Cosmic rays

A common joke among programmers is that "a cosmic ray" changed a bit in memory and caused a bug. Often this is used as the humorous last resort excuse. Even though the probability of this is extremely low, this does actually happen in real life. Memory chips can alter it's state due to cosmic rays. And this is why computers whose operation is critical under all conditions use Error Correcting Memory which can detect and correct so called soft errors in the memory.

The impact of cosmic rays on memory chips have basically been known for decades. The consequence has usually been thought of as incorrect behaviour. However, a recent Princeton study shows that these soft errors, which can be induced by heat, represent a security threat even to Virtual Machines such as the Java VM and the .NET VM. The researchers are particularly concerned with the security of so called smart cards which are small and increasingly used to verify the identity of users.

Some more links:
IBM Research on the impact of cosmic rays on memory chips
Corsairs Whitepaper on ECC Memory