1024

The first allowable tcp or udp port to be bound by an non superuser under most unices. I don't believe this is the case with any of the microsoft products. So the potential for anonymous DoS attacks from such machines is limitless.

There are several interesting coincidences with regard to this number; the 10th power of 2, or the 10th member, excluding 1, of the sequence 1, 2, 4, 8... is 1024, which can be broken into '10', '2' and '4'

As if that were not enough, 1024 is also within a very few percent of a decimal thousand, which is the trait that makes it such a convenient unit for disc and memory size - it can be approximated at 1,000 by the general population without losing much accuracy. This property, of course, is a source of major confusion when quickly reading the output of programs that (eg) display the size of directories in units of 1 MB = 1048288 and the size of the files within the directory in units of 1 KB=1024 bytes.