Discussion:
[Snort-users] data from multiple sessions in one alert/packet
(too old to reply)
Jon Hart
2006-05-17 21:26:21 UTC
Permalink
Hello

The weird behavior I'm seeing is what appears to be multiple HTT
requests (sometimes the src<->dest is the same, others not) in the sam
alert.

Someone in #snort asked if I was behind a proxy server and, yes, th
bulk of our inbound traffic is handled by Akamai. I can't find an
specific examples, but I swear I saw alerts where some of the traffi
came from Akamai and others did not

Whats is even weirder is, today, I saw and alert that contained portion
of two distinct conversations, but one was headed inbound and the othe
was headed outbound. Aside from the general weirdness of this, I ha
just recently switched my $HOME_NET to 'any'

This is snort 2.4.4, running Red Hat Enterprise Linux ES releas
4 (Nahant Update 1) with kernel 2.6.9-11.ELsmp (not my choice). M
config is more or less stock

var HOME_NET an
var EXTERNAL_NET an
var DNS_SERVERS $HOME_NE
var SMTP_SERVERS $HOME_NE
var HTTP_SERVERS $HOME_NE
var SQL_SERVERS $HOME_NE
var TELNET_SERVERS $HOME_NE
var SNMP_SERVERS $HOME_NE
var HTTP_PORTS 8
var SHELLCODE_PORTS !8
var ORACLE_PORTS 152
var SSH_PORTS 2
var AIM_SERVER
[64.12.24.0/23,64.12.28.0/23,64.12.161.0/24,64.12.163.0/24,64.12.200.0/24,205.188.3.0/24,205.188.5.0/24,205.188.7.0/24,205.188.9.0/24,205.188.153.0/24,205.188.179.0/24,205.188.248.0/24
var RULE_PATH ./rule
config disable_decode_alert
config disable_tcpopt_experimental_alert
preprocessor flow: stats_interval 0 hash
preprocessor frag3_global: max_frags 6553
preprocessor frag3_engine: policy first detect_anomalie
preprocessor stream4: disable_evasion_alert
preprocessor stream4_reassembl
preprocessor http_inspect: global
iis_unicode_map unicode.map 1252
preprocessor http_inspect_server: server default
profile all ports { 80 8080 8180 } oversize_dir_length 500
no_alert
preprocessor rpc_decode: 111 3277
preprocessor b
preprocessor telnet_decod
preprocessor xlink2state: ports { 25 691
output database: log, mysql, user=snort
password=ffffff dbname=snort host=localhost sensor_name=edg

And snort is started as follows

snort -u snort -g snort -i bond0 -c /usr/local/stow/snort/etc/snort.con
-D -ey

(I have a pass rule to filter out a particularly false-positive pron
URL, hence the -o

Any ideas

-jo

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nikns
2006-05-17 21:52:47 UTC
Permalink
I had identical issue. You are probably dropping packets

Short answer is
"There is a config parameter in Stream4 to help address that
On the stream4_reassemble line, add "zero_flushed_packets"
This will cause Stream4 to zero out the memory of th
rebuilt packet before copying in the new data. So, whe
packets are missing from the middle of the rebuilt packet
you'll get 0x00 in those bytes, rather than whatever wa
there from the previous rebuild." <c> Steve

