[Snort-users] UPDATE: flexresp2 (new and improved active response for Snort)

Jeff Nathan jeff at ...950...
Thu Sep 4 03:00:12 EDT 2003

Hash: SHA1

NOTE: This is an update to the release of sp_respond2 yesterday based  
upon feedback from Chris Green.  It contains 2 minor bugfixes, allows  
for running Snort as a non-root user with active response and re-adds  
the ability to send TCP resets to the client (ONLY to be used for  
attack-response rules).

At long last I am proud to release flexresp2, the improved version of  
active response for Snort.

 From the readme file:
To compensate for the fact that Snort cannot possibly send a TCP reset  
to the server (receiving host) or client (sending host) before the  
offending packet reaches the destination, Snort will transmit a minimum  
of 3 TCP reset packets with shifting TCP ack numbers in an attempt to  
brute-force the connection into an unusable state.

Flexresp2 will automatically calculate the original TTL when sending a  
response packet.

Flexresp2 will not respond to TCP packets with the SYN, FIN or RST flag  

Link-layer active response (crafting complete Ethernet frames) can be  
used to completely bypass the routing table and force response packets  
to be sent out a specified interface.

Snort running on Unix-like systems no longer requires root privileges  
when active response (flexresp2) is used.  Instead the -u and -g  
command line options can be used.

All the files comprising flexresp2 (sp_respond2) are available here:

A readme is available here:

Please read this readme document carefully.  It has been written to  
help anyone interested in using flexresp2 and details the new features  
available in this release.

All the files have been MD5 checksummed, a checksum file is available  

A detached PGP signature has been created for all the files.  To verify  
the signatures using GPG, import my public key from the MIT keyserver  
using the command:

gpg --keyserver pgp.mit.edu --recv-key 6923D3FD

Once you have obtained my PGP public key, you can verify the integrity  
of the flexresp2 files using commands resembling the following:

gpg --verify sp_respond2.diff.gz.asc sp_respond2.diff.gz

Please reference the BUGS file contained with the Snort distribution  
before reporting any bugs in this software.

Special thanks to Dragos Ruiu, Jed Haile, Jose Nazario, Mike Davis,  
Chris Reid and Chris Green for all their suggestions and review.



- --
http://cerberus.sourcefire.com/~jeff       (gpg key available)
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