New Low Bandwidth Denial of Service Attacks

An anonymous reader writes "A paper from Rice University appearing at the 2003 ACM Sigcomm Conference presents a new denial of service attack where the attacker only needs to send at a low rate to shutdown TCP flows. The trick exploits the retransmission timeout mechanism in TCP. By sending small bursts of packets at just the right frequency, the attacker can cause all TCP flows sharing a bottleneck link to simultaneously stop indefinitely. And because the attacker only needs to burst periodically, the attacker will not be distinguishable from normal hosts. The presentation, and other presentations from the conference, are available online (live streaming)."

Comments

Re:yay (faker!)

[Zathrus]

No. Modems stopped increasing in baud at 2400, and then used various encoding methods (trellis, QAM, etc.) to squeeze more than 1 bit/baud. A 9600 bps modem, for instance, averages 4 bits/baud.

Well. Almost.

Better quality phone lines can support >2400 baud, but not by much. A 28800 bps connection is running at 3429 baud IIRC, and varying line conditions will reduce that baud rate, thus reducing your effective bps.

Compression is on top of all of this. It's an entirely different issue, and if you transfer straight text over a 28.8k modem you can get considerably more than 28.8kbps out of the modem.

You got the broad stuff right though, which is a lot more than most people grok.