Scientists at the University of Washington have managed to use a modified strand of DNA to infect a computer with malware. The proof of concept was designed to test a new attack vector that could possibly be used to target research facilities. Although, not many hackers will have access to DNA encoding machines.
The idea is that modern sequencers read the DNA nucleotides and encode them as A, C, G, and T. Each letter being a short form of the full chemical name. Researchers used these letters to hide code written in binary; which results in a more common stack overflow attack to later execute more code.
Admittedly, this is not going to be a very common method for attacking any particular system. Especially since the researchers needed to install a known vulnerability in their sequencer in order to test their work. In other words, the machines being tested in this experiment are a lot harder to break into than people think. Especially if the attack requires someone to edit a strand of DNA into malware.
[Source: University of Washington]