[Snort-users] Understanding the alert file

Gabriel Corre gabriel.corre at ...17281...
Thu Aug 13 03:36:55 EDT 2015


Hi,

If you’re still looking for a way of doing this : « It would be nice to only have one alert sent per minute but I'm getting many from the same cron job for that minute “
You should use try something like this : alert tcp any any -> any 80 (msg:”Heartbeat”; content:”/testheartbeat123”; http_uri; threshold:type limit, track by_src, count 1, seconds 60; classtype:not-suspicious; sid:1;)

It should log just 1 alert per minute.

You can have a look at the Snort Manual p.233 for more details and examples ;)

Cheers!
--

Gabriel Corré
Élève Ingénieur Réseaux, Ops - Core Infrastructure

De : Joel Esler (jesler) [mailto:jesler at ...589...]
Envoyé : mercredi 12 août 2015 16:51
À : usa ims <usaims at ...131...>
Cc : snort-users at lists.sourceforge.net
Objet : Re: [Snort-users] Understanding the alert file

Awesome.  Sounds good.

On Aug 12, 2015, at 10:38 AM, usa ims <usaims at ...131...<mailto:usaims at ...131...>> wrote:

My issue is resolved by correcting the rule that was suggested by Joel. Thank you from South Florida. Additionally, the link provided by James were very useful.


On Tuesday, August 11, 2015 6:37 PM, Joel Esler (jesler) <jesler at ...589...<mailto:jesler at ...589...>> wrote:

I think what you mean to have is:

alert tcp any any -> any 80 (msg:”Heartbeat”; content:”/testheartbeat123”; http_uri; classtype:not-suspicious; sid:1;)


On Aug 11, 2015, at 5:43 PM, usa ims <usaims at ...131...<mailto:usaims at ...131...>> wrote:



Snort 2.9.2.2 on RaspberryPi
I am trying to understand the 'alert' file.

I am implementing a hearbeat rule so that I can check for lost packets while the system is being slammed. Here is the rule:

alert tcp any any -> any 80 (msg:" Heartbeat" content:/testheartbeat123"; classtype:not-suspicious;sid:1;)

I have a cron job being fired off every minute from a host on the EXTERNAL_NET:
* * * * * perl -MLWP::UserAgent -e 'LWP::UserAgent->new()->get("http://example.com/testheartbeat123");'
> /dev/null 2>&1

In the alert file, it contains:

[**] [1:1:0]  Heartbeat" content:/testheartbeat123 [**]
[Classification: Not Suspicious Traffic] [Priority: 3]
08/11-15:45:09.182768 192.168.0.99:36310 -> 192.168.24.24:80
TCP TTL:64 TOS:0x0 ID:56030 IpLen:20 DgmLen:60 DF
******S* Seq: 0xAFDDBF49  Ack: 0x0  Win: 0x7210  TcpLen: 40
TCP Options (5) => MSS: 1460 SackOK TS: 8611223 0 NOP WS: 6

[**] [1:1:0]  Heartbeat" content:/testheartbeat123 [**]
[Classification: Not Suspicious Traffic] [Priority: 3]
08/11-15:45:09.184943 192.168.0.99:36310 -> 192.168.24.24:80
TCP TTL:64 TOS:0x0 ID:56031 IpLen:20 DgmLen:52 DF
***A**** Seq: 0xAFDDBF4A  Ack: 0x4AD89C91  Win: 0x1C9  TcpLen: 32
TCP Options (3) => NOP NOP TS: 8611223 8328656

[**] [1:1:0]  Heartbeat" content:/testheartbeat123 [**]
[Classification: Not Suspicious Traffic] [Priority: 3]
08/11-15:45:09.975764 192.168.0.99:36310 -> 192.168.24.24:80
TCP TTL:64 TOS:0x0 ID:56032 IpLen:20 DgmLen:180 DF
***AP*** Seq: 0xAFDDBF4A  Ack: 0x4AD89C91  Win: 0x1C9  TcpLen: 32
TCP Options (3) => NOP NOP TS: 8611302 8328656

[**] [1:1:0]  Heartbeat" content:/testheartbeat123 [**]
[Classification: Not Suspicious Traffic] [Priority: 3]
08/11-15:45:09.981515 192.168.0.99:36310 -> 192.168.24.24:80
TCP TTL:64 TOS:0x0 ID:56033 IpLen:20 DgmLen:52 DF
***A**** Seq: 0xAFDDBFCA  Ack: 0x4AD89E7D  Win: 0x1D9  TcpLen: 32
TCP Options (3) => NOP NOP TS: 8611303 8328736

[**] [1:1:0]  Heartbeat" content:/testheartbeat123 [**]
[Classification: Not Suspicious Traffic] [Priority: 3]
08/11-15:45:10.019413 192.168.0.99:36310 -> 192.168.24.24:80
TCP TTL:64 TOS:0x0 ID:56034 IpLen:20 DgmLen:52 DF
***A**** Seq: 0xAFDDBFCA  Ack: 0x4AD89E7E  Win: 0x1D9  TcpLen: 32
TCP Options (3) => NOP NOP TS: 8611307 8328736

[**] [1:1:0]  Heartbeat" content:/testheartbeat123 [**]
[Classification: Not Suspicious Traffic] [Priority: 3]
08/11-15:45:10.116771 192.168.0.99:36310 -> 192.168.24.24:80
TCP TTL:64 TOS:0x0 ID:56035 IpLen:20 DgmLen:52 DF
***A***F Seq: 0xAFDDBFCA  Ack: 0x4AD89E7E  Win: 0x1D9  TcpLen: 32
TCP Options (3) => NOP NOP TS: 8611316 8328736

[**] [1:1:0]  Heartbeat" content:/testheartbeat123 [**]
[Classification: Not Suspicious Traffic] [Priority: 3]
08/11-15:45:10.116771 192.168.0.99:36310 -> 192.168.24.24:80
TCP TTL:64 TOS:0x0 ID:56035 IpLen:20 DgmLen:52 DF
***A***F Seq: 0xAFDDBFCA  Ack: 0x4AD89E7E  Win: 0x1D9  TcpLen: 32
TCP Options (3) => NOP NOP TS: 8611316 8328736

I need help understanding the '***????***'.

It would be nice to only have one alert sent per minute but I'm getting many from the same cron job for that minute. It's going to be cumbersome looking through the alert logs looking for lost alerts to see if any packets were lost. This rule was taken from Martin's blog. Any suggestions, comments, etc.


usaims
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