Abstract
A DNA microdot offers a novel way in which to communicate secret information. It is an extension of the more traditional microdot, a greatly reduced photograph of a secret document which replaced a full stop somewhere in an innocent-looking letter. The DNA microdot appears to be the secure modern alternative, exploiting the complexity of DNA in which a coded secret message is hidden. An enemy can only unlock the secret information by first knowing that an intercepted letter is impregnated with microdot DNA, and secondly by finding the message amongst a huge amount of background DNA used to mask the secret information. Using software developed to identify horizontally acquired DNA, we show that this apparently insurmountable task is in fact possible. With the increased speed of DNA sequencing, the information contained in the DNA microdot is far from secure.