A breakthrough study has discovered all octopuses, cuttlefish and some squid are venomous.

It was previously thought that only the blue-ringed octopus was the one to watch out for.

The study by scientists from the University of Melbourne , University of Brussels and Museum Victoria found that while the blue-ringed octopus remain the only species dangerous to humans, other groups have been quietly using their venom for predation.

Dr Bryan Fry from the University of Melbourne said venoms were toxic proteins that performed functions such as paralysing the nervous system.

"We hope that by understanding the structure and mode of action of venom proteins we can benefit drug design for a range of conditions such as pain management, allergies and cancer," Dr Fry said.

Octopuses, cuttlefish and squid - known as cephalopods - remain an untapped resource for drug development.

The team analysed tissue samples from cephalopods from Hong Kong , the Coral Sea, the Great Barrier Reef and Antarctica.

The different species' genes were then studied for venom protection and it was found that a venomous ancestor produced one set of venom proteins, but over time additional proteins had added to the chemical arsenal.

Scientists will now work on understanding why different types of venomous animals seem to settle on similar venom protein composition.

The physical and chemical properties which make them predisposed to be useful as toxin will also be studied.