of 10.10.20.10 and a destination of 10.1.2.3

I can suppress this, but am mostly wondering if anyone has any insight into why the VPN is not being considered part of HOMENET.

Thanks,
Sam



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