[Snort-sigs] netbios rule question

Alex Kirk alex.kirk at ...435...
Wed Dec 1 06:09:09 EST 2004

Given that you're saying these hosts are all internal to your network, 
and that these rules both take the form of:

alert tcp $EXTERNAL_NET any -> $HOME_NET 445

have you checked that your $EXTERNAL_NET and $HOME_NET variables are set 

Alex Kirk
Research Analyst
Sourcefire, Inc.

> Hi All
> I had a question regarding netbios rules. Lately I have been receiving 
> a lot of the alerts as shown below where A.A.A.A and B.B.B.B are all 
> internal hosts to my network. In addition B.B.B.B is the IP address of 
> our domain controller.  Is this merely false positiive or something i 
> should be concerned about. How do I go abt troubleshooting further to 
> see what exactly is happenig. Any help will be appreciated
> Thanks
> Ravi
> [**] [1:2466:4] NETBIOS SMB-DS IPC$ share unicode access [**]
> [Classification: Generic Protocol Command Decode] [Priority: 3]
> 11/30-14:05:00.173386 A.A.A.A:1105 -> B.B.B.B:139
> TCP TTL:128 TOS:0x0 ID:22636 IpLen:20 DgmLen:128 DF
> ***AP*** Seq: 0xD1482D9A  Ack: 0x4A54B89D  Win: 0xFFFF  TcpLen: 20
> [**] [1:2404:5] NETBIOS SMB-DS Session Setup AndX request unicode 
> username overflow attempt [**]
> [Classification: Attempted Administrator Privilege Gain] [Priority: 1]
> 11/30-14:05:00.163386  A.A.A.A:1105 -> B.B.B.B:445
> TCP TTL:128 TOS:0x0 ID:22635 IpLen:20 DgmLen:1440 DF
> ***AP*** Seq: 0xD1482822  Ack: 0x4A54B769  Win: 0xFAB7  TcpLen: 20
> [Xref => 
> http://www.eeye.com/html/research/advisories/ad20040226.html][Xref => 
> http://www.securityfocus.com/bid/9752]
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