A bit flip is that unimaginably-rare event when a passing cosmic ray interacts with a computer’s memory and changes a single 1 to a 0 (or vice versa). Jaeson Schultz of Cisco presents (in a PDF) research showing that bit flips are actually common enough that they can be detected by cleverly-set-up honeypot web servers.
The idea is that certain pairs of ASCII characters are only one bit different from each other—for example, ‘n’ (010 1110) and ‘.’ (110 1110). If a bit is flipped in memory that’s being used to store a URL, the user would (through no fault of their own) be taken to the wrong site. For example,
windowsupdate.com could become
wi.dowsupdate.com. Aside from the security implications, I just think it’s fascinating that these events are common enough that the researchers were able to detect dozens of them.