Snort mailing list archives
Re: best way to match on CIFS filenames?
From: Todd Wease <twease () sourcefire com>
Date: Fri, 23 May 2008 08:14:14 -0400
You can use the "nocase" option to your content. There is no unicode normalization. You'll have to write a unicode and ascii rule. Something like: alert tcp $EXTERNAL_NET any -> $HOME_NET [445,139] (msg:"SMB unicode rule"; flow:to_server,established; content:"|00|"; depth:1; content:"|FF|SMB"; depth:4; offset:4; content:"f|00|i|00|l|00|e|00|"; nocase; sid:1000001;) alert tcp $EXTERNAL_NET any -> $HOME_NET [445,139] (msg:"SMB ascii rule"; flow:to_server,established; content:"|00|"; depth:1; content:"|FF|SMB"; depth:4; offset:4; content:"file"; nocase; sid:1000002;) You might have to tune these for the different SMB commands a client can use to open/create a file - Open, OpenAndX, NtCreateAndX, etc. Jason Haar wrote:
I'm trying to write a rule to capture uploads of certain filenames via CIFS. However, over the years SMB became CIFS, Unicode was introduced, etc, etc. Which leads to the current mess whereby my "rule" is turning into "rules" as I try to figure out all the combinations. Anyway, I was wondering if there was any built-in 'normalizing' function I could use so that I could look for strings without worrying about their case or unicode status. e.g. a filename of "ntldr.exe" can be "NTLDR.EXE", "Ntldr.exE" as well as "n|00|T|00|l|00|D|00|r|00|.|00|e|00|x|00|e". I am making so many fat-finger mistakes getting that right that I'm hoping the Sourcefire guys have too ;-)
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Current thread:
- best way to match on CIFS filenames? Jason Haar (May 22)
- Re: best way to match on CIFS filenames? Todd Wease (May 23)