The Naptha vulnerabilities are a type of denial-of-service vulnerabilities researched and documented by Bob Keyes of BindView’s RAZOR Security Team in 2000. The vulnerabilities exist in some implementations of the TCP protocol, specifically in the way some TCP implementations keep track of the state of TCP connections, and allow an attacker to exhaust the resources of a system under attack without utilizing much resources on the system used to launch the attack.

The following links provide more information about the Naptha denial-of-service vulnerabilities:

• The original BindView advisory is archived here.
• The advisory that CERT/CC published for the Naptha vulnerabilities is here.

The Tool

To study and show the Naptha vulnerabilities, Bob Keyes wrote the Naptha tool. The tool was written in C and used libpcap to read packets from the network and libdnet to craft packets.

The Naptha tool actually consists of two programs: a program called synsend whose only function is to send TCP SYN packets to the target system, and a program called srvr whose function is to respond to specific traffic received from the target system with TCP packets with specific TCP flags set. Both what traffic to respond to and how to respond to it are specified by the user via command-line arguments.

You can download Naptha here:

naptha-1.1.tgz

Or read more here.

A fairly serious flaw that was announced in October 2008 by Outpost24 (and apparently discovered way back in 2005), has finally been patched by the major players Cisco and Microsoft.

So far Redhat has offered a workaround for the flaw and Juniper has responded that their equipment is not vulnerable.

It could be that Juniper doesn’t really understand the attack yet, if so that’s bad news as most of the Internet backbone (ISP Level) runs on Juniper equipment.

Microsoft and Cisco have issued updates that protect against a new class of attack that requires very little bandwidth and can leave servers and routers paralyzed even after a flood of malicious data has stopped.

The bug in the TCP, or transmission control protocol, was disclosed in October by security researchers Jack Louis and Robert E. Lee of Sweden-based Outpost24. It gave many security watchers pause because it provided attackers with a new way to launch potentially crippling attacks on a wide array of equipment used to route traffic over the internet.

“This is definitely momentum and other vendors, once they fully understand what has been talked about here, will come up with mitigation strategies of their own,” Lee told The Register. “This really is good progress from both Microsoft and Cisco.”

Microsoft rolled it out in their normal “Patch Tuesday” fashion and Cisco issued a bulletin about especially disruptive DoS attacks.

Good to see it being addressed finally, I guess it took Microsoft some time and money in R&D to come up with a satisfactory solution.

I wonder if any other vendors will be following suite shortly.

On Tuesday, Microsoft responded with MS09-048, a security advisory that fixes a variety of networking vulnerabilities in Windows operating systems, including those discovered by Louis and Lee. The update implements a new feature called memory pressure protection, which automatically drops existing TCP connections and SYN requests when attacks are detected.

The update from Microsoft came during the company’s Patch Tuesday, in which it fixed a total of eight security vulnerabilities in various versions of its Windows operating system. In all, Microsoft issued five patches, which change the way Windows processes javascript, MP3 audio files and wireless signals. As always, the Sans Institute provides a helpful overview here.

Cisco issued it’s own bulletin warning that multiple products are vulnerable to DoS, or denial-of-service attacks that can be especially disruptive.

It’s often hard to fix problems like this in core components because a band-aid solution could end up breaking some of the functionality, especially with something like the TCP stack which is relied on so heavily.

Even then, a patch is released but how many people actually apply it? Cisco equipment is well known for being hard to manage/patch so I’d imagine many network devices will remain unpatched.

Source: The Register