[Snort-users] Garbage in snort logs

russell R.FULTON at ...3809...
Sun Jan 6 20:28:03 EST 2002


Greetings All,
	     A while back I reported that I was getting 'garbage' appended to
the packets logged by snort and that these packets also had 0 for the
MAC address.

Since my initial report I have installed a new instance of snort (1.8.3)
on a different system and verified that the problem still exists.  I
also reinstalled libpcap using the latest from www.tcpdump.org.

Both systems I tested this on were running Debian linux:
Linux debian 2.4.12-itss1 #1 Mon Oct 15 06:55:58 NZDT 2001 i686 unknown

Appended is an example of an offending log record.  I believe that the
real record terminates after "Connection close" and that the rest of the
'packet' is just stuff that was in the buffer from some other packet.

I suspect that the packet length is getting corrupted somewhere along
the line...  Hmmm I just noticed that the IP Type is also 0x0 for these
packets.  So it looks like something is overwriting the ethernet headers
and the first part of the IP header including the length.

I originally had a problem with an older version of snort (1.8.0 ?)
where I would get the alerts (with 0 MAC addresses) but no packets
logged.  Marty advised me to upgrade to 1.8.2 as there had been a bug in
the packet logging code. When I did so I got the current behaviour. I
suspect that this fix was incomplete in some way and something in my
setup tickles this bug.

What I find totally baffling is why this should just affect *me*!

Cheers, Russell.

[**] WEB-IIS .... access [**]
01/07-15:28:20.028524 0:0:0:0:0:0 -> 0:0:0:0:0:0 type:0x0 len:0x25A
130.123.128.24:3024 -> 130.216.191.67:80 TCP TTL:240 TOS:0x10 ID:0
IpLen:20 DgmLen:588
***AP*** Seq: 0x215073A1  Ack: 0x74F26D2D  Win: 0x40E8  TcpLen: 20
47 45 54 20 2F 73 63 72 69 70 74 73 2F 2E 2E 5C  GET /scripts/..\
2E 2E 2F 77 69 6E 6E 74 2F 73 79 73 74 65 6D 33  ../winnt/system3
32 2F 63 6D 64 2E 65 78 65 3F 2F 63 2B 64 69 72  2/cmd.exe?/c+dir
20 72 20 64 69 72 20 48 54 54 50 2F 31 2E 30 0D   r dir HTTP/1.0.
0A 48 6F 73 74 3A 20 77 77 77 0D 0A 43 6F 6E 6E  .Host: www..Conn
6E 65 63 74 69 6F 6E 3A 20 63 6C 6F 73 65 0D 0A  nection: close..
0D 0A 69 74 74 6C 65 20 68 6F 74 21 26 6E 62 73  ..ittle hot!&nbs
70 3B 20 57 65 20 77 65 6E 74 20 74 6F 20 74 68  p; We went to th
65 20 53 68 72 75 62 62 65 72 79 20 66 6F 72 20  e Shrubbery for
61 20 64 72 69 6E 6B 20 61 6E 64 20 77 61 74 63  a drink and watc
68 65 64 20 74 68 65 20 6F 6E 65 20 61 6E 64 20  hed the one and
6F 6E 6C 79 20 53 61 6D 6F 61 6E 20 42 6F 62 20  only Samoan Bob
4D 61 72 6C 65 79 20 6A 61 6D 20 77 69 74 68 20  Marley jam with
68 69 73 20 6D 61 74 65 20 2D 20 79 6F 75 20 6D  his mate - you m
75 73 74 20 74 65 6C 6C 20 45 73 74 68 65 72 21  ust tell Esther!
26 6E 62 73 70 3B 20 41 6C 73 6F 20 63 6F 75 6C    Also coul
64 20 79 6F 75 20 73 61 79 20 74 68 61 6E 6B 73  d you say thanks
20 74 6F 20 59 76 6F 6E 6E 65 20 66 6F 72 20 74   to Yvonne for t
68 65 20 6C 65 61 76 69 6E 67 20 6D 65 61 6C 20  he leaving meal
70 61 72 74 69 63 75 6C 61 72 6C 79 20 74 68 65  particularly the
20 63 68 61 6D 70 65 72 73 20 2D 20 61 6E 64 26   champers - and&
6E 62 73 70 3B 68 65 72 65 27 73 20 6D 79 20 55  nbsp;here's my U
4B 20 61 64 64 72 65 73 73 20 28 74 68 6F 75 67  K address (thoug
68 74 20 4D 61 72 79 20 64 6F 65 73 20 68 61 76  ht Mary does hav
65 20 69 74 20 75 70 73 74 61 69 72 73 21 29 3C  e it upstairs!)<
2F 50 3E 0D 0A 3C 50 3E 34 35 20 41 6C 62 65 72  /P>..<P>45 Alber
74 20 52 6F 61 64 2C 20 57 61 6C 74 68 61 6D 73  t Road, Walthams
74 6F 77 2C 20 4C 6F 6E 64 6F 6E 2C 20 45 31 37  tow, London, E17
20 37 50 52 2E 3C 2F 50 3E 0D 0A 3C 50 3E 54 68   7PR.</P>..<P>Th
61 6E 6B 73 20 6D 79 20 64 65 61 72 2E 3C 2F 50  anks my dear.</P
3E 0D 0A 3C 50 3E 41 6E 64 20 68 65 6C 6C 6F 20  >..<P>And hello
74 6F 20 74 68 65 20 44 6D 20 74 65 61 6D 3C 2F  to the Dm team</
50 3E 0D 0A 3C 50 3E 57 69 6C 6C 20 77 72 69 74  P>..<P>Will writ
65 20 73 6F 6F 6E 20 28 65 70 2D 61 6C 69 76 65  e soon (ep-alive
0D 0A                                            ..

=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+


I am installing from the tarball so I can add some diagnostics if anyone
has suggestions.

-- 
Russell Fulton, Computer and Network Security Officer
The University of Auckland,  New Zealand







More information about the Snort-users mailing list