Entries Tagged "denial of service"

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SMS Denial-of-Service Attack

This is a clever piece of research. Turns out you can jam cell phones with SMS messages. Text messages are transmitted on the same channel that is used to set up voice calls, so if you flood the network with one, then the other can’t happen. The researchers believe that sending 165 text messages a second is enough to disrupt all the cell phones in Manhattan.

From the paper:

ABSTRACT: Cellular networks are a critical component of the economic and social infrastructures in which we live. In addition to voice services, these networks deliver alphanumeric text messages to the vast majority of wireless subscribers. To encourage the expansion of this new service, telecommunications companies offer connections between their networks and the Internet. The ramifications of such connections, however, have not been fully recognized. In this paper, we evaluate the security impact of the SMS interface on the availability of the cellular phone network. Specifically, we demonstrate the ability to deny voice service to cities the size of Washington D.C. and Manhattan with little more than a cable modem. Moreover, attacks targeting the entire United States are feasible with resources available to medium-sized zombie networks. This analysis begins with an exploration of the structure of cellular networks. We then characterize network behavior and explore a number of reconnaissance techniques aimed at effectively targeting attacks on these systems. We conclude by discussing countermeasures that mitigate or eliminate the threats introduced by these attacks.

There’s a New York Times article and a thread on Slashdot.

Posted on October 7, 2005 at 7:43 AMView Comments

Holding Computer Files Hostage

This one has been predicted for years. Someone breaks into your network, encrypts your data files, and then demands a ransom to hand over the key.

I don’t know how the attackers did it, but below is probably the best way. A worm could be programmed to do it.

1. Break into a computer.

2. Generate a random 256-bit file-encryption key.

3. Encrypt the file-encryption key with a common RSA public key.

4. Encrypt data files with the file-encryption key.

5. Wipe data files and file-encryption key.

6. Wipe all free space on the drive.

7. Output a file containing the RSA-encrypted, file encryption key.

8. Demand ransom.

9. Receive ransom.

10. Receive encrypted file-encryption key.

11. Decrypt it and send it back.

In any situation like this, step 9 is the hardest. It’s where you’re most likely to get caught. I don’t know much about anonymous money transfer, but I don’t think Swiss bank accounts have the anonymity they used to.

You also might have to prove that you can decrypt the data, so an easy modification is to encrypt a piece of the data with another file-encryption key so you can prove to the victim that you have the RSA private key.

Internet attacks have changed over the last couple of years. They’re no longer about hackers. They’re about criminals. And we should expect to see more of this sort of thing in the future.

Posted on May 30, 2005 at 8:18 AMView Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.