The legal status of cryptocurrencies varies substantially from country to country and is still undefined or changing in many of them.Only yesterday, the head of the US Securities and Exchange Commission warned bitcoin and other cryptocurrency investors to be aware of scams and criminal activity in the sector.In the financial regulator’s strongest statement yet, SEC chair Jay Clayton said: “If a promoter guarantees returns, if an opportunity sounds too good to be true, or if you are pressured to act quickly, please exercise extreme caution and be aware of the risk that your investment may be lost.”Anyone thinking of investing in Bitcoin or another cryptocurrency should be very careful.Their values are volatile, with the ability to plummet as quickly as they shoot up.And investors are frequently targeted by hackers and other criminals who seek to steal their crypto-cash online.Be especially careful if you are using direct, peer-to-peer platforms to sell and buy cryptocurrencies.These are the equivalent of something like Gumtree for Bitcoin – you never know who you might be dealing with.