[Oisf-devel] FP on complex netbios sig

[Peter Manev]

sorry,
I meant
content:"|00 5C 00 77 00 69 00 .......|" so o

On Tue, Aug 21, 2012 at 11:18 PM, Peter Manev <petermanev at gmail.com> wrote:

> Hi,
>
> What happens if you change all the contents ...
>
> content:"|00 5C 00|w|00|i|00|n|00|r|00|e|00|g|
> 00 00 00|"
> change to content:"5C 00 77 00 69 00 ......." so on ?
>
>
> Thanks
>
> On Wed, Aug 22, 2012 at 1:08 AM, rmkml <rmkml at yahoo.fr> wrote:
>
>> Hi,
>>
>> First, Congratulations for a new Suricata v1.3.1 !
>>
>> ok Im test this new version, and I have a complex netbios FP, based on
>> this old netbios sig:
>>  alert tcp $EXTERNAL_NET any -> $HOME_NET 445 (msg:"NETBIOS SMB-DS winreg
>> unicode create tree attempt"; flow:established,to_server;
>> flowbits:isset,smb.tree.**connect.ipc; content:"|00|"; depth:1;
>> content:"|FF|SMB|A2|"; within:5; distance:3; byte_test:1,&,128,6,relative;
>> pcre:"/^.{27}/R"; content:"|5C 00|w|00|i|00|n|00|r|00|e|00|g|**00 00
>> 00|"; within:16; distance:51; nocase; flowbits:set,smb.tree.create.**winreg;
>> classtype:protocol-command-**decode; sid:2477; rev:6;)
>>
>>
>> ok I small change on this for reply FP with my joigned pcap file:
>> (removed established and two flowbits)
>>  alert tcp $EXTERNAL_NET any -> $HOME_NET 445 (msg:"NETBIOS SMB-DS winreg
>> unicode create tree attempt"; flow:to_server; content:"|00|"; depth:1;
>> content:"|FF|SMB|A2|"; within:5; distance:3; byte_test:1,&,128,6,relative;
>> pcre:"/^.{27}/R"; content:"|5C 00|w|00|i|00|n|00|r|00|e|00|g|**00 00
>> 00|"; within:16; distance:51; nocase; classtype:protocol-command-**decode;
>> sid:2477; rev:66;)
>>
>> ok when I start v1.3.1, suricata fire:
>>  06/11/2012-11:51:51.690598  [**] [1:2477:66] NETBIOS SMB-DS winreg
>> unicode create tree attempt [**] [Classification: Generic Protocol Command
>> Decode] [Priority: 3] {TCP} 172.21.35.149:4345 -> 172.16.142.24:445
>> Of course, snort not fire.
>>
>> ok hexa dump my pcap file:
>> #000000C8 13 38 01 0A 96 A7 00 00 00 64 FF 53 4D 42 A2 00 00 00 00 18
>> .8.......d.SMB......
>> #                            +          ++++ ++++++++   1  2  3  4  5
>> #000000DC 07 C8 00 00 67 E1 67 45 78 C7 9C F1 00 00 06 10 B4 16 02 20
>> ....g.gEx..........
>> #           &128
>> #          6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
>> #000000F0 80 02 18 FF 00 DE DE 00 0E 00 16 00 00 00 00 00 00 00 9F 01
>> ....................
>> #         26 27  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17
>> #00000104 02 00 00 00 00 00 00 00 00 00 00 00 00 00 03 00 00 00 01 00
>> ....................
>> #         18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
>> #00000118 00 00 40 00 00 00 02 00 00 00 03 11 00 00 5C 00 77 00 69 00
>> .. at ...........\.w.i.
>> #                                                    ^
>> #         38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
>> #0000012C 6E 00 72 00 65 00 67 00 00 00 00 00 CC 00 00 00
>> n.r.e.g.........
>>
>>
>> Why Suricata fire?
>>
>> ok modified sig for firing snort with my pcap: (added 0x00 and changed 16
>> -> 17)
>>  alert tcp $EXTERNAL_NET any -> $HOME_NET 445 (msg:"NETBIOS SMB-DS winreg
>> unicode create tree attempt"; flow:to_server; content:"|00|"; depth:1;
>> content:"|FF|SMB|A2|"; within:5; distance:3;
>> byte_test:1,&,128,6,relative; pcre:"/^.{27}/R"; content:"|00 5C
>> 00|w|00|i|00|n|00|r|00|e|00|g|**00 00 00|";
>> within:17; distance:51; nocase; classtype:protocol-command-**decode;
>> sid:2477; rev:67;)
>> and Suricata fire again.
>>
>> If anyone confirm, Im open a new redmine ticket...
>>
>> Regards
>> Rmkml
>>
>> http://twitter.com/rmkml
>> _______________________________________________
>> Oisf-devel mailing list
>> Oisf-devel at openinfosecfoundation.org
>> https://lists.openinfosecfoundation.org/mailman/listinfo/oisf-devel
>>
>
>
>
> --
> Regards,
> Peter Manev
>
>


-- 
Regards,
Peter Manev
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