nikn
Post by Jon Hart
Hello
The weird behavior I'm seeing is what appears to be multiple HTT
requests (sometimes the src<->dest is the same, others not) in the sam
alert. =2
Someone in #snort asked if I was behind a proxy server and, yes, th
bulk of our inbound traffic is handled by Akamai. I can't find an
specific examples, but I swear I saw alerts where some of the traffi
came from Akamai and others did not
Whats is even weirder is, today, I saw and alert that contained portion
of two distinct conversations, but one was headed inbound and the othe
was headed outbound. Aside from the general weirdness of this, I ha
just recently switched my $HOME_NET to 'any'
This is snort 2.4.4, running Red Hat Enterprise Linux ES releas
4 (Nahant Update 1) with kernel 2.6.9-11.ELsmp (not my choice). M
config is more or less stock
var HOME_NET an
var EXTERNAL_NET an
var DNS_SERVERS $HOME_NE
var SMTP_SERVERS $HOME_NE
var HTTP_SERVERS $HOME_NE
var SQL_SERVERS $HOME_NE
var TELNET_SERVERS $HOME_NE
var SNMP_SERVERS $HOME_NE
var HTTP_PORTS 8
var SHELLCODE_PORTS !8
var ORACLE_PORTS 152
var SSH_PORTS 2
var AIM_SERVER
[64.12.24.0/23,64.12.28.0/23,64.12.161.0/24,64.12.163.0/24,64.12.200.0/24,
205.188.3.0/24,205.188.5.0/24,205.188.7.0/24,205.188.9.0/24,205.188.153.0/2
4,205.188.179.0/24,205.188.248.0/24
Post by Jon Hart
var RULE_PATH ./rule
config disable_decode_alert
config disable_tcpopt_experimental_alert
preprocessor flow: stats_interval 0 hash
preprocessor frag3_global: max_frags 6553
preprocessor frag3_engine: policy first detect_anomalie
preprocessor stream4: disable_evasion_alert
preprocessor stream4_reassembl
preprocessor http_inspect: global
iis_unicode_map unicode.map 1252=2
preprocessor http_inspect_server: server default
profile all ports { 80 8080 8180 } oversize_dir_length 500
no_alert
preprocessor rpc_decode: 111 3277
preprocessor b
preprocessor telnet_decod
preprocessor xlink2state: ports { 25 691
output database: log, mysql, user=snort
password=ffffff dbname=snort host=localhost sensor_name=edg
And snort is started as follows
snort -u snort -g snort -i bond0 -c /usr/local/stow/snort/etc/snort.con
-D -ey
(I have a pass rule to filter out a particularly false-positive pron
URL, hence the -o
Any ideas
-jo
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ie
Post by Jon Hart
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12164
Post by Jon Hart
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Jon Hart
2006-05-18 16:38:28 UTC
Permalink
Post by nikns
I had identical issue. You are probably dropping packets
I am dropping packets

May 18 09:35:51 xxxxx snort[2252]: Snort received 216724389 packets
May 18 09:35:51 xxxxx snort[2252]: Analyzed: 215806721(99.577%)
May 18 09:35:51 xxxxx snort[2252]: Dropped: 917668(0.423%)
Post by nikns
Short answer is
"There is a config parameter in Stream4 to help address that
On the stream4_reassemble line, add "zero_flushed_packets"
This will cause Stream4 to zero out the memory of th
rebuilt packet before copying in the new data. So, whe
packets are missing from the middle of the rebuilt packet
you'll get 0x00 in those bytes, rather than whatever wa
there from the previous rebuild." <c> Steve
That does work, but now I get 0x00's in the missing portions of th
packet. This is better, though I'd rather not be dropping any packet
at all

Thanks

-jo

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Joel Esler
2006-05-18 18:07:08 UTC
Permalink
Jon

What type of output module are you using

Joe
Post by Jon Hart
Post by nikns
I had identical issue. You are probably dropping packets
I am dropping packets
May 18 09:35:51 xxxxx snort[2252]: Snort received 216724389 packets
May 18 09:35:51 xxxxx snort[2252]: Analyzed: 215806721(99.577%)
May 18 09:35:51 xxxxx snort[2252]: Dropped: 917668(0.423%)
Post by nikns
Short answer is
"There is a config parameter in Stream4 to help address that
On the stream4_reassemble line, add "zero_flushed_packets"
This will cause Stream4 to zero out the memory of th
rebuilt packet before copying in the new data. So, whe
packets are missing from the middle of the rebuilt packet
you'll get 0x00 in those bytes, rather than whatever wa
there from the previous rebuild." <c> Steve
That does work, but now I get 0x00's in the missing portions of th
packet. This is better, though I'd rather not be dropping any packet
at all
Thanks
-jo
------------------------------------------------------
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Joel Esler -- Senior Security Consultant, SFCE - 1-706-627-210
Sourcefire - Security for the /Real/ World -- http://www.sourcefire.co
Snort - Open Source Network IPS/IDS -- http://www.snort.or
GPG Key -- http://demo.sourcefire.com/jesler.pgp.ke
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kritikus Araklidas
2006-05-18 22:07:59 UTC
Permalink
Hi everyone

I have installed the snort 2.4.4 and after some week monitoring my network
i'm still working on threads suppresion, so, some of them work fine but,
some of then doesn't work like the following

GEN:SID 1:1

Message Sorry, no such sid-gen (1:16

I configure on threshold.conf file the supression rule like

suppress gen_id 1, sig_id 16, track by_src, ip X.X.X.0/2

But the suppresion doesn't work, the same thing happend with the GEN:SID
with no information on snort database

