[Snort-users] Snort logs web browsing

Matt W. kmx at ...1644...
Mon Apr 16 01:59:30 EDT 2001


You can also get the newest snort and use http_decode_ignore and specify
IP's/ranges just like the port scan ignore preprocessor.

-matt

"shawn . moyer" wrote:

> Basically the http decode preprocessor is catching unicode characters
> and alerting you to this traffic. For the most part, if it's outbound,
> verify that it's valid traffic and you can safely ignore. I've always
> thought that this text should be rewritten as something like "Unicode
> traffic detected", since it's more often than not a false positive.
>
> The reason you get it even with HOME_NET defined is that the http decode
> preprocessor is called before the actual ruleset, so none of the
> variables you set really apply.
>
> In short, investigate, verify, and treat it as informational most of the
> time. If you don't have any webservers on your net that are vulnerable
> to unicode stuff you can probably safely prioritize this one pretty low.
>
> --shawn
>
> Phil wrote:
> >
> > I've got snort working (apparently you need to have -i
> > elxl0 on the command line in order for $elxl0_ADDRESS
> > to work in the config file).
> >
> > So anyway, it's running now, but it seems to be
> > logging ONE outbound web traffic (where X.X.X.X is my
> > external IP):
> >
> > [**] spp_http_decode: IIS Unicode attack detected [**]
> > 04/15-18:08:02.069333 X.X.X.X:1532 ->
> > 207.200.81.187:80
> > TCP TTL:127 TOS:0x0 ID:50983 IpLen:20 DgmLen:1024 DF
> > ***AP*** Seq: 0x8E5AC4  Ack: 0x8EC2A0F0  Win: 0x2238
> > TcpLen: 20
> >
> > And that IP's nslookup:
> > Name:    vwww-rl.netscape.com
> > Address:  207.200.81.187
> >
> > Shows netscape.com which I didn't visit today.
> > Regardless, it's an outgoing connection and I don't
> > quite get it. Here's more relevant info:
> >
> > Solaris 2.6 x86
> > Snort 1.7
> > Updated ruleset today
> > var HOME_NET $elxl0_ADDRESS
> > var EXTERNAL_NET !$HOME_NET
> > command used to start snort:
> > /usr/local/bin/snort -A fast -s -i elxl0 -l
> > /var/log/snortlogs -c /etc/snort/snort.conf -D
> >
> > Any help would be much appreciated.
> >
> > Phil
> >
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> --
>
> s h a w n   m o y e r
> shawn at ...1184...
>
> "Nuclear war would really set back cable."
>                              -- Ted Turner
>
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