Get back at CodeRed and Nimbus worms

This tip addresses LaBrea, a GNU Free License utility.

This tip was submitted to the searchSecurity Tip Exchange Contest by user Rick Pierides. Let other users know how useful it is by rating the tip below.

LaBrea is a GNU Free License utility being talked about in the various hacker newsgroups that seems to have some intriguing possibilities for trottling the throats of the scans instituted by the CodeRed and Nimbus variety of worms.

In essence, LaBrea uses the pool of unused IP addresses on your network (those that are not assigned to any physical device) to tie up threads of a CodeRed scan -- sort of a reverse distributed denial-of-service attack with very little of your own bandwidth being used. A scan comes in on your router, the router attempts to find the MAC address for that IP address, to which LaBrea ARPs back a fake MAC address after determining that no real interface has this IP assigned to it. The TCP REQ is ACKd and a minumum Window Size is set and CodeRed (or Nimbus or any plain old scanner) thinks it has a live connection. What it really has is a virtual machine whose only intent is on tying up the thread -- sort of a honeypot for scans (or as the author of this utility puts it, a Tarpit).

Interesting concept. The white paper and the open-source code is available at:

I will be getting my hands dirty looking it over before trying it out with NMAP to see if it can tie up my scanner without eating up bandwidth.

LaBrea TarPit is available at:

This was first published in September 2001

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