Any idea is appreciated

Regards

Chris

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Joel Esler
2006-05-18 22:47:59 UTC
Permalink
-----BEGIN PGP SIGNED MESSAGE----
Hash: SHA

There is no sid of 16. What alert are you trying to suppress? Are =2
you trying to suppress "http_inspect: OVERSIZE CHUNK ENCODING"

That would be gen_id 119, sig_id 16

Check out your gen-msg.map and sid-msg.map in your etc/ directory in =2
Snort

Joe
Post by kritikus Araklidas
Hi everyone
I have installed the snort 2.4.4 and after some week monitoring my =2
network i'm still working on threads suppresion, so, some of them =2
work fine but, some of then doesn't work like the following
GEN:SID 1:1
Message Sorry, no such sid-gen (1:16
I configure on threshold.conf file the supression rule like
suppress gen_id 1, sig_id 16, track by_src, ip X.X.X.0/2
But the suppresion doesn't work, the same thing happend with the =2
GEN:SID with no information on snort database
Any idea is appreciated
Regards
Chris
________________________________________________________________
Is your PC infected? Get a FREE online computer virus scan from =2
McAfee® Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?
cid=396
------------------------------------------------------
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security
Get stuff done quickly with pre-integrated technology to make your =2
job easie
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Geronim
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cmd=lnk&kid=120709&bid=263057&dat=12164
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bNoOGfRO7UKz4EfNIyqRlUI=3
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kritikus Araklidas
2006-05-22 20:04:11 UTC
Permalink
Hi everyone

I have installed the snort 2.4.4 and after some week monitoring m
network i'm try to select some alarms and send the resume via email but it's
fail, any idea, i have configure my sendmail for send any email to our
corporate email server configuring the DS parameter. In the base page looks
the email was sucesfully sended but the email never arrives to the email
server

Any idea is apreciated

Regards

Cris

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Jon Hart
2006-05-18 22:11:36 UTC
Permalink
Post by Joel Esler
Jon
What type of output module are you using
Joe
I'm using the database output plugin. I know that can be a proble
under high load, right? Is that high alert load or just high pps loa
in general? My signatures are fairly tight so we get maybe 10-2
hits/hour, though occassionally we'll get a peak when someone scans u
for something

I had been using barnyard, but dumped it while attempting to debu
another problem. If barnyard will help here, I'll do that again

-jo

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Joel Esler
2006-05-18 22:50:04 UTC
Permalink
-----BEGIN PGP SIGNED MESSAGE----
Hash: SHA

Snort has to eat alot of cycles to input stuff into the DB, while it
is doing that, it's not sniffing as efficiently as it should

Snort should output to either one of two things A) pcap binary, or B)
Unified binary. Preferred method recommended from me is always going
to be Unified, have barnyard read that unified file and input stuff
into the db

A.k.a. Don't have your IDS inserting into a DB, let your IDS be an
IDS, let barnyard insert into DB

Joe
Post by Jon Hart
Post by Joel Esler
Jon
What type of output module are you using
Joe
I'm using the database output plugin. I know that can be a proble
under high load, right? Is that high alert load or just high pps loa
in general? My signatures are fairly tight so we get maybe 10-2
hits/hour, though occassionally we'll get a peak when someone scans u
for something
I had been using barnyard, but dumped it while attempting to debu
another problem. If barnyard will help here, I'll do that again
-jo
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Michael Scheidell
2006-05-22 22:01:43 UTC
Permalink
Neither snort nor base automatically sends emails
-----Original Message----
kritikus Araklida
Sent: Monday, May 22, 2006 4:04 P
Subject: [Snort-users] Mail Notification Fai
=2
=2
Hi everyone
=2
I have installed the snort 2.4.4 and after some week=2
monitoring my network i'm try to select some alarms and send=2
the resume via email but it's=2
fail, any idea, i have configure my sendmail for send any=2
email to our=2
Snort does not send email
corporate email server configuring the DS parameter. In the=2
base page looks=2
the email was sucesfully sended but the email never arrives=2
to the email=2
server
Are you talking about the package 'BASE'? It doesn't automatically sen
emails either

If a different package, you need to talk to the support people of tha
package

If a sendmail problem, look at your mail logs

------------------------------------------------------
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