How secure is a bluetooth keyboard against password sniffing?

Solution 1:

http://en.wikipedia.org/wiki/Bluetooth#Security

While Bluetooth has its benefits, it is susceptible to denial of service attacks, eavesdropping, man-in-the-middle attacks, message modification, and resource misappropriation.

Solution 2:

I'd suggest looking at this publication by the NIST. It provides some pretty useful information on Bluetooth security. The encryption protocol of bluetooth is E0 which is 128 bit.

http://csrc.nist.gov/publications/nistpubs/800-121-rev1/sp800-121_rev1.pdf

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Solution 3:

Although bluetooth may not be the most secure protocol, you have to put things in perspective: Bluetooth has a relativity short transmit range. This means that if you were to use bluetooth keyboards in a building, a person would have to be in the same room or close to the room to actually do anything malicious.

Just because a certain technology is insecure, doesn't mean that it is useless.